Adding upstream version 115.7.0esr.upstream/115.7.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

14 files changed, 3427 insertions, 0 deletions

diff --git a/third_party/rust/clap_derive/src/attrs.rs b/third_party/rust/clap_derive/src/attrs.rs
new file mode 100644
index 0000000000..aaee167e31
--- /dev/null
+++ b/third_party/rust/clap_derive/src/attrs.rs
@@ -0,0 +1,985 @@
+// Copyright 2018 Guillaume Pinot (@TeXitoi) <texitoi@texitoi.eu>,
+// Kevin Knapp (@kbknapp) <kbknapp@gmail.com>, and
+// Ana Hobden (@hoverbear) <operator@hoverbear.org>
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+//
+// This work was derived from Structopt (https://github.com/TeXitoi/structopt)
+// commit#ea76fa1b1b273e65e3b0b1046643715b49bec51f which is licensed under the
+// MIT/Apache 2.0 license.
+
+use crate::{
+    parse::*,
+    utils::{process_doc_comment, Sp, Ty},
+};
+
+use std::env;
+
+use heck::{ToKebabCase, ToLowerCamelCase, ToShoutySnakeCase, ToSnakeCase, ToUpperCamelCase};
+use proc_macro2::{self, Span, TokenStream};
+use proc_macro_error::abort;
+use quote::{quote, quote_spanned, ToTokens};
+use syn::{
+    self, ext::IdentExt, spanned::Spanned, Attribute, Expr, Field, Ident, LitStr, MetaNameValue,
+    Type, Variant,
+};
+
+/// Default casing style for generated arguments.
+pub const DEFAULT_CASING: CasingStyle = CasingStyle::Kebab;
+
+/// Default casing style for environment variables
+pub const DEFAULT_ENV_CASING: CasingStyle = CasingStyle::ScreamingSnake;
+
+#[derive(Clone)]
+pub struct Attrs {
+    name: Name,
+    casing: Sp<CasingStyle>,
+    env_casing: Sp<CasingStyle>,
+    ty: Option<Type>,
+    doc_comment: Vec<Method>,
+    methods: Vec<Method>,
+    parser: Sp<Parser>,
+    verbatim_doc_comment: Option<Ident>,
+    next_display_order: Option<Method>,
+    next_help_heading: Option<Method>,
+    help_heading: Option<Method>,
+    is_enum: bool,
+    has_custom_parser: bool,
+    kind: Sp<Kind>,
+}
+
+impl Attrs {
+    pub fn from_struct(
+        span: Span,
+        attrs: &[Attribute],
+        name: Name,
+        argument_casing: Sp<CasingStyle>,
+        env_casing: Sp<CasingStyle>,
+    ) -> Self {
+        let mut res = Self::new(span, name, None, argument_casing, env_casing);
+        res.push_attrs(attrs);
+        res.push_doc_comment(attrs, "about");
+
+        if res.has_custom_parser {
+            abort!(
+                res.parser.span(),
+                "`parse` attribute is only allowed on fields"
+            );
+        }
+        match &*res.kind {
+            Kind::Subcommand(_) => abort!(res.kind.span(), "subcommand is only allowed on fields"),
+            Kind::Skip(_) => abort!(res.kind.span(), "skip is only allowed on fields"),
+            Kind::Arg(_) => res,
+            Kind::FromGlobal(_) => abort!(res.kind.span(), "from_global is only allowed on fields"),
+            Kind::Flatten => abort!(res.kind.span(), "flatten is only allowed on fields"),
+            Kind::ExternalSubcommand => abort!(
+                res.kind.span(),
+                "external_subcommand is only allowed on fields"
+            ),
+        }
+    }
+
+    pub fn from_variant(
+        variant: &Variant,
+        struct_casing: Sp<CasingStyle>,
+        env_casing: Sp<CasingStyle>,
+    ) -> Self {
+        let name = variant.ident.clone();
+        let mut res = Self::new(
+            variant.span(),
+            Name::Derived(name),
+            None,
+            struct_casing,
+            env_casing,
+        );
+        res.push_attrs(&variant.attrs);
+        res.push_doc_comment(&variant.attrs, "about");
+
+        match &*res.kind {
+            Kind::Flatten => {
+                if res.has_custom_parser {
+                    abort!(
+                        res.parser.span(),
+                        "parse attribute is not allowed for flattened entry"
+                    );
+                }
+                if res.has_explicit_methods() {
+                    abort!(
+                        res.kind.span(),
+                        "methods are not allowed for flattened entry"
+                    );
+                }
+
+                // ignore doc comments
+                res.doc_comment = vec![];
+            }
+
+            Kind::ExternalSubcommand => (),
+
+            Kind::Subcommand(_) => {
+                if res.has_custom_parser {
+                    abort!(
+                        res.parser.span(),
+                        "parse attribute is not allowed for subcommand"
+                    );
+                }
+
+                use syn::Fields::*;
+                use syn::FieldsUnnamed;
+                let field_ty = match variant.fields {
+                    Named(_) => {
+                        abort!(variant.span(), "structs are not allowed for subcommand");
+                    }
+                    Unit => abort!(variant.span(), "unit-type is not allowed for subcommand"),
+                    Unnamed(FieldsUnnamed { ref unnamed, .. }) if unnamed.len() == 1 => {
+                        &unnamed[0].ty
+                    }
+                    Unnamed(..) => {
+                        abort!(
+                            variant,
+                            "non single-typed tuple is not allowed for subcommand"
+                        )
+                    }
+                };
+                let ty = Ty::from_syn_ty(field_ty);
+                match *ty {
+                    Ty::OptionOption => {
+                        abort!(
+                            field_ty,
+                            "Option<Option<T>> type is not allowed for subcommand"
+                        );
+                    }
+                    Ty::OptionVec => {
+                        abort!(
+                            field_ty,
+                            "Option<Vec<T>> type is not allowed for subcommand"
+                        );
+                    }
+                    _ => (),
+                }
+
+                res.kind = Sp::new(Kind::Subcommand(ty), res.kind.span());
+            }
+            Kind::Skip(_) => (),
+            Kind::FromGlobal(_) => {
+                abort!(res.kind.span(), "from_global is not supported on variants");
+            }
+            Kind::Arg(_) => (),
+        }
+
+        res
+    }
+
+    pub fn from_arg_enum_variant(
+        variant: &Variant,
+        argument_casing: Sp<CasingStyle>,
+        env_casing: Sp<CasingStyle>,
+    ) -> Self {
+        let mut res = Self::new(
+            variant.span(),
+            Name::Derived(variant.ident.clone()),
+            None,
+            argument_casing,
+            env_casing,
+        );
+        res.push_attrs(&variant.attrs);
+        res.push_doc_comment(&variant.attrs, "help");
+
+        if res.has_custom_parser {
+            abort!(
+                res.parser.span(),
+                "`parse` attribute is only allowed on fields"
+            );
+        }
+        match &*res.kind {
+            Kind::Subcommand(_) => abort!(res.kind.span(), "subcommand is only allowed on fields"),
+            Kind::Skip(_) => res,
+            Kind::Arg(_) => res,
+            Kind::FromGlobal(_) => abort!(res.kind.span(), "from_global is only allowed on fields"),
+            Kind::Flatten => abort!(res.kind.span(), "flatten is only allowed on fields"),
+            Kind::ExternalSubcommand => abort!(
+                res.kind.span(),
+                "external_subcommand is only allowed on fields"
+            ),
+        }
+    }
+
+    pub fn from_field(
+        field: &Field,
+        struct_casing: Sp<CasingStyle>,
+        env_casing: Sp<CasingStyle>,
+    ) -> Self {
+        let name = field.ident.clone().unwrap();
+        let mut res = Self::new(
+            field.span(),
+            Name::Derived(name),
+            Some(field.ty.clone()),
+            struct_casing,
+            env_casing,
+        );
+        res.push_attrs(&field.attrs);
+        res.push_doc_comment(&field.attrs, "help");
+
+        match &*res.kind {
+            Kind::Flatten => {
+                if res.has_custom_parser {
+                    abort!(
+                        res.parser.span(),
+                        "parse attribute is not allowed for flattened entry"
+                    );
+                }
+                if res.has_explicit_methods() {
+                    abort!(
+                        res.kind.span(),
+                        "methods are not allowed for flattened entry"
+                    );
+                }
+
+                // ignore doc comments
+                res.doc_comment = vec![];
+            }
+
+            Kind::ExternalSubcommand => {
+                abort! { res.kind.span(),
+                    "`external_subcommand` can be used only on enum variants"
+                }
+            }
+
+            Kind::Subcommand(_) => {
+                if res.has_custom_parser {
+                    abort!(
+                        res.parser.span(),
+                        "parse attribute is not allowed for subcommand"
+                    );
+                }
+                if res.has_explicit_methods() {
+                    abort!(
+                        res.kind.span(),
+                        "methods in attributes are not allowed for subcommand"
+                    );
+                }
+
+                let ty = Ty::from_syn_ty(&field.ty);
+                match *ty {
+                    Ty::OptionOption => {
+                        abort!(
+                            field.ty,
+                            "Option<Option<T>> type is not allowed for subcommand"
+                        );
+                    }
+                    Ty::OptionVec => {
+                        abort!(
+                            field.ty,
+                            "Option<Vec<T>> type is not allowed for subcommand"
+                        );
+                    }
+                    _ => (),
+                }
+
+                res.kind = Sp::new(Kind::Subcommand(ty), res.kind.span());
+            }
+            Kind::Skip(_) => {
+                if res.has_explicit_methods() {
+                    abort!(
+                        res.kind.span(),
+                        "methods are not allowed for skipped fields"
+                    );
+                }
+            }
+            Kind::FromGlobal(orig_ty) => {
+                let ty = Ty::from_syn_ty(&field.ty);
+                res.kind = Sp::new(Kind::FromGlobal(ty), orig_ty.span());
+            }
+            Kind::Arg(orig_ty) => {
+                let mut ty = Ty::from_syn_ty(&field.ty);
+                if res.has_custom_parser {
+                    match *ty {
+                        Ty::Option | Ty::Vec | Ty::OptionVec => (),
+                        _ => ty = Sp::new(Ty::Other, ty.span()),
+                    }
+                }
+
+                match *ty {
+                    Ty::Bool => {
+                        if res.is_positional() && !res.has_custom_parser {
+                            abort!(field.ty,
+                                "`bool` cannot be used as positional parameter with default parser";
+                                help = "if you want to create a flag add `long` or `short`";
+                                help = "If you really want a boolean parameter \
+                                    add an explicit parser, for example `parse(try_from_str)`";
+                                note = "see also https://github.com/clap-rs/clap/blob/master/examples/derive_ref/custom-bool.md";
+                            )
+                        }
+                        if res.is_enum {
+                            abort!(field.ty, "`arg_enum` is meaningless for bool")
+                        }
+                        if let Some(m) = res.find_default_method() {
+                            abort!(m.name, "default_value is meaningless for bool")
+                        }
+                        if let Some(m) = res.find_method("required") {
+                            abort!(m.name, "required is meaningless for bool")
+                        }
+                    }
+                    Ty::Option => {
+                        if let Some(m) = res.find_default_method() {
+                            abort!(m.name, "default_value is meaningless for Option")
+                        }
+                    }
+                    Ty::OptionOption => {
+                        if res.is_positional() {
+                            abort!(
+                                field.ty,
+                                "Option<Option<T>> type is meaningless for positional argument"
+                            )
+                        }
+                    }
+                    Ty::OptionVec => {
+                        if res.is_positional() {
+                            abort!(
+                                field.ty,
+                                "Option<Vec<T>> type is meaningless for positional argument"
+                            )
+                        }
+                    }
+
+                    _ => (),
+                }
+                res.kind = Sp::new(Kind::Arg(ty), orig_ty.span());
+            }
+        }
+
+        res
+    }
+
+    fn new(
+        default_span: Span,
+        name: Name,
+        ty: Option<Type>,
+        casing: Sp<CasingStyle>,
+        env_casing: Sp<CasingStyle>,
+    ) -> Self {
+        Self {
+            name,
+            ty,
+            casing,
+            env_casing,
+            doc_comment: vec![],
+            methods: vec![],
+            parser: Parser::default_spanned(default_span),
+            verbatim_doc_comment: None,
+            next_display_order: None,
+            next_help_heading: None,
+            help_heading: None,
+            is_enum: false,
+            has_custom_parser: false,
+            kind: Sp::new(Kind::Arg(Sp::new(Ty::Other, default_span)), default_span),
+        }
+    }
+
+    fn push_method(&mut self, name: Ident, arg: impl ToTokens) {
+        if name == "name" {
+            self.name = Name::Assigned(quote!(#arg));
+        } else {
+            self.methods.push(Method::new(name, quote!(#arg)));
+        }
+    }
+
+    fn push_attrs(&mut self, attrs: &[Attribute]) {
+        use ClapAttr::*;
+
+        let parsed = parse_clap_attributes(attrs);
+        for attr in &parsed {
+            let attr = attr.clone();
+            match attr {
+                Short(ident) => {
+                    self.push_method(ident, self.name.clone().translate_char(*self.casing));
+                }
+
+                Long(ident) => {
+                    self.push_method(ident, self.name.clone().translate(*self.casing));
+                }
+
+                Env(ident) => {
+                    self.push_method(ident, self.name.clone().translate(*self.env_casing));
+                }
+
+                ArgEnum(_) => self.is_enum = true,
+
+                FromGlobal(ident) => {
+                    let ty = Sp::call_site(Ty::Other);
+                    let kind = Sp::new(Kind::FromGlobal(ty), ident.span());
+                    self.set_kind(kind);
+                }
+
+                Subcommand(ident) => {
+                    let ty = Sp::call_site(Ty::Other);
+                    let kind = Sp::new(Kind::Subcommand(ty), ident.span());
+                    self.set_kind(kind);
+                }
+
+                ExternalSubcommand(ident) => {
+                    let kind = Sp::new(Kind::ExternalSubcommand, ident.span());
+                    self.set_kind(kind);
+                }
+
+                Flatten(ident) => {
+                    let kind = Sp::new(Kind::Flatten, ident.span());
+                    self.set_kind(kind);
+                }
+
+                Skip(ident, expr) => {
+                    let kind = Sp::new(Kind::Skip(expr), ident.span());
+                    self.set_kind(kind);
