cargo-patch

Cargo-Patch is a Cargo Subcommand which allows patching dependencies using patch files.

Installation

Simply run:

cargo install cargo-patch

Usage

To patch a dependency one has to add the following to Cargo.toml:

[package.metadata.patch.serde]
version = "1.0"
patches = [
    "test.patch"
]

It specifies which dependency to patch (in this case serde) and one or more patchfiles to apply. Running:

cargo patch

will download the serde package specified in the dependency section to the target/patch folder and apply the given patches. To use the patched version one has to override the dependency using replace like this

[patch.crates-io]
serde = { path = './target/patch/serde-1.0.110' }

Patch format

You can either use diff or git to create patch files. Important is that file paths are relative and inside the dependency.

Using diff file generated by GitHub pull request

[package.metadata.patch.serde]
version = "1.0"
patches = [
    { path = "generatedByGithub.patch", source = "GithubPrDiff" },
    { path = "generatedByGithub2.patch", source = "GithubPrDiff" },
    "test.patch",
    "test2.patch"
]

Limitations

It's only possible to patch dependencies of binary crates as it is not possible for a subcommand to intercept the build process.