Provide path feature with git resource

[yanganto]

Problem

We want to use a customized git dependency of a crate in a repository, which have more than one Rust crates and the workspace in not in the root of repository.

Following is a real example from WasmEdge

.
├── bindings
│   └── rust
│       ├── Cargo.toml
│       ├── wasmedge-sdk
│       │   └── Cargo.toml
│       └── wasmedge-sys
│           └── Cargo.toml

166 directories, 717 files

If we can use git and path at the same time, everything will be straight forward for developers.
wasmedge-sys = { git = "wasmedge_git_url", path = "/bindings/rust/wasmedge-sys"}

You can check out the following closed issue, people still there and request this feature.
#1462

Proposed Solution

We need to modify the following structure, and allow using path with git, also the path will be transformed to absolute path before using, such that we can make sure the path will not go out of the resource.

src/cargo/core/source/source_id.rs

  #[derive(Eq, Clone, Debug)]
  struct SourceIdInner {
      /// The source URL.
      url: Url,
      /// The canonical version of the above url
      canonical_url: CanonicalUrl,
      /// The source kind.
      kind: SourceKind,
      /// For example, the exact Git revision of the specified branch for a Git Source.
      precise: Option<String>,
      /// Name of the registry source for alternative registries
      /// WARNING: this is not always set for alt-registries when the name is
      /// not known.
      name: Option<String>,
      /// The portion of resource
+     /// For example, the folder for a Git source
+     portion: Option<String>,
  }

src/cargo/sources/config.rs

  struct SourceConfigDef {
      /// Indicates this source should be replaced with another of the given name.
      replace_with: OptValue<String>,
      /// A directory source.
      directory: Option<ConfigRelativePath>,
      /// A registry source. Value is a URL.
      registry: OptValue<String>,
      /// A local registry source.
      local_registry: Option<ConfigRelativePath>,
      /// A git source. Value is a URL.
      git: OptValue<String>,
      /// The git branch.
      branch: OptValue<String>,
      /// The git tag.
      tag: OptValue<String>,
      /// The git revision.
      rev: OptValue<String>,
+     /// The porton of the Source,
+     /// for example the folder of git resoutce
+     portion: Option<String>,
  }

Notes

No response

[ehuss]

Can you say more about why you would like to specify the path within the git repository? Cargo already searches for the package by name, so unless you have two packages with the exact same name, this should not be necessary.

[yanganto]

Thanks ehuss. It works.

[zapkub]

@ehuss what about the repository contain more than two packages with the same name?