+                }
+
+                VerbatimDocComment(ident) => self.verbatim_doc_comment = Some(ident),
+
+                DefaultValueT(ident, expr) => {
+                    let ty = if let Some(ty) = self.ty.as_ref() {
+                        ty
+                    } else {
+                        abort!(
+                            ident,
+                            "#[clap(default_value_t)] (without an argument) can be used \
+                            only on field level";
+
+                            note = "see \
+                                https://github.com/clap-rs/clap/blob/master/examples/derive_ref/README.md#magic-attributes")
+                    };
+
+                    let val = if let Some(expr) = expr {
+                        quote!(#expr)
+                    } else {
+                        quote!(<#ty as ::std::default::Default>::default())
+                    };
+
+                    let val = if parsed.iter().any(|a| matches!(a, ArgEnum(_))) {
+                        quote_spanned!(ident.span()=> {
+                            {
+                                let val: #ty = #val;
+                                clap::ArgEnum::to_possible_value(&val).unwrap().get_name()
+                            }
+                        })
+                    } else {
+                        quote_spanned!(ident.span()=> {
+                            clap::lazy_static::lazy_static! {
+                                static ref DEFAULT_VALUE: &'static str = {
+                                    let val: #ty = #val;
+                                    let s = ::std::string::ToString::to_string(&val);
+                                    ::std::boxed::Box::leak(s.into_boxed_str())
+                                };
+                            }
+                            *DEFAULT_VALUE
+                        })
+                    };
+
+                    let raw_ident = Ident::new("default_value", ident.span());
+                    self.methods.push(Method::new(raw_ident, val));
+                }
+
+                DefaultValueOsT(ident, expr) => {
+                    let ty = if let Some(ty) = self.ty.as_ref() {
+                        ty
+                    } else {
+                        abort!(
+                            ident,
+                            "#[clap(default_value_os_t)] (without an argument) can be used \
+                            only on field level";
+
+                            note = "see \
+                                https://github.com/clap-rs/clap/blob/master/examples/derive_ref/README.md#magic-attributes")
+                    };
+
+                    let val = if let Some(expr) = expr {
+                        quote!(#expr)
+                    } else {
+                        quote!(<#ty as ::std::default::Default>::default())
+                    };
+
+                    let val = if parsed.iter().any(|a| matches!(a, ArgEnum(_))) {
+                        quote_spanned!(ident.span()=> {
+                            {
+                                let val: #ty = #val;
+                                clap::ArgEnum::to_possible_value(&val).unwrap().get_name()
+                            }
+                        })
+                    } else {
+                        quote_spanned!(ident.span()=> {
+                            clap::lazy_static::lazy_static! {
+                                static ref DEFAULT_VALUE: &'static ::std::ffi::OsStr = {
+                                    let val: #ty = #val;
+                                    let s: ::std::ffi::OsString = val.into();
+                                    ::std::boxed::Box::leak(s.into_boxed_os_str())
+                                };
+                            }
+                            *DEFAULT_VALUE
+                        })
+                    };
+
+                    let raw_ident = Ident::new("default_value_os", ident.span());
+                    self.methods.push(Method::new(raw_ident, val));
+                }
+
+                NextDisplayOrder(ident, expr) => {
+                    self.next_display_order = Some(Method::new(ident, quote!(#expr)));
+                }
+
+                HelpHeading(ident, expr) => {
+                    self.help_heading = Some(Method::new(ident, quote!(#expr)));
+                }
+                NextHelpHeading(ident, expr) => {
+                    self.next_help_heading = Some(Method::new(ident, quote!(#expr)));
+                }
+
+                About(ident) => {
+                    if let Some(method) = Method::from_env(ident, "CARGO_PKG_DESCRIPTION") {
+                        self.methods.push(method);
+                    }
+                }
+
+                Author(ident) => {
+                    if let Some(method) = Method::from_env(ident, "CARGO_PKG_AUTHORS") {
+                        self.methods.push(method);
+                    }
+                }
+
+                Version(ident) => {
+                    if let Some(method) = Method::from_env(ident, "CARGO_PKG_VERSION") {
+                        self.methods.push(method);
+                    }
+                }
+
+                NameLitStr(name, lit) => {
+                    self.push_method(name, lit);
+                }
+
+                NameExpr(name, expr) => {
+                    self.push_method(name, expr);
+                }
+
+                MethodCall(name, args) => self.push_method(name, quote!(#(#args),*)),
+
+                RenameAll(_, casing_lit) => {
+                    self.casing = CasingStyle::from_lit(casing_lit);
+                }
+
+                RenameAllEnv(_, casing_lit) => {
+                    self.env_casing = CasingStyle::from_lit(casing_lit);
+                }
+
+                Parse(ident, spec) => {
+                    self.has_custom_parser = true;
+                    self.parser = Parser::from_spec(ident, spec);
+                }
+            }
+        }
+    }
+
+    fn push_doc_comment(&mut self, attrs: &[Attribute], name: &str) {
+        use syn::Lit::*;
+        use syn::Meta::*;
+
+        let comment_parts: Vec<_> = attrs
+            .iter()
+            .filter(|attr| attr.path.is_ident("doc"))
+            .filter_map(|attr| {
+                if let Ok(NameValue(MetaNameValue { lit: Str(s), .. })) = attr.parse_meta() {
+                    Some(s.value())
+                } else {
+                    // non #[doc = "..."] attributes are not our concern
+                    // we leave them for rustc to handle
+                    None
+                }
+            })
+            .collect();
+
+        self.doc_comment =
+            process_doc_comment(comment_parts, name, self.verbatim_doc_comment.is_none());
+    }
+
+    fn set_kind(&mut self, kind: Sp<Kind>) {
+        if let Kind::Arg(_) = *self.kind {
+            self.kind = kind;
+        } else {
+            abort!(
+                kind.span(),
+                "`subcommand`, `flatten`, `external_subcommand` and `skip` cannot be used together"
+            );
+        }
+    }
+
+    pub fn find_method(&self, name: &str) -> Option<&Method> {
+        self.methods.iter().find(|m| m.name == name)
+    }
+
+    pub fn find_default_method(&self) -> Option<&Method> {
+        self.methods
+            .iter()
+            .find(|m| m.name == "default_value" || m.name == "default_value_os")
+    }
+
+    /// generate methods from attributes on top of struct or enum
+    pub fn initial_top_level_methods(&self) -> TokenStream {
+        let next_display_order = self.next_display_order.as_ref().into_iter();
+        let next_help_heading = self.next_help_heading.as_ref().into_iter();
+        let help_heading = self.help_heading.as_ref().into_iter();
+        quote!(
+            #(#next_display_order)*
+            #(#next_help_heading)*
+            #(#help_heading)*
+        )
+    }
+
+    pub fn final_top_level_methods(&self) -> TokenStream {
+        let methods = &self.methods;
+        let doc_comment = &self.doc_comment;
+
+        quote!( #(#doc_comment)* #(#methods)*)
+    }
+
+    /// generate methods on top of a field
+    pub fn field_methods(&self, supports_long_help: bool) -> proc_macro2::TokenStream {
+        let methods = &self.methods;
+        let help_heading = self.help_heading.as_ref().into_iter();
+        match supports_long_help {
+            true => {
+                let doc_comment = &self.doc_comment;
+                quote!( #(#doc_comment)* #(#help_heading)* #(#methods)* )
+            }
+            false => {
+                let doc_comment = self
+                    .doc_comment
+                    .iter()
+                    .filter(|mth| mth.name != "long_help");
+                quote!( #(#doc_comment)* #(#help_heading)* #(#methods)* )
+            }
+        }
+    }
+
+    pub fn next_display_order(&self) -> TokenStream {
+        let next_display_order = self.next_display_order.as_ref().into_iter();
+        quote!( #(#next_display_order)* )
+    }
+
+    pub fn next_help_heading(&self) -> TokenStream {
+        let next_help_heading = self.next_help_heading.as_ref().into_iter();
+        let help_heading = self.help_heading.as_ref().into_iter();
+        quote!( #(#next_help_heading)*  #(#help_heading)* )
+    }
+
+    #[cfg(feature = "unstable-v4")]
+    pub fn id(&self) -> TokenStream {
+        self.name.clone().raw()
+    }
+
+    #[cfg(not(feature = "unstable-v4"))]
+    pub fn id(&self) -> TokenStream {
+        self.cased_name()
+    }
+
+    pub fn cased_name(&self) -> TokenStream {
+        self.name.clone().translate(*self.casing)
+    }
+
+    pub fn value_name(&self) -> TokenStream {
+        self.name.clone().translate(CasingStyle::ScreamingSnake)
+    }
+
+    pub fn parser(&self) -> &Sp<Parser> {
+        &self.parser
+    }
+
+    pub fn kind(&self) -> Sp<Kind> {
+        self.kind.clone()
+    }
+
+    pub fn is_enum(&self) -> bool {
+        self.is_enum
+    }
+
+    pub fn ignore_case(&self) -> TokenStream {
+        let method = self.find_method("ignore_case");
+
+        if let Some(method) = method {
+            method.args.clone()
+        } else {
+            quote! { false }
+        }
+    }
+
+    pub fn casing(&self) -> Sp<CasingStyle> {
+        self.casing.clone()
+    }
+
+    pub fn env_casing(&self) -> Sp<CasingStyle> {
+        self.env_casing.clone()
+    }
+
+    pub fn is_positional(&self) -> bool {
+        self.methods
+            .iter()
+            .all(|m| m.name != "long" && m.name != "short")
+    }
+
+    pub fn has_explicit_methods(&self) -> bool {
+        self.methods
+            .iter()
+            .any(|m| m.name != "help" && m.name != "long_help")
+    }
+}
+
+#[allow(clippy::large_enum_variant)]
+#[derive(Clone)]
+pub enum Kind {
+    Arg(Sp<Ty>),
+    FromGlobal(Sp<Ty>),
+    Subcommand(Sp<Ty>),
+    Flatten,
+    Skip(Option<Expr>),
+    ExternalSubcommand,
+}
+
+#[derive(Clone)]
+pub struct Method {
+    name: Ident,
+    args: TokenStream,
+}
+
+impl Method {
+    pub fn new(name: Ident, args: TokenStream) -> Self {
+        Method { name, args }
+    }
+
+    fn from_env(ident: Ident, env_var: &str) -> Option<Self> {
+        let mut lit = match env::var(env_var) {
+            Ok(val) => {
+                if val.is_empty() {
+                    return None;
+                }
+                LitStr::new(&val, ident.span())
+            }
+            Err(_) => {
+                abort!(ident,
+                    "cannot derive `{}` from Cargo.toml", ident;
+                    note = "`{}` environment variable is not set", env_var;
+                    help = "use `{} = \"...\"` to set {} manually", ident, ident;
+                );
+            }
+        };
+
+        if ident == "author" {
+            let edited = process_author_str(&lit.value());
+            lit = LitStr::new(&edited, lit.span());
+        }
+
+        Some(Method::new(ident, quote!(#lit)))
+    }
+}
+
+impl ToTokens for Method {
+    fn to_tokens(&self, ts: &mut proc_macro2::TokenStream) {
+        let Method { ref name, ref args } = self;
+
+        let tokens = quote!( .#name(#args) );
+
+        tokens.to_tokens(ts);
+    }
+}
+
+/// replace all `:` with `, ` when not inside the `<>`
+///
+/// `"author1:author2:author3" => "author1, author2, author3"`
+/// `"author1 <http://website1.com>:author2" => "author1 <http://website1.com>, author2"
+fn process_author_str(author: &str) -> String {
+    let mut res = String::with_capacity(author.len());
+    let mut inside_angle_braces = 0usize;
+
+    for ch in author.chars() {
+        if inside_angle_braces > 0 && ch == '>' {
+            inside_angle_braces -= 1;
+            res.push(ch);
+        } else if ch == '<' {
+            inside_angle_braces += 1;
+            res.push(ch);
+        } else if inside_angle_braces == 0 && ch == ':' {
+            res.push_str(", ");
+        } else {
+            res.push(ch);
+        }
+    }
+
+    res
+}
+
+#[derive(Clone)]
+pub struct Parser {
+    pub kind: Sp<ParserKind>,
+    pub func: TokenStream,
+}
+
+impl Parser {
+    fn default_spanned(span: Span) -> Sp<Self> {
+        let kind = Sp::new(ParserKind::TryFromStr, span);
+        let func = quote_spanned!(span=> ::std::str::FromStr::from_str);
+        Sp::new(Parser { kind, func }, span)
+    }
+
+    fn from_spec(parse_ident: Ident, spec: ParserSpec) -> Sp<Self> {
+        use self::ParserKind::*;
+
+        let kind = match &*spec.kind.to_string() {
+            "from_str" => FromStr,
+            "try_from_str" => TryFromStr,
+            "from_os_str" => FromOsStr,
+            "try_from_os_str" => TryFromOsStr,
+            "from_occurrences" => FromOccurrences,
+            "from_flag" => FromFlag,
+            s => abort!(spec.kind.span(), "unsupported parser `{}`", s),
+        };
+
+        let func = match spec.parse_func {
+            None => match kind {
+                FromStr | FromOsStr => {
+                    quote_spanned!(spec.kind.span()=> ::std::convert::From::from)
+                }
+                TryFromStr => quote_spanned!(spec.kind.span()=> ::std::str::FromStr::from_str),
+                TryFromOsStr => abort!(
+                    spec.kind.span(),
+                    "you must set parser for `try_from_os_str` explicitly"
+                ),
+                FromOccurrences => quote_spanned!(spec.kind.span()=> { |v| v as _ }),
+                FromFlag => quote_spanned!(spec.kind.span()=> ::std::convert::From::from),
+            },
+
+            Some(func) => match func {
+                Expr::Path(_) => quote!(#func),
+                _ => abort!(func, "`parse` argument must be a function path"),
+            },
+        };
+
+        let kind = Sp::new(kind, spec.kind.span());
+        let parser = Parser { kind, func };
+        Sp::new(parser, parse_ident.span())
+    }
+}
+
+#[derive(Debug, PartialEq, Clone)]
+pub enum ParserKind {
+    FromStr,
+    TryFromStr,
+    FromOsStr,
+    TryFromOsStr,
+    FromOccurrences,
+    FromFlag,
+}
+
+/// Defines the casing for the attributes long representation.
+#[derive(Copy, Clone, Debug, PartialEq)]
+pub enum CasingStyle {
+    /// Indicate word boundaries with uppercase letter, excluding the first word.
+    Camel,
+    /// Keep all letters lowercase and indicate word boundaries with hyphens.
+    Kebab,
+    /// Indicate word boundaries with uppercase letter, including the first word.
+    Pascal,
+    /// Keep all letters uppercase and indicate word boundaries with underscores.
+    ScreamingSnake,
+    /// Keep all letters lowercase and indicate word boundaries with underscores.
+    Snake,
+    /// Keep all letters lowercase and remove word boundaries.
+    Lower,
+    /// Keep all letters uppercase and remove word boundaries.
+    Upper,
+    /// Use the original attribute name defined in the code.
