2 files changed, 108 insertions, 0 deletions
diff --git a/vendor/gix-odb/src/alternate/mod.rs b/vendor/gix-odb/src/alternate/mod.rs
new file mode 100644
index 000000000..c343ef5aa
--- /dev/null
+++ b/vendor/gix-odb/src/alternate/mod.rs
@@ -0,0 +1,75 @@
+//! A file with directories of other git object databases to use when reading objects.
+//!
+//! This inherently makes alternates read-only.
+//!
+//! An alternate file in `<git-dir>/info/alternates` can look as follows:
+//!
+//! ```text
+//! # a comment, empty lines are also allowed
+//! # relative paths resolve relative to the parent git repository
+//! ../path/relative/to/repo/.git
+//! /absolute/path/to/repo/.git
+//!
+//! "/a/ansi-c-quoted/path/with/tabs\t/.git"
+//!
+//! # each .git directory should indeed be a directory, and not a file
+//! ```
+//!
+//! Based on the [canonical implementation](https://github.com/git/git/blob/master/sha1-file.c#L598:L609).
+use std::{fs, io, path::PathBuf};
+
+use gix_path::realpath::MAX_SYMLINKS;
+
+///
+pub mod parse;
+
+/// Returned by [`resolve()`]
+#[derive(thiserror::Error, Debug)]
+#[allow(missing_docs)]
+pub enum Error {
+    #[error(transparent)]
+    Io(#[from] io::Error),
+    #[error(transparent)]
+    Realpath(#[from] gix_path::realpath::Error),
+    #[error(transparent)]
+    Parse(#[from] parse::Error),
+    #[error("Alternates form a cycle: {} -> {}", .0.iter().map(|p| format!("'{}'", p.display())).collect::<Vec<_>>().join(" -> "), .0.first().expect("more than one directories").display())]
+    Cycle(Vec<PathBuf>),
+}
+
+/// Given an `objects_directory`, try to resolve alternate object directories possibly located in the
+/// `./info/alternates` file into canonical paths and resolve relative paths with the help of the `current_dir`.
+/// If no alternate object database was resolved, the resulting `Vec` is empty (it is not an error
+/// if there are no alternates).
+/// It is an error once a repository is seen again as it would lead to a cycle.
+pub fn resolve(
+    objects_directory: impl Into<PathBuf>,
+    current_dir: impl AsRef<std::path::Path>,
+) -> Result<Vec<PathBuf>, Error> {
+    let relative_base = objects_directory.into();
+    let mut dirs = vec![(0, relative_base.clone())];
+    let mut out = Vec::new();
+    let cwd = current_dir.as_ref();
+    let mut seen = vec![gix_path::realpath_opts(&relative_base, cwd, MAX_SYMLINKS)?];
+    while let Some((depth, dir)) = dirs.pop() {
+        match fs::read(dir.join("info").join("alternates")) {
+            Ok(input) => {
+                for path in parse::content(&input)?.into_iter() {
+                    let path = relative_base.join(path);
+                    let path_canonicalized = gix_path::realpath_opts(&path, cwd, MAX_SYMLINKS)?;
+                    if seen.contains(&path_canonicalized) {
+                        return Err(Error::Cycle(seen));
+                    }
+                    seen.push(path_canonicalized);
+                    dirs.push((depth + 1, path));
+                }
+            }
+            Err(err) if err.kind() == io::ErrorKind::NotFound => {}
+            Err(err) => return Err(err.into()),
+        };
+        if depth != 0 {
+            out.push(dir);
+        }
+    }
+    Ok(out)
+}
diff --git a/vendor/gix-odb/src/alternate/parse.rs b/vendor/gix-odb/src/alternate/parse.rs
new file mode 100644
index 000000000..1c297d153
--- /dev/null
+++ b/vendor/gix-odb/src/alternate/parse.rs
@@ -0,0 +1,33 @@
+use std::{borrow::Cow, path::PathBuf};
+
+use gix_object::bstr::ByteSlice;
+
+/// Returned as part of [`crate::alternate::Error::Parse`]
+#[derive(thiserror::Error, Debug)]
+#[allow(missing_docs)]
+pub enum Error {
+    #[error("Could not obtain an object path for the alternate directory '{}'", String::from_utf8_lossy(.0))]
+    PathConversion(Vec<u8>),
+    #[error("Could not unquote alternate path")]
+    Unquote(#[from] gix_quote::ansi_c::undo::Error),
+}
+
+pub(crate) fn content(input: &[u8]) -> Result<Vec<PathBuf>, Error> {
+    let mut out = Vec::new();
+    for line in input.split(|b| *b == b'\n') {
+        let line = line.as_bstr();
+        if line.is_empty() || line.starts_with(b"#") {
+            continue;
+        }
+        out.push(
+            gix_path::try_from_bstr(if line.starts_with(b"\"") {
+                gix_quote::ansi_c::undo(line)?.0
+            } else {
+                Cow::Borrowed(line)
+            })
+            .map_err(|_| Error::PathConversion(line.to_vec()))?
+            .into_owned(),
+        )
+    }
+    Ok(out)
+}