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|
//! **Transactions** are the only way make changes to the ref store in order to increase the chance of consistency in a multi-threaded
//! environment.
//!
//! Transactions currently allow to…
//!
//! * create or update reference
//! * delete references
//!
//! The following guarantees are made:
//!
//! * transactions are prepared which is when other writers are prevented from changing them
//! - errors during preparations will cause a perfect rollback
//! * prepared transactions are committed to finalize the change
//! - errors when committing while leave the ref store in an inconsistent, but operational state.
use gix_object::bstr::BString;
use crate::{FullName, Target};
/// A change to the reflog.
#[derive(PartialEq, Eq, Debug, Hash, Ord, PartialOrd, Clone)]
pub struct LogChange {
/// How to treat the reference log.
pub mode: RefLog,
/// If set, create a reflog even though it would otherwise not be the case as prohibited by general rules.
/// Note that ref-log writing might be prohibited in the entire repository which is when this flag has no effect either.
pub force_create_reflog: bool,
/// The message to put into the reference log. It must be a single line, hence newlines are forbidden.
/// The string can be empty to indicate there should be no message at all.
pub message: BString,
}
impl Default for LogChange {
fn default() -> Self {
LogChange {
mode: RefLog::AndReference,
force_create_reflog: false,
message: Default::default(),
}
}
}
/// The desired value of an updated value
#[derive(PartialEq, Eq, Debug, Hash, Ord, PartialOrd, Clone)]
pub enum PreviousValue {
/// No requirements are made towards the current value, and the new value is set unconditionally.
Any,
/// The reference must exist and may have any value.
MustExist,
/// Create the ref only, hence the reference must not exist.
MustNotExist,
/// The ref _must_ exist and have the given value.
MustExistAndMatch(Target),
/// The ref _may_ exist and have the given value, or may not exist at all.
ExistingMustMatch(Target),
}
/// A description of an edit to perform.
#[derive(PartialEq, Eq, Debug, Hash, Ord, PartialOrd, Clone)]
pub enum Change {
/// If previous is not `None`, the ref must exist and its `oid` must agree with the `previous`, and
/// we function like `update`.
/// Otherwise it functions as `create-or-update`.
Update {
/// The desired change to the reference log.
log: LogChange,
/// The expected value already present in the reference.
/// If a ref was existing previously it will be overwritten at `MustExistAndMatch(actual_value)` for use after
/// the transaction was committed successfully.
expected: PreviousValue,
/// The new state of the reference, either for updating an existing one or creating a new one.
new: Target,
},
/// Delete a reference and optionally check if `previous` is its content.
Delete {
/// The expected value of the reference, with the `MustNotExist` variant being invalid.
///
/// If a previous ref existed, this value will be filled in automatically as `MustExistAndMatch(actual_value)` and
/// can be accessed if the transaction was committed successfully.
expected: PreviousValue,
/// How to treat the reference log during deletion.
log: RefLog,
},
}
impl Change {
/// Return references to values that are the new value after the change is applied, if this is an update.
pub fn new_value(&self) -> Option<crate::TargetRef<'_>> {
match self {
Change::Update { new, .. } => new.to_ref().into(),
Change::Delete { .. } => None,
}
}
/// Return references to values that are in common between all variants and denote the previous observed value.
pub fn previous_value(&self) -> Option<crate::TargetRef<'_>> {
match self {
// TODO: use or-patterns once MRV is larger than 1.52 (and this is supported)
Change::Update {
expected: PreviousValue::MustExistAndMatch(previous) | PreviousValue::ExistingMustMatch(previous),
..
}
| Change::Delete {
expected: PreviousValue::MustExistAndMatch(previous) | PreviousValue::ExistingMustMatch(previous),
..
} => previous,
_ => return None,
}
.to_ref()
.into()
}
}
/// A reference that is to be changed
#[derive(PartialEq, Eq, Debug, Hash, Ord, PartialOrd, Clone)]
pub struct RefEdit {
/// The change itself
pub change: Change,
/// The name of the reference to apply the change to
pub name: FullName,
/// If set, symbolic references identified by `name` will be dereferenced to have the `change` applied to their target.
/// This flag has no effect if the reference isn't symbolic.
pub deref: bool,
}
/// The way to deal with the Reflog in deletions.
#[derive(PartialEq, Eq, Debug, Hash, Ord, PartialOrd, Clone, Copy)]
pub enum RefLog {
/// Delete or update the reference and the log
AndReference,
/// Delete or update only the reflog
Only,
}
mod ext;
pub use ext::RefEditsExt;
|