+    Verbatim,
+}
+
+impl CasingStyle {
+    fn from_lit(name: LitStr) -> Sp<Self> {
+        use self::CasingStyle::*;
+
+        let normalized = name.value().to_upper_camel_case().to_lowercase();
+        let cs = |kind| Sp::new(kind, name.span());
+
+        match normalized.as_ref() {
+            "camel" | "camelcase" => cs(Camel),
+            "kebab" | "kebabcase" => cs(Kebab),
+            "pascal" | "pascalcase" => cs(Pascal),
+            "screamingsnake" | "screamingsnakecase" => cs(ScreamingSnake),
+            "snake" | "snakecase" => cs(Snake),
+            "lower" | "lowercase" => cs(Lower),
+            "upper" | "uppercase" => cs(Upper),
+            "verbatim" | "verbatimcase" => cs(Verbatim),
+            s => abort!(name, "unsupported casing: `{}`", s),
+        }
+    }
+}
+
+#[derive(Clone)]
+pub enum Name {
+    Derived(Ident),
+    Assigned(TokenStream),
+}
+
+impl Name {
+    #[cfg(feature = "unstable-v4")]
+    pub fn raw(self) -> TokenStream {
+        match self {
+            Name::Assigned(tokens) => tokens,
+            Name::Derived(ident) => {
+                let s = ident.unraw().to_string();
+                quote_spanned!(ident.span()=> #s)
+            }
+        }
+    }
+
+    pub fn translate(self, style: CasingStyle) -> TokenStream {
+        use CasingStyle::*;
+
+        match self {
+            Name::Assigned(tokens) => tokens,
+            Name::Derived(ident) => {
+                let s = ident.unraw().to_string();
+                let s = match style {
+                    Pascal => s.to_upper_camel_case(),
+                    Kebab => s.to_kebab_case(),
+                    Camel => s.to_lower_camel_case(),
+                    ScreamingSnake => s.to_shouty_snake_case(),
+                    Snake => s.to_snake_case(),
+                    Lower => s.to_snake_case().replace('_', ""),
+                    Upper => s.to_shouty_snake_case().replace('_', ""),
+                    Verbatim => s,
+                };
+                quote_spanned!(ident.span()=> #s)
+            }
+        }
+    }
+
+    pub fn translate_char(self, style: CasingStyle) -> TokenStream {
+        use CasingStyle::*;
+
+        match self {
+            Name::Assigned(tokens) => quote!( (#tokens).chars().next().unwrap() ),
+            Name::Derived(ident) => {
+                let s = ident.unraw().to_string();
+                let s = match style {
+                    Pascal => s.to_upper_camel_case(),
+                    Kebab => s.to_kebab_case(),
+                    Camel => s.to_lower_camel_case(),
+                    ScreamingSnake => s.to_shouty_snake_case(),
+                    Snake => s.to_snake_case(),
+                    Lower => s.to_snake_case(),
+                    Upper => s.to_shouty_snake_case(),
+                    Verbatim => s,
+                };
+
+                let s = s.chars().next().unwrap();
+                quote_spanned!(ident.span()=> #s)
+            }
+        }
+    }
+}
diff --git a/third_party/rust/clap_derive/src/derives/arg_enum.rs b/third_party/rust/clap_derive/src/derives/arg_enum.rs
new file mode 100644
index 0000000000..77067e9029
--- /dev/null
+++ b/third_party/rust/clap_derive/src/derives/arg_enum.rs
@@ -0,0 +1,123 @@
+// Copyright 2018 Guillaume Pinot (@TeXitoi) <texitoi@texitoi.eu>,
+// Kevin Knapp (@kbknapp) <kbknapp@gmail.com>, and
+// Ana Hobden (@hoverbear) <operator@hoverbear.org>
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use crate::{
+    attrs::{Attrs, Kind, Name, DEFAULT_CASING, DEFAULT_ENV_CASING},
+    dummies,
+    utils::Sp,
+};
+
+use proc_macro2::{Span, TokenStream};
+use proc_macro_error::{abort, abort_call_site};
+use quote::quote;
+use syn::{
+    punctuated::Punctuated, spanned::Spanned, token::Comma, Attribute, Data, DataEnum, DeriveInput,
+    Fields, Ident, Variant,
+};
+
+pub fn derive_arg_enum(input: &DeriveInput) -> TokenStream {
+    let ident = &input.ident;
+
+    dummies::arg_enum(ident);
+
+    match input.data {
+        Data::Enum(ref e) => gen_for_enum(ident, &input.attrs, e),
+        _ => abort_call_site!("`#[derive(ArgEnum)]` only supports enums"),
+    }
+}
+
+pub fn gen_for_enum(name: &Ident, attrs: &[Attribute], e: &DataEnum) -> TokenStream {
+    let attrs = Attrs::from_struct(
+        Span::call_site(),
+        attrs,
+        Name::Derived(name.clone()),
+        Sp::call_site(DEFAULT_CASING),
+        Sp::call_site(DEFAULT_ENV_CASING),
+    );
+
+    let lits = lits(&e.variants, &attrs);
+    let value_variants = gen_value_variants(&lits);
+    let to_possible_value = gen_to_possible_value(&lits);
+
+    quote! {
+        #[allow(dead_code, unreachable_code, unused_variables, unused_braces)]
+        #[allow(
+            clippy::style,
+            clippy::complexity,
+            clippy::pedantic,
+            clippy::restriction,
+            clippy::perf,
+            clippy::deprecated,
+            clippy::nursery,
+            clippy::cargo,
+            clippy::suspicious_else_formatting,
+        )]
+        #[deny(clippy::correctness)]
+        impl clap::ArgEnum for #name {
+            #value_variants
+            #to_possible_value
+        }
+    }
+}
+
+fn lits(
+    variants: &Punctuated<Variant, Comma>,
+    parent_attribute: &Attrs,
+) -> Vec<(TokenStream, Ident)> {
+    variants
+        .iter()
+        .filter_map(|variant| {
+            let attrs = Attrs::from_arg_enum_variant(
+                variant,
+                parent_attribute.casing(),
+                parent_attribute.env_casing(),
+            );
+            if let Kind::Skip(_) = &*attrs.kind() {
+                None
+            } else {
+                if !matches!(variant.fields, Fields::Unit) {
+                    abort!(variant.span(), "`#[derive(ArgEnum)]` only supports non-unit variants, unless they are skipped");
+                }
+                let fields = attrs.field_methods(false);
+                let name = attrs.cased_name();
+                Some((
+                    quote! {
+                        clap::PossibleValue::new(#name)
+                        #fields
+                    },
+                    variant.ident.clone(),
+                ))
+            }
+        })
+        .collect::<Vec<_>>()
+}
+
+fn gen_value_variants(lits: &[(TokenStream, Ident)]) -> TokenStream {
+    let lit = lits.iter().map(|l| &l.1).collect::<Vec<_>>();
+
+    quote! {
+        fn value_variants<'a>() -> &'a [Self]{
+            &[#(Self::#lit),*]
+        }
+    }
+}
+
+fn gen_to_possible_value(lits: &[(TokenStream, Ident)]) -> TokenStream {
+    let (lit, variant): (Vec<TokenStream>, Vec<Ident>) = lits.iter().cloned().unzip();
+
+    quote! {
+        fn to_possible_value<'a>(&self) -> ::std::option::Option<clap::PossibleValue<'a>> {
+            match self {
+                #(Self::#variant => Some(#lit),)*
+                _ => None
+            }
+        }
+    }
+}
diff --git a/third_party/rust/clap_derive/src/derives/args.rs b/third_party/rust/clap_derive/src/derives/args.rs
new file mode 100644
index 0000000000..e1486ea2bd
--- /dev/null
+++ b/third_party/rust/clap_derive/src/derives/args.rs
@@ -0,0 +1,651 @@
+// Copyright 2018 Guillaume Pinot (@TeXitoi) <texitoi@texitoi.eu>,
+// Kevin Knapp (@kbknapp) <kbknapp@gmail.com>, and
+// Ana Hobden (@hoverbear) <operator@hoverbear.org>
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+//
+// This work was derived from Structopt (https://github.com/TeXitoi/structopt)
+// commit#ea76fa1b1b273e65e3b0b1046643715b49bec51f which is licensed under the
+// MIT/Apache 2.0 license.
+
+use crate::{
+    attrs::{Attrs, Kind, Name, ParserKind, DEFAULT_CASING, DEFAULT_ENV_CASING},
+    dummies,
+    utils::{inner_type, sub_type, Sp, Ty},
+};
+
+use proc_macro2::{Ident, Span, TokenStream};
+use proc_macro_error::{abort, abort_call_site};
+use quote::{format_ident, quote, quote_spanned};
+use syn::{
+    punctuated::Punctuated, spanned::Spanned, token::Comma, Attribute, Data, DataStruct,
+    DeriveInput, Field, Fields, Generics, Type,
+};
+
+pub fn derive_args(input: &DeriveInput) -> TokenStream {
+    let ident = &input.ident;
+
+    dummies::args(ident);
+
+    match input.data {
+        Data::Struct(DataStruct {
+            fields: Fields::Named(ref fields),
+            ..
+        }) => gen_for_struct(ident, &input.generics, &fields.named, &input.attrs),
+        Data::Struct(DataStruct {
+            fields: Fields::Unit,
+            ..
+        }) => gen_for_struct(
+            ident,
+            &input.generics,
+            &Punctuated::<Field, Comma>::new(),
+            &input.attrs,
+        ),
+        _ => abort_call_site!("`#[derive(Args)]` only supports non-tuple structs"),
+    }
+}
+
+pub fn gen_for_struct(
+    struct_name: &Ident,
+    generics: &Generics,
+    fields: &Punctuated<Field, Comma>,
+    attrs: &[Attribute],
+) -> TokenStream {
+    let from_arg_matches = gen_from_arg_matches_for_struct(struct_name, generics, fields, attrs);
+
+    let attrs = Attrs::from_struct(
+        Span::call_site(),
+        attrs,
+        Name::Derived(struct_name.clone()),
+        Sp::call_site(DEFAULT_CASING),
+        Sp::call_site(DEFAULT_ENV_CASING),
+    );
+    let app_var = Ident::new("__clap_app", Span::call_site());
+    let augmentation = gen_augment(fields, &app_var, &attrs, false);
+    let augmentation_update = gen_augment(fields, &app_var, &attrs, true);
+
+    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
+
+    quote! {
+        #from_arg_matches
+
+        #[allow(dead_code, unreachable_code, unused_variables, unused_braces)]
+        #[allow(
+            clippy::style,
+            clippy::complexity,
+            clippy::pedantic,
+            clippy::restriction,
+            clippy::perf,
+            clippy::deprecated,
+            clippy::nursery,
+            clippy::cargo,
+            clippy::suspicious_else_formatting,
+        )]
+        #[deny(clippy::correctness)]
+        impl #impl_generics clap::Args for #struct_name #ty_generics #where_clause {
+            fn augment_args<'b>(#app_var: clap::Command<'b>) -> clap::Command<'b> {
+                #augmentation
+            }
+            fn augment_args_for_update<'b>(#app_var: clap::Command<'b>) -> clap::Command<'b> {
+                #augmentation_update
+            }
+        }
+    }
+}
+
+pub fn gen_from_arg_matches_for_struct(
+    struct_name: &Ident,
+    generics: &Generics,
+    fields: &Punctuated<Field, Comma>,
+    attrs: &[Attribute],
+) -> TokenStream {
+    let attrs = Attrs::from_struct(
+        Span::call_site(),
+        attrs,
+        Name::Derived(struct_name.clone()),
+        Sp::call_site(DEFAULT_CASING),
+        Sp::call_site(DEFAULT_ENV_CASING),
+    );
+
+    let constructor = gen_constructor(fields, &attrs);
+    let updater = gen_updater(fields, &attrs, true);
+
+    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
+
+    quote! {
+        #[allow(dead_code, unreachable_code, unused_variables, unused_braces)]
+        #[allow(
+            clippy::style,
+            clippy::complexity,
+            clippy::pedantic,
+            clippy::restriction,
+            clippy::perf,
+            clippy::deprecated,
+            clippy::nursery,
+            clippy::cargo,
+            clippy::suspicious_else_formatting,
+        )]
+        #[deny(clippy::correctness)]
+        impl #impl_generics clap::FromArgMatches for #struct_name #ty_generics #where_clause {
+            fn from_arg_matches(__clap_arg_matches: &clap::ArgMatches) -> ::std::result::Result<Self, clap::Error> {
+                let v = #struct_name #constructor;
+                ::std::result::Result::Ok(v)
+            }
+
+            fn update_from_arg_matches(&mut self, __clap_arg_matches: &clap::ArgMatches) -> ::std::result::Result<(), clap::Error> {
+                #updater
+                ::std::result::Result::Ok(())
+            }
+        }
+    }
+}
+
+/// Generate a block of code to add arguments/subcommands corresponding to
+/// the `fields` to an cmd.
