feat(manager/cargo): support git dependencies

[mkniewallner]

Changes

Add support for git dependencies in cargo manager.

Context

Closes #26531.

Cargo specification: https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html#specifying-dependencies-from-git-repositories.

There is one change I am really not sure about.

Documentation (please check one with an [x])

• I have updated the documentation, or
• No documentation update is required

How I've tested my work (please select one)

I have verified these changes via:

• Code inspection only, or
• Newly added/modified unit tests, or
• No unit tests but ran on a real repository, or
• Both unit tests + ran on a real repository

Tested against https://github.com/mkniewallner/renovate-rust-git-dependencies.

[mkniewallner]

Not fully sure of the logic here, but without this change, we would display a warning that appears in the dependency dashboard when updating git dependencies (warning was added in #25983).

On the overall logic, technically cargo update --precise supports git dependencies, but I think the logic is different that the one for crates.

For instance on https://github.com/mkniewallner/renovate-rust-git-dependencies/blob/2eb824eb730a37b108f1d4eec951c027a031905a/Cargo.toml, when running cargo update without arguments, serde and transitive dependencies will get updated, but git dependencies will be left untouched:

 [[package]]
 name = "serde"
-version = "1.0.213"
+version = "1.0.214"
 
 [[package]]
 name = "serde_derive"
-version = "1.0.213"
+version = "1.0.214"
 
 [[package]]
 name = "syn"
-version = "2.0.85"
+version = "2.0.86"

And trying cargo update ruff_python_parser --precise 0.7.0 will lead to those changes in the lock file:

 [[package]]
 name = "ruff_python_parser"
 version = "0.0.0"
-source = "git+https://github.com/astral-sh/ruff?tag=0.6.1#499c0bd875c3f53c65f542a217b4d9a0962191c3"
+source = "git+https://github.com/astral-sh/ruff?tag=0.6.1#5e6de4e0c69660e8ca8608d1ac965216197756ce"

where the commit do resolve to 0.7.0, but while keeping 0.6.1 tag reference in the source + Cargo.toml, which feels wrong?

[rarkins]

Could you split this back to Discussion - either existing or new - assuming that a design decision needs making? It's hard to follow threads in PR reviews

[mkniewallner]

Hey, sorry for the delay, got quite busy lately. There was one kinda blocker that required some discussion in #32235 (comment). I'll check if it still applies (and also resolve conflicts).