+pub fn gen_augment(
+    fields: &Punctuated<Field, Comma>,
+    app_var: &Ident,
+    parent_attribute: &Attrs,
+    override_required: bool,
+) -> TokenStream {
+    let mut subcmds = fields.iter().filter_map(|field| {
+        let attrs = Attrs::from_field(
+            field,
+            parent_attribute.casing(),
+            parent_attribute.env_casing(),
+        );
+        let kind = attrs.kind();
+        if let Kind::Subcommand(ty) = &*kind {
+            let subcmd_type = match (**ty, sub_type(&field.ty)) {
+                (Ty::Option, Some(sub_type)) => sub_type,
+                _ => &field.ty,
+            };
+            let required = if **ty == Ty::Option {
+                quote!()
+            } else {
+                quote_spanned! { kind.span()=>
+                    #[allow(deprecated)]
+                    let #app_var = #app_var.setting(
+                        clap::AppSettings::SubcommandRequiredElseHelp
+                    );
+                }
+            };
+
+            let span = field.span();
+            let ts = if override_required {
+                quote! {
+                    let #app_var = <#subcmd_type as clap::Subcommand>::augment_subcommands_for_update( #app_var );
+                }
+            } else{
+                quote! {
+                    let #app_var = <#subcmd_type as clap::Subcommand>::augment_subcommands( #app_var );
+                    #required
+                }
+            };
+            Some((span, ts))
+        } else {
+            None
+        }
+    });
+    let subcmd = subcmds.next().map(|(_, ts)| ts);
+    if let Some((span, _)) = subcmds.next() {
+        abort!(
+            span,
+            "multiple subcommand sets are not allowed, that's the second"
+        );
+    }
+
+    let args = fields.iter().filter_map(|field| {
+        let attrs = Attrs::from_field(
+            field,
+            parent_attribute.casing(),
+            parent_attribute.env_casing(),
+        );
+        let kind = attrs.kind();
+        match &*kind {
+            Kind::Subcommand(_)
+            | Kind::Skip(_)
+            | Kind::FromGlobal(_)
+            | Kind::ExternalSubcommand => None,
+            Kind::Flatten => {
+                let ty = &field.ty;
+                let old_heading_var = format_ident!("__clap_old_heading");
+                let next_help_heading = attrs.next_help_heading();
+                let next_display_order = attrs.next_display_order();
+                if override_required {
+                    Some(quote_spanned! { kind.span()=>
+                        let #old_heading_var = #app_var.get_next_help_heading();
+                        let #app_var = #app_var #next_help_heading #next_display_order;
+                        let #app_var = <#ty as clap::Args>::augment_args_for_update(#app_var);
+                        let #app_var = #app_var.next_help_heading(#old_heading_var);
+                    })
+                } else {
+                    Some(quote_spanned! { kind.span()=>
+                        let #old_heading_var = #app_var.get_next_help_heading();
+                        let #app_var = #app_var #next_help_heading #next_display_order;
+                        let #app_var = <#ty as clap::Args>::augment_args(#app_var);
+                        let #app_var = #app_var.next_help_heading(#old_heading_var);
+                    })
+                }
+            }
+            Kind::Arg(ty) => {
+                let convert_type = inner_type(**ty, &field.ty);
+
+                let occurrences = *attrs.parser().kind == ParserKind::FromOccurrences;
+                let flag = *attrs.parser().kind == ParserKind::FromFlag;
+
+                let parser = attrs.parser();
+                let func = &parser.func;
+
+                let validator = match *parser.kind {
+                    _ if attrs.is_enum() => quote!(),
+                    ParserKind::TryFromStr => quote_spanned! { func.span()=>
+                        .validator(|s| {
+                            #func(s)
+                            .map(|_: #convert_type| ())
+                        })
+                    },
+                    ParserKind::TryFromOsStr => quote_spanned! { func.span()=>
+                        .validator_os(|s| #func(s).map(|_: #convert_type| ()))
+                    },
+                    ParserKind::FromStr
+                    | ParserKind::FromOsStr
+                    | ParserKind::FromFlag
+                    | ParserKind::FromOccurrences => quote!(),
+                };
+                let allow_invalid_utf8 = match *parser.kind {
+                    _ if attrs.is_enum() => quote!(),
+                    ParserKind::FromOsStr | ParserKind::TryFromOsStr => {
+                        quote_spanned! { func.span()=>
+                            .allow_invalid_utf8(true)
+                        }
+                    }
+                    ParserKind::FromStr
+                    | ParserKind::TryFromStr
+                    | ParserKind::FromFlag
+                    | ParserKind::FromOccurrences => quote!(),
+                };
+
+                let value_name = attrs.value_name();
+                let possible_values = if attrs.is_enum() {
+                    gen_arg_enum_possible_values(convert_type)
+                } else {
+                    quote!()
+                };
+
+                let modifier = match **ty {
+                    Ty::Bool => quote!(),
+
+                    Ty::Option => {
+                        quote_spanned! { ty.span()=>
+                            .takes_value(true)
+                            .value_name(#value_name)
+                            #possible_values
+                            #validator
+                            #allow_invalid_utf8
+                        }
+                    }
+
+                    Ty::OptionOption => quote_spanned! { ty.span()=>
+                        .takes_value(true)
+                        .value_name(#value_name)
+                        .min_values(0)
+                        .max_values(1)
+                        .multiple_values(false)
+                        #possible_values
+                        #validator
+                        #allow_invalid_utf8
+                    },
+
+                    Ty::OptionVec => quote_spanned! { ty.span()=>
+                        .takes_value(true)
+                        .value_name(#value_name)
+                        .multiple_occurrences(true)
+                        #possible_values
+                        #validator
+                        #allow_invalid_utf8
+                    },
+
+                    Ty::Vec => {
+                        quote_spanned! { ty.span()=>
+                            .takes_value(true)
+                            .value_name(#value_name)
+                            .multiple_occurrences(true)
+                            #possible_values
+                            #validator
+                            #allow_invalid_utf8
+                        }
+                    }
+
+                    Ty::Other if occurrences => quote_spanned! { ty.span()=>
+                        .multiple_occurrences(true)
+                    },
+
+                    Ty::Other if flag => quote_spanned! { ty.span()=>
+                        .takes_value(false)
+                    },
+
+                    Ty::Other => {
+                        let required = attrs.find_default_method().is_none() && !override_required;
+                        quote_spanned! { ty.span()=>
+                            .takes_value(true)
+                            .value_name(#value_name)
+                            .required(#required)
+                            #possible_values
+                            #validator
+                            #allow_invalid_utf8
+                        }
+                    }
+                };
+
+                let id = attrs.id();
+                let methods = attrs.field_methods(true);
+
+                Some(quote_spanned! { field.span()=>
+                    let #app_var = #app_var.arg(
+                        clap::Arg::new(#id)
+                            #modifier
+                            #methods
+                    );
+                })
+            }
+        }
+    });
+
+    let initial_app_methods = parent_attribute.initial_top_level_methods();
+    let final_app_methods = parent_attribute.final_top_level_methods();
+    quote! {{
+        let #app_var = #app_var #initial_app_methods;
+        #( #args )*
+        #subcmd
+        #app_var #final_app_methods
+    }}
+}
+
+fn gen_arg_enum_possible_values(ty: &Type) -> TokenStream {
+    quote_spanned! { ty.span()=>
+        .possible_values(<#ty as clap::ArgEnum>::value_variants().iter().filter_map(clap::ArgEnum::to_possible_value))
+    }
+}
+
+pub fn gen_constructor(fields: &Punctuated<Field, Comma>, parent_attribute: &Attrs) -> TokenStream {
+    let fields = fields.iter().map(|field| {
+        let attrs = Attrs::from_field(
+            field,
+            parent_attribute.casing(),
+            parent_attribute.env_casing(),
+        );
+        let field_name = field.ident.as_ref().unwrap();
+        let kind = attrs.kind();
+        let arg_matches = format_ident!("__clap_arg_matches");
+        match &*kind {
+            Kind::ExternalSubcommand => {
+                abort! { kind.span(),
+                    "`external_subcommand` can be used only on enum variants"
+                }
+            }
+            Kind::Subcommand(ty) => {
+                let subcmd_type = match (**ty, sub_type(&field.ty)) {
+                    (Ty::Option, Some(sub_type)) => sub_type,
+                    _ => &field.ty,
+                };
+                match **ty {
+                    Ty::Option => {
+                        quote_spanned! { kind.span()=>
+                            #field_name: {
+                                if #arg_matches.subcommand_name().map(<#subcmd_type as clap::Subcommand>::has_subcommand).unwrap_or(false) {
+                                    Some(<#subcmd_type as clap::FromArgMatches>::from_arg_matches(#arg_matches)?)
+                                } else {
+                                    None
+                                }
+                            }
+                        }
+                    },
+                    _ => {
+                        quote_spanned! { kind.span()=>
+                            #field_name: {
+                                <#subcmd_type as clap::FromArgMatches>::from_arg_matches(#arg_matches)?
+                            }
+                        }
+                    },
+                }
+            }
+
+            Kind::Flatten => quote_spanned! { kind.span()=>
+                #field_name: clap::FromArgMatches::from_arg_matches(#arg_matches)?
+            },
+
+            Kind::Skip(val) => match val {
+                None => quote_spanned!(kind.span()=> #field_name: Default::default()),
+                Some(val) => quote_spanned!(kind.span()=> #field_name: (#val).into()),
+            },
+
+            Kind::Arg(ty) | Kind::FromGlobal(ty) => {
+                gen_parsers(&attrs, ty, field_name, field, None)
+            }
+        }
+    });
+
+    quote! {{
+        #( #fields ),*
+    }}
+}
+
+pub fn gen_updater(
+    fields: &Punctuated<Field, Comma>,
+    parent_attribute: &Attrs,
+    use_self: bool,
+) -> TokenStream {
+    let fields = fields.iter().map(|field| {
+        let attrs = Attrs::from_field(
+            field,
+            parent_attribute.casing(),
+            parent_attribute.env_casing(),
+        );
+        let field_name = field.ident.as_ref().unwrap();
+        let kind = attrs.kind();
+
+        let access = if use_self {
+            quote! {
+                #[allow(non_snake_case)]
+                let #field_name = &mut self.#field_name;
+            }
+        } else {
+            quote!()
+        };
+        let arg_matches = format_ident!("__clap_arg_matches");
+
+        match &*kind {
+            Kind::ExternalSubcommand => {
+                abort! { kind.span(),
+                    "`external_subcommand` can be used only on enum variants"
+                }
+            }
+            Kind::Subcommand(ty) => {
+                let subcmd_type = match (**ty, sub_type(&field.ty)) {
+                    (Ty::Option, Some(sub_type)) => sub_type,
+                    _ => &field.ty,
+                };
+
+                let updater = quote_spanned! { ty.span()=>
+                    <#subcmd_type as clap::FromArgMatches>::update_from_arg_matches(#field_name, #arg_matches)?;
+                };
+
+                let updater = match **ty {
+                    Ty::Option => quote_spanned! { kind.span()=>
+                        if let Some(#field_name) = #field_name.as_mut() {
+                            #updater
+                        } else {
+                            *#field_name = Some(<#subcmd_type as clap::FromArgMatches>::from_arg_matches(
+                                #arg_matches
+                            )?);
+                        }
+                    },
+                    _ => quote_spanned! { kind.span()=>
+                        #updater
+                    },
+                };
+
+                quote_spanned! { kind.span()=>
+                    {
+                        #access
+                        #updater
+                    }
+                }
+            }
+
+            Kind::Flatten => quote_spanned! { kind.span()=> {
+                    #access
+                    clap::FromArgMatches::update_from_arg_matches(#field_name, #arg_matches)?;
+                }
+            },
+
+            Kind::Skip(_) => quote!(),
+
+            Kind::Arg(ty) | Kind::FromGlobal(ty) => gen_parsers(&attrs, ty, field_name, field, Some(&access)),
+        }
+    });
+
+    quote! {
+        #( #fields )*
+    }
+}
+
+fn gen_parsers(
+    attrs: &Attrs,
+    ty: &Sp<Ty>,
+    field_name: &Ident,
+    field: &Field,
+    update: Option<&TokenStream>,
+) -> TokenStream {
+    use self::ParserKind::*;
+
+    let parser = attrs.parser();
+    let func = &parser.func;
+    let span = parser.kind.span();
+    let convert_type = inner_type(**ty, &field.ty);
+    let id = attrs.id();
+    let (value_of, values_of, mut parse) = match *parser.kind {
+        FromStr => (
+            quote_spanned!(span=> value_of),
+            quote_spanned!(span=> values_of),
+            quote_spanned!(func.span()=> |s| ::std::result::Result::Ok::<_, clap::Error>(#func(s))),
+        ),
+        TryFromStr => (
+            quote_spanned!(span=> value_of),
+            quote_spanned!(span=> values_of),
+            quote_spanned!(func.span()=> |s| #func(s).map_err(|err| clap::Error::raw(clap::ErrorKind::ValueValidation, format!("Invalid value for {}: {}", #id, err)))),
+        ),
+        FromOsStr => (
+            quote_spanned!(span=> value_of_os),
+            quote_spanned!(span=> values_of_os),
+            quote_spanned!(func.span()=> |s| ::std::result::Result::Ok::<_, clap::Error>(#func(s))),
+        ),
+        TryFromOsStr => (
+            quote_spanned!(span=> value_of_os),
+            quote_spanned!(span=> values_of_os),
+            quote_spanned!(func.span()=> |s| #func(s).map_err(|err| clap::Error::raw(clap::ErrorKind::ValueValidation, format!("Invalid value for {}: {}", #id, err)))),
+        ),
+        FromOccurrences => (
+            quote_spanned!(span=> occurrences_of),
+            quote!(),
+            func.clone(),
+        ),
+        FromFlag => (quote!(), quote!(), func.clone()),
+    };
+    if attrs.is_enum() {
+        let ci = attrs.ignore_case();
+
+        parse = quote_spanned! { convert_type.span()=>
+            |s| <#convert_type as clap::ArgEnum>::from_str(s, #ci).map_err(|err| clap::Error::raw(clap::ErrorKind::ValueValidation, format!("Invalid value for {}: {}", #id, err)))
+        }
+    }
+
+    let flag = *attrs.parser().kind == ParserKind::FromFlag;
+    let occurrences = *attrs.parser().kind == ParserKind::FromOccurrences;
+    // Give this identifier the same hygiene
+    // as the `arg_matches` parameter definition. This
+    // allows us to refer to `arg_matches` within a `quote_spanned` block
+    let arg_matches = format_ident!("__clap_arg_matches");
+
+    let field_value = match **ty {
+        Ty::Bool => {
+            if update.is_some() {
+                quote_spanned! { ty.span()=>
+                    *#field_name || #arg_matches.is_present(#id)
+                }
+            } else {
+                quote_spanned! { ty.span()=>
+                    #arg_matches.is_present(#id)
+                }
+            }
+        }
+
+        Ty::Option => {
+            quote_spanned! { ty.span()=>
+                #arg_matches.#value_of(#id)
+                    .map(#parse)
+                    .transpose()?
+            }
+        }
+
+        Ty::OptionOption => quote_spanned! { ty.span()=>
+            if #arg_matches.is_present(#id) {
+                Some(#arg_matches.#value_of(#id).map(#parse).transpose()?)
+            } else {
+                None
+            }
+        },
+
+        Ty::OptionVec => quote_spanned! { ty.span()=>
+            if #arg_matches.is_present(#id) {
+                Some(#arg_matches.#values_of(#id)
+                    .map(|v| v.map::<::std::result::Result<#convert_type, clap::Error>, _>(#parse).collect::<::std::result::Result<Vec<_>, clap::Error>>())
+                    .transpose()?
+                    .unwrap_or_else(Vec::new))
+            } else {
+                None
+            }
+        },
+
+        Ty::Vec => {
+            quote_spanned! { ty.span()=>
+                #arg_matches.#values_of(#id)
+                    .map(|v| v.map::<::std::result::Result<#convert_type, clap::Error>, _>(#parse).collect::<::std::result::Result<Vec<_>, clap::Error>>())
+                    .transpose()?
+                    .unwrap_or_else(Vec::new)
+            }
+        }
+
+        Ty::Other if occurrences => quote_spanned! { ty.span()=>
+            #parse(#arg_matches.#value_of(#id))
+        },
+
+        Ty::Other if flag => quote_spanned! { ty.span()=>
+            #parse(#arg_matches.is_present(#id))
+        },
+
+        Ty::Other => {
+            quote_spanned! { ty.span()=>
+                #arg_matches.#value_of(#id)
+                    .ok_or_else(|| clap::Error::raw(clap::ErrorKind::MissingRequiredArgument, format!("The following required argument was not provided: {}", #id)))
+                    .and_then(#parse)?
+            }
+        }
+    };
+
+    if let Some(access) = update {
+        quote_spanned! { field.span()=>
+            if #arg_matches.is_present(#id) {
+                #access
+                *#field_name = #field_value
+            }
+        }
+    } else {
+        quote_spanned!(field.span()=> #field_name: #field_value )
+    }
+}
diff --git a/third_party/rust/clap_derive/src/derives/into_app.rs b/third_party/rust/clap_derive/src/derives/into_app.rs
new file mode 100644
index 0000000000..3197357534
--- /dev/null
+++ b/third_party/rust/clap_derive/src/derives/into_app.rs
@@ -0,0 +1,119 @@
+// Copyright 2018 Guillaume Pinot (@TeXitoi) <texitoi@texitoi.eu>,
+// Kevin Knapp (@kbknapp) <kbknapp@gmail.com>, and
+// Ana Hobden (@hoverbear) <operator@hoverbear.org>
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+//
+// This work was derived from Structopt (https://github.com/TeXitoi/structopt)
+// commit#ea76fa1b1b273e65e3b0b1046643715b49bec51f which is licensed under the
+// MIT/Apache 2.0 license.
+
+use std::env;
+
+use proc_macro2::{Span, TokenStream};
+use quote::quote;
+use syn::{Attribute, Generics, Ident};
+
+use crate::{
+    attrs::{Attrs, Name, DEFAULT_CASING, DEFAULT_ENV_CASING},
+    utils::Sp,
+};
+
+pub fn gen_for_struct(
+    struct_name: &Ident,
+    generics: &Generics,
+    attrs: &[Attribute],
+) -> TokenStream {
+    let app_name = env::var("CARGO_PKG_NAME").ok().unwrap_or_default();
+
+    let attrs = Attrs::from_struct(
+        Span::call_site(),
+        attrs,
+        Name::Assigned(quote!(#app_name)),
+        Sp::call_site(DEFAULT_CASING),
+        Sp::call_site(DEFAULT_ENV_CASING),
+    );
+    let name = attrs.cased_name();
+    let app_var = Ident::new("__clap_app", Span::call_site());
+
+    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
+
+    let tokens = quote! {
+        #[allow(dead_code, unreachable_code, unused_variables, unused_braces)]
+        #[allow(
+            clippy::style,
+            clippy::complexity,
+            clippy::pedantic,
+            clippy::restriction,
+            clippy::perf,
+            clippy::deprecated,
+            clippy::nursery,
+            clippy::cargo,
+            clippy::suspicious_else_formatting,
+        )]
+        #[deny(clippy::correctness)]
+        #[allow(deprecated)]
+        impl #impl_generics clap::CommandFactory for #struct_name #ty_generics #where_clause {
+            fn into_app<'b>() -> clap::Command<'b> {
+                let #app_var = clap::Command::new(#name);
+                <Self as clap::Args>::augment_args(#app_var)
+            }
+
+            fn into_app_for_update<'b>() -> clap::Command<'b> {
+                let #app_var = clap::Command::new(#name);
+                <Self as clap::Args>::augment_args_for_update(#app_var)
+            }
+        }
+    };
+
+    tokens
+}
+
+pub fn gen_for_enum(enum_name: &Ident, generics: &Generics, attrs: &[Attribute]) -> TokenStream {
+    let app_name = env::var("CARGO_PKG_NAME").ok().unwrap_or_default();
+
+    let attrs = Attrs::from_struct(
+        Span::call_site(),
+        attrs,
+        Name::Assigned(quote!(#app_name)),
+        Sp::call_site(DEFAULT_CASING),
+        Sp::call_site(DEFAULT_ENV_CASING),
+    );
+    let name = attrs.cased_name();
+    let app_var = Ident::new("__clap_app", Span::call_site());
+
+    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
+
+    quote! {
+        #[allow(dead_code, unreachable_code, unused_variables, unused_braces)]
+        #[allow(
+            clippy::style,
+            clippy::complexity,
+            clippy::pedantic,
+            clippy::restriction,
+            clippy::perf,
+            clippy::deprecated,
+            clippy::nursery,
+            clippy::cargo,
+            clippy::suspicious_else_formatting,
+        )]
+        #[deny(clippy::correctness)]
+        impl #impl_generics clap::CommandFactory for #enum_name #ty_generics #where_clause {
+            fn into_app<'b>() -> clap::Command<'b> {
+                #[allow(deprecated)]
+                let #app_var = clap::Command::new(#name)
+                    .setting(clap::AppSettings::SubcommandRequiredElseHelp);
+                <Self as clap::Subcommand>::augment_subcommands(#app_var)
+            }
+
+            fn into_app_for_update<'b>() -> clap::Command<'b> {
+                let #app_var = clap::Command::new(#name);
+                <Self as clap::Subcommand>::augment_subcommands_for_update(#app_var)
+            }
+        }
+    }
+}
diff --git a/third_party/rust/clap_derive/src/derives/mod.rs b/third_party/rust/clap_derive/src/derives/mod.rs
new file mode 100644
index 0000000000..ee0cce56e7
--- /dev/null
+++ b/third_party/rust/clap_derive/src/derives/mod.rs
@@ -0,0 +1,23 @@
+// Copyright 2018 Guillaume Pinot (@TeXitoi) <texitoi@texitoi.eu>,
+// Kevin Knapp (@kbknapp) <kbknapp@gmail.com>, and
+// Ana Hobden (@hoverbear) <operator@hoverbear.org>
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+//
+// This work was derived from Structopt (https://github.com/TeXitoi/structopt)
+// commit#ea76fa1b1b273e65e3b0b1046643715b49bec51f which is licensed under the
+// MIT/Apache 2.0 license.
+mod arg_enum;
+mod args;
+mod into_app;
+mod parser;
+mod subcommand;
+
+pub use self::parser::derive_parser;
+pub use arg_enum::derive_arg_enum;
+pub use args::derive_args;
+pub use subcommand::derive_subcommand;
diff --git a/third_party/rust/clap_derive/src/derives/parser.rs b/third_party/rust/clap_derive/src/derives/parser.rs
new file mode 100644
index 0000000000..621430f310
--- /dev/null
+++ b/third_party/rust/clap_derive/src/derives/parser.rs
@@ -0,0 +1,95 @@
+// Copyright 2018 Guillaume Pinot (@TeXitoi) <texitoi@texitoi.eu>,
+// Kevin Knapp (@kbknapp) <kbknapp@gmail.com>, and
+// Ana Hobden (@hoverbear) <operator@hoverbear.org>
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+//
+// This work was derived from Structopt (https://github.com/TeXitoi/structopt)
+// commit#ea76fa1b1b273e65e3b0b1046643715b49bec51f which is licensed under the
+// MIT/Apache 2.0 license.
+
+use crate::{
+    derives::{args, into_app, subcommand},
+    dummies,
+};
+
+use proc_macro2::TokenStream;
+use proc_macro_error::abort_call_site;
+use quote::quote;
+use syn::{
+    self, punctuated::Punctuated, token::Comma, Attribute, Data, DataEnum, DataStruct, DeriveInput,
+    Field, Fields, Generics, Ident,
+};
+
+pub fn derive_parser(input: &DeriveInput) -> TokenStream {
+    let ident = &input.ident;
+
+    match input.data {
+        Data::Struct(DataStruct {
+            fields: Fields::Named(ref fields),
+            ..
+        }) => {
+            dummies::parser_struct(ident);
+            gen_for_struct(ident, &input.generics, &fields.named, &input.attrs)
+        }
+        Data::Struct(DataStruct {
+            fields: Fields::Unit,
+            ..
+        }) => {
+            dummies::parser_struct(ident);
+            gen_for_struct(
+                ident,
+                &input.generics,
+                &Punctuated::<Field, Comma>::new(),
+                &input.attrs,
+            )
+        }
+        Data::Enum(ref e) => {
+            dummies::parser_enum(ident);
+            gen_for_enum(ident, &input.generics, &input.attrs, e)
+        }
+        _ => abort_call_site!("`#[derive(Parser)]` only supports non-tuple structs and enums"),
+    }
+}
+
+fn gen_for_struct(
+    name: &Ident,
+    generics: &Generics,
+    fields: &Punctuated<Field, Comma>,
+    attrs: &[Attribute],
+) -> TokenStream {
+    let into_app = into_app::gen_for_struct(name, generics, attrs);
+    let args = args::gen_for_struct(name, generics, fields, attrs);
+
+    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
+
+    quote! {
+        impl #impl_generics clap::Parser for #name #ty_generics #where_clause {}
+
+        #into_app
+        #args
+    }
+}
+
+fn gen_for_enum(
+    name: &Ident,
+    generics: &Generics,
+    attrs: &[Attribute],
+    e: &DataEnum,
+) -> TokenStream {
+    let into_app = into_app::gen_for_enum(name, generics, attrs);
+    let subcommand = subcommand::gen_for_enum(name, generics, attrs, e);
+
+    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
+
+    quote! {
+        impl #impl_generics clap::Parser for #name #ty_generics #where_clause {}
+
+        #into_app
+        #subcommand
+    }
+}
diff --git a/third_party/rust/clap_derive/src/derives/subcommand.rs b/third_party/rust/clap_derive/src/derives/subcommand.rs
new file mode 100644
index 0000000000..7d12347985
--- /dev/null
+++ b/third_party/rust/clap_derive/src/derives/subcommand.rs
@@ -0,0 +1,666 @@
+// Copyright 2018 Guillaume Pinot (@TeXitoi) <texitoi@texitoi.eu>,
+// Kevin Knapp (@kbknapp) <kbknapp@gmail.com>, and
+// Ana Hobden (@hoverbear) <operator@hoverbear.org>
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+//
+// This work was derived from Structopt (https://github.com/TeXitoi/structopt)
+// commit#ea76fa1b1b273e65e3b0b1046643715b49bec51f which is licensed under the
+// MIT/Apache 2.0 license.
+use crate::{
+    attrs::{Attrs, Kind, Name, DEFAULT_CASING, DEFAULT_ENV_CASING},
+    derives::args,
+    dummies,
+    utils::{is_simple_ty, subty_if_name, Sp},
+};
+
+use proc_macro2::{Ident, Span, TokenStream};
+use proc_macro_error::{abort, abort_call_site};
+use quote::{format_ident, quote, quote_spanned};
+use syn::{
+    punctuated::Punctuated, spanned::Spanned, Attribute, Data, DataEnum, DeriveInput,
+    FieldsUnnamed, Generics, Token, Variant,
+};
+
+pub fn derive_subcommand(input: &DeriveInput) -> TokenStream {
+    let ident = &input.ident;
+
+    dummies::subcommand(ident);
+
+    match input.data {
+        Data::Enum(ref e) => gen_for_enum(ident, &input.generics, &input.attrs, e),
+        _ => abort_call_site!("`#[derive(Subcommand)]` only supports enums"),
+    }
+}
+
+pub fn gen_for_enum(
+    enum_name: &Ident,
+    generics: &Generics,
+    attrs: &[Attribute],
+    e: &DataEnum,
+) -> TokenStream {
+    let from_arg_matches = gen_from_arg_matches_for_enum(enum_name, generics, attrs, e);
+
+    let attrs = Attrs::from_struct(
+        Span::call_site(),
+        attrs,
+        Name::Derived(enum_name.clone()),
+        Sp::call_site(DEFAULT_CASING),
+        Sp::call_site(DEFAULT_ENV_CASING),
+    );
+    let augmentation = gen_augment(&e.variants, &attrs, false);
+    let augmentation_update = gen_augment(&e.variants, &attrs, true);
+    let has_subcommand = gen_has_subcommand(&e.variants, &attrs);
+
+    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
+
+    quote! {
+        #from_arg_matches
+
+        #[allow(dead_code, unreachable_code, unused_variables, unused_braces)]
+        #[allow(
+            clippy::style,
+            clippy::complexity,
+            clippy::pedantic,
+            clippy::restriction,
+            clippy::perf,
+            clippy::deprecated,
+            clippy::nursery,
+            clippy::cargo,
+            clippy::suspicious_else_formatting,
+        )]
+        #[deny(clippy::correctness)]
+        impl #impl_generics clap::Subcommand for #enum_name #ty_generics #where_clause {
+            fn augment_subcommands <'b>(__clap_app: clap::Command<'b>) -> clap::Command<'b> {
+                #augmentation
+            }
+            fn augment_subcommands_for_update <'b>(__clap_app: clap::Command<'b>) -> clap::Command<'b> {
+                #augmentation_update
+            }
+            fn has_subcommand(__clap_name: &str) -> bool {
+                #has_subcommand
+            }
+        }
+    }
+}
+
+fn gen_from_arg_matches_for_enum(
+    name: &Ident,
+    generics: &Generics,
+    attrs: &[Attribute],
+    e: &DataEnum,
+) -> TokenStream {
+    let attrs = Attrs::from_struct(
+        Span::call_site(),
+        attrs,
+        Name::Derived(name.clone()),
+        Sp::call_site(DEFAULT_CASING),
+        Sp::call_site(DEFAULT_ENV_CASING),
+    );
+
+    let from_arg_matches = gen_from_arg_matches(name, &e.variants, &attrs);
+    let update_from_arg_matches = gen_update_from_arg_matches(name, &e.variants, &attrs);
+
+    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
+
+    quote! {
+        #[allow(dead_code, unreachable_code, unused_variables, unused_braces)]
+        #[allow(
+            clippy::style,
+            clippy::complexity,
+            clippy::pedantic,
+            clippy::restriction,
+            clippy::perf,
+            clippy::deprecated,
+            clippy::nursery,
+            clippy::cargo,
+            clippy::suspicious_else_formatting,
+        )]
+        #[deny(clippy::correctness)]
+        impl #impl_generics clap::FromArgMatches for #name #ty_generics #where_clause {
+            #from_arg_matches
+            #update_from_arg_matches
+        }
+    }
+}
+
+fn gen_augment(
+    variants: &Punctuated<Variant, Token![,]>,
+    parent_attribute: &Attrs,
+    override_required: bool,
+) -> TokenStream {
+    use syn::Fields::*;
+
+    let app_var = Ident::new("__clap_app", Span::call_site());
+
+    let subcommands: Vec<_> = variants
+        .iter()
+        .filter_map(|variant| {
+            let attrs = Attrs::from_variant(
+                variant,
+                parent_attribute.casing(),
+                parent_attribute.env_casing(),
+            );
+            let kind = attrs.kind();
+
+            match &*kind {
+                Kind::Skip(_) => None,
+
+                Kind::ExternalSubcommand => {
+                    let ty = match variant.fields {
+                        Unnamed(ref fields) if fields.unnamed.len() == 1 => &fields.unnamed[0].ty,
+
+                        _ => abort!(
+                            variant,
+                            "The enum variant marked with `external_subcommand` must be \
+                             a single-typed tuple, and the type must be either `Vec<String>` \
+                             or `Vec<OsString>`."
+                        ),
+                    };
+                    let subcommand = match subty_if_name(ty, "Vec") {
+                        Some(subty) => {
+                            if is_simple_ty(subty, "OsString") {
+                                quote_spanned! { kind.span()=>
+                                    let #app_var = #app_var.allow_external_subcommands(true).allow_invalid_utf8_for_external_subcommands(true);
+                                }
+                            } else {
+                                quote_spanned! { kind.span()=>
+                                    let #app_var = #app_var.allow_external_subcommands(true);
+                                }
+                            }
+                        }
+
+                        None => abort!(
+                            ty.span(),
+                            "The type must be `Vec<_>` \
+                             to be used with `external_subcommand`."
+                        ),
+                    };
+                    Some(subcommand)
+                }
+
+                Kind::Flatten => match variant.fields {
+                    Unnamed(FieldsUnnamed { ref unnamed, .. }) if unnamed.len() == 1 => {
+                        let ty = &unnamed[0];
+                        let old_heading_var = format_ident!("__clap_old_heading");
+                        let next_help_heading = attrs.next_help_heading();
+                        let next_display_order = attrs.next_display_order();
+                        let subcommand = if override_required {
+                            quote! {
+                                let #old_heading_var = #app_var.get_next_help_heading();
+                                let #app_var = #app_var #next_help_heading #next_display_order;
+                                let #app_var = <#ty as clap::Subcommand>::augment_subcommands_for_update(#app_var);
+                                let #app_var = #app_var.next_help_heading(#old_heading_var);
+                            }
+                        } else {
+                            quote! {
+                                let #old_heading_var = #app_var.get_next_help_heading();
+                                let #app_var = #app_var #next_help_heading #next_display_order;
+                                let #app_var = <#ty as clap::Subcommand>::augment_subcommands(#app_var);
+                                let #app_var = #app_var.next_help_heading(#old_heading_var);
+                            }
+                        };
+                        Some(subcommand)
+                    }
+                    _ => abort!(
+                        variant,
+                        "`flatten` is usable only with single-typed tuple variants"
+                    ),
+                },
+
+                Kind::Subcommand(_) => {
+                    let subcommand_var = Ident::new("__clap_subcommand", Span::call_site());
+                    let arg_block = match variant.fields {
+                        Named(_) => {
+                            abort!(variant, "non single-typed tuple enums are not supported")
+                        }
+                        Unit => quote!( #subcommand_var ),
+                        Unnamed(FieldsUnnamed { ref unnamed, .. }) if unnamed.len() == 1 => {
+                            let ty = &unnamed[0];
+                            if override_required {
+                                quote_spanned! { ty.span()=>
+                                    {
+                                        <#ty as clap::Subcommand>::augment_subcommands_for_update(#subcommand_var)
+                                    }
+                                }
+                            } else {
+                                quote_spanned! { ty.span()=>
+                                    {
+                                        <#ty as clap::Subcommand>::augment_subcommands(#subcommand_var)
+                                    }
+                                }
+                            }
+                        }
+                        Unnamed(..) => {
+                            abort!(variant, "non single-typed tuple enums are not supported")
+                        }
+                    };
+
+                    let name = attrs.cased_name();
+                    let initial_app_methods = attrs.initial_top_level_methods();
+                    let final_from_attrs = attrs.final_top_level_methods();
+                    let subcommand = quote! {
+                        let #app_var = #app_var.subcommand({
+                            let #subcommand_var = clap::Command::new(#name);
+                            let #subcommand_var = #subcommand_var #initial_app_methods;
+                            let #subcommand_var = #arg_block;
+                            #[allow(deprecated)]
+                            let #subcommand_var = #subcommand_var.setting(clap::AppSettings::SubcommandRequiredElseHelp);
+                            #subcommand_var #final_from_attrs
+                        });
+                    };
+                    Some(subcommand)
+                }
+
+                _ => {
+                    let subcommand_var = Ident::new("__clap_subcommand", Span::call_site());
+                    let sub_augment = match variant.fields {
+                        Named(ref fields) => {
+                            // Defer to `gen_augment` for adding cmd methods
+                            args::gen_augment(&fields.named, &subcommand_var, &attrs, override_required)
+                        }
+                        Unit => {
+                            let arg_block = quote!( #subcommand_var );
+                            let initial_app_methods = attrs.initial_top_level_methods();
+                            let final_from_attrs = attrs.final_top_level_methods();
+                            quote! {
+                                let #subcommand_var = #subcommand_var #initial_app_methods;
+                                let #subcommand_var = #arg_block;
+                                #subcommand_var #final_from_attrs
+                            }
+                        },
+                        Unnamed(FieldsUnnamed { ref unnamed, .. }) if unnamed.len() == 1 => {
+                            let ty = &unnamed[0];
+                            let arg_block = if override_required {
+                                quote_spanned! { ty.span()=>
+                                    {
+                                        <#ty as clap::Args>::augment_args_for_update(#subcommand_var)
+                                    }
+                                }
+                            } else {
+                                quote_spanned! { ty.span()=>
+                                    {
+                                        <#ty as clap::Args>::augment_args(#subcommand_var)
+                                    }
+                                }
+                            };
+                            let initial_app_methods = attrs.initial_top_level_methods();
+                            let final_from_attrs = attrs.final_top_level_methods();
+                            quote! {
+                                let #subcommand_var = #subcommand_var #initial_app_methods;
+                                let #subcommand_var = #arg_block;
+                                #subcommand_var #final_from_attrs
+                            }
+                        }
+                        Unnamed(..) => {
+                            abort!(variant, "non single-typed tuple enums are not supported")
+                        }
+                    };
+
+                    let name = attrs.cased_name();
+                    let subcommand = quote! {
+                        let #app_var = #app_var.subcommand({
+                            let #subcommand_var = clap::Command::new(#name);
+                            #sub_augment
+                        });
+                    };
+                    Some(subcommand)
+                }
+            }
+        })
+        .collect();
+
+    let initial_app_methods = parent_attribute.initial_top_level_methods();
+    let final_app_methods = parent_attribute.final_top_level_methods();
+    quote! {
+            let #app_var = #app_var #initial_app_methods;
+            #( #subcommands )*;
+            #app_var #final_app_methods
+    }
+}
+
+fn gen_has_subcommand(
+    variants: &Punctuated<Variant, Token![,]>,
+    parent_attribute: &Attrs,
+) -> TokenStream {
+    use syn::Fields::*;
+
+    let mut ext_subcmd = false;
+
+    let (flatten_variants, variants): (Vec<_>, Vec<_>) = variants
+        .iter()
+        .filter_map(|variant| {
+            let attrs = Attrs::from_variant(
+                variant,
+                parent_attribute.casing(),
+                parent_attribute.env_casing(),
+            );
+
+            if let Kind::ExternalSubcommand = &*attrs.kind() {
+                ext_subcmd = true;
+                None
+            } else {
+                Some((variant, attrs))
+            }
+        })
+        .partition(|(_, attrs)| {
+            let kind = attrs.kind();
+            matches!(&*kind, Kind::Flatten)
+        });
+
+    let subcommands = variants.iter().map(|(_variant, attrs)| {
+        let sub_name = attrs.cased_name();
+        quote! {
+            if #sub_name == __clap_name {
+                return true
+            }
+        }
+    });
+    let child_subcommands = flatten_variants
+        .iter()
+        .map(|(variant, _attrs)| match variant.fields {
+            Unnamed(ref fields) if fields.unnamed.len() == 1 => {
+                let ty = &fields.unnamed[0];
+                quote! {
+                    if <#ty as clap::Subcommand>::has_subcommand(__clap_name) {
+                        return true;
+                    }
+                }
+            }
+            _ => abort!(
+                variant,
+                "`flatten` is usable only with single-typed tuple variants"
+            ),
+        });
+
+    if ext_subcmd {
+        quote! { true }
+    } else {
+        quote! {
+            #( #subcommands )*
+
+            #( #child_subcommands )else*
+
+            false
+        }
+    }
+}
+
+fn gen_from_arg_matches(
+    name: &Ident,
+    variants: &Punctuated<Variant, Token![,]>,
+    parent_attribute: &Attrs,
+) -> TokenStream {
+    use syn::Fields::*;
+
+    let mut ext_subcmd = None;
+
+    let subcommand_name_var = format_ident!("__clap_name");
+    let sub_arg_matches_var = format_ident!("__clap_sub_arg_matches");
+    let (flatten_variants, variants): (Vec<_>, Vec<_>) = variants
+        .iter()
+        .filter_map(|variant| {
+            let attrs = Attrs::from_variant(
+                variant,
+                parent_attribute.casing(),
+                parent_attribute.env_casing(),
+            );
+
+            if let Kind::ExternalSubcommand = &*attrs.kind() {
+                if ext_subcmd.is_some() {
+                    abort!(
+                        attrs.kind().span(),
+                        "Only one variant can be marked with `external_subcommand`, \
+                         this is the second"
+                    );
+                }
+
+                let ty = match variant.fields {
+                    Unnamed(ref fields) if fields.unnamed.len() == 1 => &fields.unnamed[0].ty,
+
+                    _ => abort!(
+                        variant,
+                        "The enum variant marked with `external_subcommand` must be \
+                         a single-typed tuple, and the type must be either `Vec<String>` \
+                         or `Vec<OsString>`."
+                    ),
+                };
+
+                let (span, str_ty, values_of) = match subty_if_name(ty, "Vec") {
+                    Some(subty) => {
+                        if is_simple_ty(subty, "String") {
+                            (
+                                subty.span(),
+                                quote!(::std::string::String),
+                                quote!(values_of),
+                            )
+                        } else if is_simple_ty(subty, "OsString") {
+                            (
+                                subty.span(),
+                                quote!(::std::ffi::OsString),
+                                quote!(values_of_os),
+                            )
+                        } else {
+                            abort!(
+                                ty.span(),
+                                "The type must be either `Vec<String>` or `Vec<OsString>` \
+                                 to be used with `external_subcommand`."
+                            );
+                        }
+                    }
+
+                    None => abort!(
+                        ty.span(),
+                        "The type must be either `Vec<String>` or `Vec<OsString>` \
+                         to be used with `external_subcommand`."
+                    ),
+                };
+
+                ext_subcmd = Some((span, &variant.ident, str_ty, values_of));
+                None
+            } else {
+                Some((variant, attrs))
+            }
+        })
+        .partition(|(_, attrs)| {
+            let kind = attrs.kind();
+            matches!(&*kind, Kind::Flatten)
+        });
+
+    let subcommands = variants.iter().map(|(variant, attrs)| {
+        let sub_name = attrs.cased_name();
+        let variant_name = &variant.ident;
+        let constructor_block = match variant.fields {
+            Named(ref fields) => args::gen_constructor(&fields.named, attrs),
+            Unit => quote!(),
+            Unnamed(ref fields) if fields.unnamed.len() == 1 => {
+                let ty = &fields.unnamed[0];
+                quote!( ( <#ty as clap::FromArgMatches>::from_arg_matches(__clap_arg_matches)? ) )
+            }
+            Unnamed(..) => abort_call_site!("{}: tuple enums are not supported", variant.ident),
+        };
+
+        if cfg!(feature = "unstable-v4") {
+            quote! {
+                if #sub_name == #subcommand_name_var && !#sub_arg_matches_var.is_present("") {
+                    return ::std::result::Result::Ok(#name :: #variant_name #constructor_block)
+                }
+            }
+        } else {
+            quote! {
+                if #sub_name == #subcommand_name_var {
+                    return ::std::result::Result::Ok(#name :: #variant_name #constructor_block)
+                }
+            }
+        }
+    });
+    let child_subcommands = flatten_variants.iter().map(|(variant, _attrs)| {
+        let variant_name = &variant.ident;
+        match variant.fields {
+            Unnamed(ref fields) if fields.unnamed.len() == 1 => {
+                let ty = &fields.unnamed[0];
+                quote! {
+                    if <#ty as clap::Subcommand>::has_subcommand(__clap_name) {
+                        let __clap_res = <#ty as clap::FromArgMatches>::from_arg_matches(__clap_arg_matches)?;
+                        return ::std::result::Result::Ok(#name :: #variant_name (__clap_res));
+                    }
+                }
+            }
+            _ => abort!(
+                variant,
+                "`flatten` is usable only with single-typed tuple variants"
+            ),
+        }
+    });
+
+    let wildcard = match ext_subcmd {
+        Some((span, var_name, str_ty, values_of)) => quote_spanned! { span=>
+                ::std::result::Result::Ok(#name::#var_name(
+                    ::std::iter::once(#str_ty::from(#subcommand_name_var))
+                    .chain(
+                        #sub_arg_matches_var.#values_of("").into_iter().flatten().map(#str_ty::from)
+                    )
+                    .collect::<::std::vec::Vec<_>>()
+                ))
+        },
+
+        None => quote! {
+            ::std::result::Result::Err(clap::Error::raw(clap::ErrorKind::UnrecognizedSubcommand, format!("The subcommand '{}' wasn't recognized", #subcommand_name_var)))
+        },
+    };
+
+    quote! {
+        fn from_arg_matches(__clap_arg_matches: &clap::ArgMatches) -> ::std::result::Result<Self, clap::Error> {
+            if let Some((#subcommand_name_var, #sub_arg_matches_var)) = __clap_arg_matches.subcommand() {
+                {
+                    let __clap_arg_matches = #sub_arg_matches_var;
+                    #( #subcommands )*
+                }
+
+                #( #child_subcommands )else*
+
+                #wildcard
+            } else {
+                ::std::result::Result::Err(clap::Error::raw(clap::ErrorKind::MissingSubcommand, "A subcommand is required but one was not provided."))
+            }
+        }
+    }
+}
+
+fn gen_update_from_arg_matches(
+    name: &Ident,
+    variants: &Punctuated<Variant, Token![,]>,
+    parent_attribute: &Attrs,
+) -> TokenStream {
+    use syn::Fields::*;
+
+    let (flatten, variants): (Vec<_>, Vec<_>) = variants
+        .iter()
+        .filter_map(|variant| {
+            let attrs = Attrs::from_variant(
+                variant,
+                parent_attribute.casing(),
+                parent_attribute.env_casing(),
+            );
+
+            match &*attrs.kind() {
+                // Fallback to `from_arg_matches`
+                Kind::ExternalSubcommand => None,
+                _ => Some((variant, attrs)),
+            }
+        })
+        .partition(|(_, attrs)| {
+            let kind = attrs.kind();
+            matches!(&*kind, Kind::Flatten)
+        });
+
+    let subcommands = variants.iter().map(|(variant, attrs)| {
+        let sub_name = attrs.cased_name();
+        let variant_name = &variant.ident;
+        let (pattern, updater) = match variant.fields {
+            Named(ref fields) => {
+                let (fields, update): (Vec<_>, Vec<_>) = fields
+                    .named
+                    .iter()
+                    .map(|field| {
+                        let attrs = Attrs::from_field(
+                            field,
+                            parent_attribute.casing(),
+                            parent_attribute.env_casing(),
+                        );
+                        let field_name = field.ident.as_ref().unwrap();
+                        (
+                            quote!( ref mut #field_name ),
+                            args::gen_updater(&fields.named, &attrs, false),
+                        )
+                    })
+                    .unzip();
+                (quote!( { #( #fields, )* }), quote!( { #( #update )* } ))
+            }
+            Unit => (quote!(), quote!({})),
+            Unnamed(ref fields) => {
+                if fields.unnamed.len() == 1 {
+                    (
+                        quote!((ref mut __clap_arg)),
+                        quote!(clap::FromArgMatches::update_from_arg_matches(
+                            __clap_arg,
+                            __clap_sub_arg_matches
+                        )?),
+                    )
+                } else {
+                    abort_call_site!("{}: tuple enums are not supported", variant.ident)
+                }
+            }
+        };
+
+        quote! {
+            #name :: #variant_name #pattern if #sub_name == __clap_name => {
+                let __clap_arg_matches = __clap_sub_arg_matches;
+                #updater
+            }
+        }
+    });
+
+    let child_subcommands = flatten.iter().map(|(variant, _attrs)| {
+        let variant_name = &variant.ident;
+        match variant.fields {
+            Unnamed(ref fields) if fields.unnamed.len() == 1 => {
+                let ty = &fields.unnamed[0];
+                quote! {
+                    if <#ty as clap::Subcommand>::has_subcommand(__clap_name) {
+                        if let #name :: #variant_name (child) = s {
+                            <#ty as clap::FromArgMatches>::update_from_arg_matches(child, __clap_arg_matches)?;
+                            return ::std::result::Result::Ok(());
+                        }
+                    }
+                }
+            }
+            _ => abort!(
+                variant,
+                "`flatten` is usable only with single-typed tuple variants"
+            ),
+        }
+    });
+
+    quote! {
+        fn update_from_arg_matches<'b>(
+            &mut self,
+            __clap_arg_matches: &clap::ArgMatches,
+        ) -> ::std::result::Result<(), clap::Error> {
+            if let Some((__clap_name, __clap_sub_arg_matches)) = __clap_arg_matches.subcommand() {
+                match self {
+                    #( #subcommands ),*
+                    s => {
+                        #( #child_subcommands )*
+                        *s = <Self as clap::FromArgMatches>::from_arg_matches(__clap_arg_matches)?;
+                    }
+                }
+            }
+            ::std::result::Result::Ok(())
+        }
+    }
+}
diff --git a/third_party/rust/clap_derive/src/dummies.rs b/third_party/rust/clap_derive/src/dummies.rs
new file mode 100644
index 0000000000..be1583062b
--- /dev/null
+++ b/third_party/rust/clap_derive/src/dummies.rs
@@ -0,0 +1,91 @@
+//! Dummy implementations that we emit along with an error.
+
+use proc_macro2::Ident;
+use proc_macro_error::append_dummy;
+use quote::quote;
+
+pub fn parser_struct(name: &Ident) {
+    into_app(name);
+    args(name);
+    append_dummy(quote!( impl clap::Parser for #name {} ));
+}
+
+pub fn parser_enum(name: &Ident) {
+    into_app(name);
+    subcommand(name);
+    append_dummy(quote!( impl clap::Parser for #name {} ));
+}
+
+pub fn into_app(name: &Ident) {
+    append_dummy(quote! {
+        #[allow(deprecated)]
+        impl clap::CommandFactory for #name {
+            fn into_app<'b>() -> clap::Command<'b> {
+                unimplemented!()
+            }
+            fn into_app_for_update<'b>() -> clap::Command<'b> {
+                unimplemented!()
+            }
+        }
+    });
+}
+
+pub fn from_arg_matches(name: &Ident) {
+    append_dummy(quote! {
+        impl clap::FromArgMatches for #name {
+            fn from_arg_matches(_m: &clap::ArgMatches) -> ::std::result::Result<Self, clap::Error> {
+                unimplemented!()
+            }
+            fn update_from_arg_matches(&mut self, matches: &clap::ArgMatches) -> ::std::result::Result<(), clap::Error>{
+                unimplemented!()
+            }
+        }
+    });
+}
+
+pub fn subcommand(name: &Ident) {
+    from_arg_matches(name);
+    append_dummy(quote! {
+        impl clap::Subcommand for #name {
+            fn augment_subcommands(_cmd: clap::Command<'_>) -> clap::Command<'_> {
+                unimplemented!()
+            }
+            fn augment_subcommands_for_update(_cmd: clap::Command<'_>) -> clap::Command<'_> {
+                unimplemented!()
+            }
+            fn has_subcommand(name: &str) -> bool {
+                unimplemented!()
+            }
+        }
+    });
+}
+
+pub fn args(name: &Ident) {
+    from_arg_matches(name);
+    append_dummy(quote! {
+        impl clap::Args for #name {
+            fn augment_args(_cmd: clap::Command<'_>) -> clap::Command<'_> {
+                unimplemented!()
+            }
+            fn augment_args_for_update(_cmd: clap::Command<'_>) -> clap::Command<'_> {
+                unimplemented!()
+            }
+        }
+    });
+}
+
+pub fn arg_enum(name: &Ident) {
+    append_dummy(quote! {
+        impl clap::ArgEnum for #name {
+            fn value_variants<'a>() -> &'a [Self]{
+                unimplemented!()
+            }
+            fn from_str(_input: &str, _ignore_case: bool) -> ::std::result::Result<Self, String> {
+                unimplemented!()
+            }
+            fn to_possible_value<'a>(&self) -> ::std::option::Option<clap::PossibleValue<'a>>{
+                unimplemented!()
+            }
+        }
+    })
+}
diff --git a/third_party/rust/clap_derive/src/lib.rs b/third_party/rust/clap_derive/src/lib.rs
new file mode 100644
index 0000000000..973b61e177
--- /dev/null
+++ b/third_party/rust/clap_derive/src/lib.rs
@@ -0,0 +1,66 @@
+// Copyright 2018 Guillaume Pinot (@TeXitoi) <texitoi@texitoi.eu>,
+// Kevin Knapp (@kbknapp) <kbknapp@gmail.com>, and
+// Ana Hobden (@hoverbear) <operator@hoverbear.org>
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+//
+// This work was derived from Structopt (https://github.com/TeXitoi/structopt)
+// commit#ea76fa1b1b273e65e3b0b1046643715b49bec51f which is licensed under the
+// MIT/Apache 2.0 license.
+
+#![doc(html_logo_url = "https://raw.githubusercontent.com/clap-rs/clap/master/assets/clap.png")]
+#![doc = include_str!("../README.md")]
+#![forbid(unsafe_code)]
+
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+use proc_macro_error::proc_macro_error;
+use syn::{parse_macro_input, DeriveInput};
+
+mod attrs;
+mod derives;
+mod dummies;
+mod parse;
+mod utils;
+
+/// Generates the `ArgEnum` impl.
+#[proc_macro_derive(ArgEnum, attributes(clap))]
+#[proc_macro_error]
+pub fn arg_enum(input: TokenStream) -> TokenStream {
+    let input: DeriveInput = parse_macro_input!(input);
+    derives::derive_arg_enum(&input).into()
+}
+
+/// Generates the `Parser` implementation.
+///
+/// This is far less verbose than defining the `clap::Command` struct manually,
+/// receiving an instance of `clap::ArgMatches` from conducting parsing, and then
+/// implementing a conversion code to instantiate an instance of the user
+/// context struct.
+#[proc_macro_derive(Parser, attributes(clap, structopt))]
+#[proc_macro_error]
+pub fn parser(input: TokenStream) -> TokenStream {
+    let input: DeriveInput = parse_macro_input!(input);
+    derives::derive_parser(&input).into()
+}
+
+/// Generates the `Subcommand` impl.
+#[proc_macro_derive(Subcommand, attributes(clap))]
+#[proc_macro_error]
+pub fn subcommand(input: TokenStream) -> TokenStream {
+    let input: DeriveInput = parse_macro_input!(input);
+    derives::derive_subcommand(&input).into()
+}
+
+/// Generates the `Args` impl.
+#[proc_macro_derive(Args, attributes(clap))]
+#[proc_macro_error]
+pub fn args(input: TokenStream) -> TokenStream {
+    let input: DeriveInput = parse_macro_input!(input);
+    derives::derive_args(&input).into()
+}
diff --git a/third_party/rust/clap_derive/src/parse.rs b/third_party/rust/clap_derive/src/parse.rs
new file mode 100644
index 0000000000..2973cf670f
--- /dev/null
+++ b/third_party/rust/clap_derive/src/parse.rs
@@ -0,0 +1,279 @@
+use std::iter::FromIterator;
+
+use proc_macro_error::{abort, ResultExt};
+use quote::ToTokens;
+use syn::{
+    self, parenthesized,
+    parse::{Parse, ParseBuffer, ParseStream},
+    punctuated::Punctuated,
+    Attribute, Expr, ExprLit, Ident, Lit, LitBool, LitStr, Token,
+};
+
+pub fn parse_clap_attributes(all_attrs: &[Attribute]) -> Vec<ClapAttr> {
+    all_attrs
+        .iter()
+        .filter(|attr| attr.path.is_ident("clap") || attr.path.is_ident("structopt"))
+        .flat_map(|attr| {
+            attr.parse_args_with(Punctuated::<ClapAttr, Token![,]>::parse_terminated)
+                .unwrap_or_abort()
+        })
+        .collect()
+}
+
+#[allow(clippy::large_enum_variant)]
+#[derive(Clone)]
+pub enum ClapAttr {
+    // single-identifier attributes
+    Short(Ident),
+    Long(Ident),
+    Env(Ident),
+    Flatten(Ident),
+    ArgEnum(Ident),
+    FromGlobal(Ident),
+    Subcommand(Ident),
+    VerbatimDocComment(Ident),
+    ExternalSubcommand(Ident),
+    About(Ident),
+    Author(Ident),
+    Version(Ident),
+
+    // ident = "string literal"
+    RenameAllEnv(Ident, LitStr),
+    RenameAll(Ident, LitStr),
+    NameLitStr(Ident, LitStr),
+
+    // parse(parser_kind [= parser_func])
+    Parse(Ident, ParserSpec),
+
+    // ident [= arbitrary_expr]
+    Skip(Ident, Option<Expr>),
+
+    // ident = arbitrary_expr
+    NameExpr(Ident, Expr),
+    DefaultValueT(Ident, Option<Expr>),
+    DefaultValueOsT(Ident, Option<Expr>),
+    NextDisplayOrder(Ident, Expr),
+    NextHelpHeading(Ident, Expr),
+    HelpHeading(Ident, Expr),
+
+    // ident(arbitrary_expr,*)
+    MethodCall(Ident, Vec<Expr>),
+}
+
+impl Parse for ClapAttr {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        use self::ClapAttr::*;
+
+        let name: Ident = input.parse()?;
+        let name_str = name.to_string();
+
+        if input.peek(Token![=]) {
+            // `name = value` attributes.
+            let assign_token = input.parse::<Token![=]>()?; // skip '='
+
+            if input.peek(LitStr) {
+                let lit: LitStr = input.parse()?;
+
+                match &*name_str {
+                    "rename_all" => Ok(RenameAll(name, lit)),
+                    "rename_all_env" => Ok(RenameAllEnv(name, lit)),
+
+                    "skip" => {
+                        let expr = ExprLit {
+                            attrs: vec![],
+                            lit: Lit::Str(lit),
+                        };
+                        let expr = Expr::Lit(expr);
+                        Ok(Skip(name, Some(expr)))
+                    }
+
+                    "next_display_order" => {
+                        let expr = ExprLit {
+                            attrs: vec![],
+                            lit: Lit::Str(lit),
+                        };
+                        let expr = Expr::Lit(expr);
+                        Ok(NextDisplayOrder(name, expr))
+                    }
+
+                    "next_help_heading" => {
+                        let expr = ExprLit {
+                            attrs: vec![],
+                            lit: Lit::Str(lit),
+                        };
+                        let expr = Expr::Lit(expr);
+                        Ok(NextHelpHeading(name, expr))
+                    }
+                    "help_heading" => {
+                        let expr = ExprLit {
+                            attrs: vec![],
+                            lit: Lit::Str(lit),
+                        };
+                        let expr = Expr::Lit(expr);
+                        Ok(HelpHeading(name, expr))
+                    }
+
+                    _ => Ok(NameLitStr(name, lit)),
+                }
+            } else {
+                match input.parse::<Expr>() {
+                    Ok(expr) => match &*name_str {
+                        "skip" => Ok(Skip(name, Some(expr))),
+                        "default_value_t" => Ok(DefaultValueT(name, Some(expr))),
+                        "default_value_os_t" => Ok(DefaultValueOsT(name, Some(expr))),
+                        "next_display_order" => Ok(NextDisplayOrder(name, expr)),
+                        "next_help_heading" => Ok(NextHelpHeading(name, expr)),
+                        "help_heading" => Ok(HelpHeading(name, expr)),
+                        _ => Ok(NameExpr(name, expr)),
+                    },
+
+                    Err(_) => abort! {
+                        assign_token,
+                        "expected `string literal` or `expression` after `=`"
+                    },
+                }
+            }
+        } else if input.peek(syn::token::Paren) {
+            // `name(...)` attributes.
+            let nested;
+            parenthesized!(nested in input);
+
+            match name_str.as_ref() {
+                "parse" => {
+                    let parser_specs: Punctuated<ParserSpec, Token![,]> =
+                        nested.parse_terminated(ParserSpec::parse)?;
+
+                    if parser_specs.len() == 1 {
+                        Ok(Parse(name, parser_specs[0].clone()))
+                    } else {
+                        abort!(name, "parse must have exactly one argument")
+                    }
+                }
+
+                "raw" => match nested.parse::<LitBool>() {
+                    Ok(bool_token) => {
+                        let expr = ExprLit {
+                            attrs: vec![],
+                            lit: Lit::Bool(bool_token),
+                        };
+                        let expr = Expr::Lit(expr);
+                        Ok(MethodCall(name, vec![expr]))
+                    }
+
+                    Err(_) => {
+                        abort!(name,
+                            "`#[clap(raw(...))` attributes are removed, \
+                            they are replaced with raw methods";
+                            help = "if you meant to call `clap::Arg::raw()` method \
+                                you should use bool literal, like `raw(true)` or `raw(false)`";
+                            note = raw_method_suggestion(nested);
+                        );
+                    }
+                },
+
+                _ => {
+                    let method_args: Punctuated<_, Token![,]> =
+                        nested.parse_terminated(Expr::parse)?;
+                    Ok(MethodCall(name, Vec::from_iter(method_args)))
+                }
+            }
+        } else {
+            // Attributes represented with a sole identifier.
+            match name_str.as_ref() {
+                "long" => Ok(Long(name)),
+                "short" => Ok(Short(name)),
+                "env" => Ok(Env(name)),
+                "flatten" => Ok(Flatten(name)),
+                "arg_enum" => Ok(ArgEnum(name)),
+                "from_global" => Ok(FromGlobal(name)),
+                "subcommand" => Ok(Subcommand(name)),
+                "external_subcommand" => Ok(ExternalSubcommand(name)),
+                "verbatim_doc_comment" => Ok(VerbatimDocComment(name)),
+
+                "default_value" => {
+                    abort!(name,
+                        "`#[clap(default_value)` attribute (without a value) has been replaced by `#[clap(default_value_t)]`.";
+                        help = "Change the attribute to `#[clap(default_value_t)]`";
+                    )
+                }
+                "default_value_t" => Ok(DefaultValueT(name, None)),
+                "default_value_os_t" => Ok(DefaultValueOsT(name, None)),
+                "about" => (Ok(About(name))),
+                "author" => (Ok(Author(name))),
+                "version" => Ok(Version(name)),
+
+                "skip" => Ok(Skip(name, None)),
+
+                _ => abort!(name, "unexpected attribute: {}", name_str),
+            }
+        }
+    }
+}
+
+#[derive(Clone)]
+pub struct ParserSpec {
+    pub kind: Ident,
+    pub eq_token: Option<Token![=]>,
+    pub parse_func: Option<Expr>,
+}
+
+impl Parse for ParserSpec {
+    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
+        let kind = input
+            .parse()
+            .map_err(|_| input.error("parser specification must start with identifier"))?;
+        let eq_token = input.parse()?;
+        let parse_func = match eq_token {
+            None => None,
+            Some(_) => Some(input.parse()?),
+        };
+        Ok(ParserSpec {
+            kind,
+            eq_token,
+            parse_func,
+        })
+    }
+}
+
+fn raw_method_suggestion(ts: ParseBuffer) -> String {
+    let do_parse = move || -> Result<(Ident, Punctuated<Expr, Token![,]>), syn::Error> {
+        let name = ts.parse()?;
+        let _eq: Token![=] = ts.parse()?;
+        let val: LitStr = ts.parse()?;
+        let exprs = val.parse_with(Punctuated::<Expr, Token![,]>::parse_terminated)?;
+        Ok((name, exprs))
+    };
+
+    fn to_string<T: ToTokens>(val: &T) -> String {
+        val.to_token_stream()
+            .to_string()
+            .replace(' ', "")
+            .replace(',', ", ")
+    }
+
+    if let Ok((name, exprs)) = do_parse() {
+        let suggestion = if exprs.len() == 1 {
+            let val = to_string(&exprs[0]);
+            format!(" = {}", val)
+        } else {
+            let val = exprs
+                .into_iter()
+                .map(|expr| to_string(&expr))
+                .collect::<Vec<_>>()
+                .join(", ");
+
+            format!("({})", val)
+        };
+
+        format!(
+            "if you need to call `clap::Arg/Command::{}` method you \
+             can do it like this: #[clap({}{})]",
+            name, name, suggestion
+        )
+    } else {
+        "if you need to call some method from `clap::Arg/Command` \
+         you should use raw method, see \
+         https://github.com/clap-rs/clap/blob/master/examples/derive_ref/README.md#raw-attributes"
+            .into()
+    }
+}
diff --git a/third_party/rust/clap_derive/src/utils/doc_comments.rs b/third_party/rust/clap_derive/src/utils/doc_comments.rs
new file mode 100644
index 0000000000..f0a5034d70
--- /dev/null
+++ b/third_party/rust/clap_derive/src/utils/doc_comments.rs
@@ -0,0 +1,107 @@
+//! The preprocessing we apply to doc comments.
+//!
+//! #[derive(Parser)] works in terms of "paragraphs". Paragraph is a sequence of
+//! non-empty adjacent lines, delimited by sequences of blank (whitespace only) lines.
+
+use crate::attrs::Method;
+
+use quote::{format_ident, quote};
+use std::iter;
+
+pub fn process_doc_comment(lines: Vec<String>, name: &str, preprocess: bool) -> Vec<Method> {
+    // multiline comments (`/** ... */`) may have LFs (`\n`) in them,
+    // we need to split so we could handle the lines correctly
+    //
+    // we also need to remove leading and trailing blank lines
+    let mut lines: Vec<&str> = lines
+        .iter()
+        .skip_while(|s| is_blank(s))
+        .flat_map(|s| s.split('\n'))
+        .collect();
+
+    while let Some(true) = lines.last().map(|s| is_blank(s)) {
+        lines.pop();
+    }
+
+    // remove one leading space no matter what
+    for line in lines.iter_mut() {
+        if line.starts_with(' ') {
+            *line = &line[1..];
+        }
+    }
+
+    if lines.is_empty() {
+        return vec![];
+    }
+
+    let short_name = format_ident!("{}", name);
+    let long_name = format_ident!("long_{}", name);
+
+    if let Some(first_blank) = lines.iter().position(|s| is_blank(s)) {
+        let (short, long) = if preprocess {
+            let paragraphs = split_paragraphs(&lines);
+            let short = paragraphs[0].clone();
+            let long = paragraphs.join("\n\n");
+            (remove_period(short), long)
+        } else {
+            let short = lines[..first_blank].join("\n");
+            let long = lines.join("\n");
+            (short, long)
+        };
+
+        vec![
+            Method::new(short_name, quote!(#short)),
+            Method::new(long_name, quote!(#long)),
+        ]
+    } else {
+        let short = if preprocess {
+            let s = merge_lines(&lines);
+            remove_period(s)
+        } else {
+            lines.join("\n")
+        };
+
+        vec![
+            Method::new(short_name, quote!(#short)),
+            Method::new(long_name, quote!(None)),
+        ]
+    }
+}
+
+fn split_paragraphs(lines: &[&str]) -> Vec<String> {
+    let mut last_line = 0;
+    iter::from_fn(|| {
+        let slice = &lines[last_line..];
+        let start = slice.iter().position(|s| !is_blank(s)).unwrap_or(0);
+
+        let slice = &slice[start..];
+        let len = slice
+            .iter()
+            .position(|s| is_blank(s))
+            .unwrap_or(slice.len());
+
+        last_line += start + len;
+
+        if len != 0 {
+            Some(merge_lines(&slice[..len]))
+        } else {
+            None
+        }
+    })
+    .collect()
+}
+
+fn remove_period(mut s: String) -> String {
+    if s.ends_with('.') && !s.ends_with("..") {
+        s.pop();
+    }
+    s
+}
+
+fn is_blank(s: &str) -> bool {
+    s.trim().is_empty()
+}
+
+fn merge_lines(lines: &[&str]) -> String {
+    lines.iter().map(|s| s.trim()).collect::<Vec<_>>().join(" ")
+}
diff --git a/third_party/rust/clap_derive/src/utils/mod.rs b/third_party/rust/clap_derive/src/utils/mod.rs
new file mode 100644
index 0000000000..77a467c754
--- /dev/null
+++ b/third_party/rust/clap_derive/src/utils/mod.rs
@@ -0,0 +1,9 @@
+mod doc_comments;
+mod spanned;
+mod ty;
+
+pub use self::{
+    doc_comments::process_doc_comment,
+    spanned::Sp,
+    ty::{inner_type, is_simple_ty, sub_type, subty_if_name, Ty},
+};
diff --git a/third_party/rust/clap_derive/src/utils/spanned.rs b/third_party/rust/clap_derive/src/utils/spanned.rs
new file mode 100644
index 0000000000..11415f6f0e
--- /dev/null
+++ b/third_party/rust/clap_derive/src/utils/spanned.rs
@@ -0,0 +1,92 @@
+use proc_macro2::{Ident, Span, TokenStream};
+use quote::ToTokens;
+use syn::LitStr;
+
+use std::ops::{Deref, DerefMut};
+
+/// An entity with a span attached.
+#[derive(Debug, Clone)]
+pub struct Sp<T> {
+    val: T,
+    span: Span,
+}
+
+impl<T> Sp<T> {
+    pub fn new(val: T, span: Span) -> Self {
+        Sp { val, span }
+    }
+
+    pub fn call_site(val: T) -> Self {
+        Sp {
+            val,
+            span: Span::call_site(),
+        }
+    }
+
+    pub fn span(&self) -> Span {
+        self.span
+    }
+}
+
+impl<T> Deref for Sp<T> {
+    type Target = T;
+
+    fn deref(&self) -> &T {
+        &self.val
+    }
+}
+
+impl<T> DerefMut for Sp<T> {
+    fn deref_mut(&mut self) -> &mut T {
+        &mut self.val
+    }
+}
+
+impl From<Ident> for Sp<String> {
+    fn from(ident: Ident) -> Self {
+        Sp {
+            val: ident.to_string(),
+            span: ident.span(),
+        }
+    }
+}
+
+impl From<LitStr> for Sp<String> {
+    fn from(lit: LitStr) -> Self {
+        Sp {
+            val: lit.value(),
+            span: lit.span(),
+        }
+    }
+}
+
+impl<'a> From<Sp<&'a str>> for Sp<String> {
+    fn from(sp: Sp<&'a str>) -> Self {
+        Sp::new(sp.val.into(), sp.span)
+    }
+}
+
+impl<U, T: PartialEq<U>> PartialEq<U> for Sp<T> {
+    fn eq(&self, other: &U) -> bool {
+        self.val == *other
+    }
+}
+
+impl<T: AsRef<str>> AsRef<str> for Sp<T> {
+    fn as_ref(&self) -> &str {
+        self.val.as_ref()
+    }
+}
+
+impl<T: ToTokens> ToTokens for Sp<T> {
+    fn to_tokens(&self, stream: &mut TokenStream) {
+        // this is the simplest way out of correct ones to change span on
+        // arbitrary token tree I could come up with
+        let tt = self.val.to_token_stream().into_iter().map(|mut tt| {
+            tt.set_span(self.span);
+            tt
+        });
+
+        stream.extend(tt);
+    }
+}
diff --git a/third_party/rust/clap_derive/src/utils/ty.rs b/third_party/rust/clap_derive/src/utils/ty.rs
new file mode 100644
index 0000000000..891aa37d68
--- /dev/null
+++ b/third_party/rust/clap_derive/src/utils/ty.rs
@@ -0,0 +1,121 @@
+//! Special types handling
+
+use super::spanned::Sp;
+
+use syn::{
+    spanned::Spanned, GenericArgument, Path, PathArguments, PathArguments::AngleBracketed,
+    PathSegment, Type, TypePath,
+};
+
+#[derive(Copy, Clone, PartialEq, Debug)]
+pub enum Ty {
+    Bool,
+    Vec,
+    Option,
+    OptionOption,
+    OptionVec,
+    Other,
+}
+
+impl Ty {
+    pub fn from_syn_ty(ty: &syn::Type) -> Sp<Self> {
+        use self::Ty::*;
+        let t = |kind| Sp::new(kind, ty.span());
+
+        if is_simple_ty(ty, "bool") {
+            t(Bool)
+        } else if is_generic_ty(ty, "Vec") {
+            t(Vec)
+        } else if let Some(subty) = subty_if_name(ty, "Option") {
+            if is_generic_ty(subty, "Option") {
+                t(OptionOption)
+            } else if is_generic_ty(subty, "Vec") {
+                t(OptionVec)
+            } else {
+                t(Option)
+            }
+        } else {
+            t(Other)
+        }
+    }
+}
+
+pub fn inner_type(ty: Ty, field_ty: &syn::Type) -> &syn::Type {
+    match ty {
+        Ty::Vec | Ty::Option => sub_type(field_ty).unwrap_or(field_ty),
+        Ty::OptionOption | Ty::OptionVec => {
+            sub_type(field_ty).and_then(sub_type).unwrap_or(field_ty)
+        }
+        _ => field_ty,
+    }
+}
+
+pub fn sub_type(ty: &syn::Type) -> Option<&syn::Type> {
+    subty_if(ty, |_| true)
+}
+
+fn only_last_segment(mut ty: &syn::Type) -> Option<&PathSegment> {
+    while let syn::Type::Group(syn::TypeGroup { elem, .. }) = ty {
+        ty = elem;
+    }
+    match ty {
+        Type::Path(TypePath {
+            qself: None,
+            path:
+                Path {
+                    leading_colon: None,
+                    segments,
+                },
+        }) => only_one(segments.iter()),
+
+        _ => None,
+    }
+}
+
+fn subty_if<F>(ty: &syn::Type, f: F) -> Option<&syn::Type>
+where
+    F: FnOnce(&PathSegment) -> bool,
+{
+    only_last_segment(ty)
+        .filter(|segment| f(segment))
+        .and_then(|segment| {
+            if let AngleBracketed(args) = &segment.arguments {
+                only_one(args.args.iter()).and_then(|genneric| {
+                    if let GenericArgument::Type(ty) = genneric {
+                        Some(ty)
+                    } else {
+                        None
+                    }
+                })
+            } else {
+                None
+            }
+        })
+}
+
+pub fn subty_if_name<'a>(ty: &'a syn::Type, name: &str) -> Option<&'a syn::Type> {
+    subty_if(ty, |seg| seg.ident == name)
+}
+
+pub fn is_simple_ty(ty: &syn::Type, name: &str) -> bool {
+    only_last_segment(ty)
+        .map(|segment| {
+            if let PathArguments::None = segment.arguments {
+                segment.ident == name
+            } else {
+                false
+            }
+        })
+        .unwrap_or(false)
+}
+
+fn is_generic_ty(ty: &syn::Type, name: &str) -> bool {
+    subty_if_name(ty, name).is_some()
+}
+
+fn only_one<I, T>(mut iter: I) -> Option<T>
+where
+    I: Iterator<Item = T>,
+{
+    iter.next().filter(|_| iter.next().is_none())
+}