Manage vendored third-party code in git.

In monorepo software projects, it is common to check in code from third-party dependencies into the monorepo (called “vendoring”). This allows the developers of the monorepo to patch the third-party code directly without having to get a change merged upstream.

Managing these vendored projects will often involve cherry-picking upstream commits to fix bugs or exporting patches from the monorepo for use upstream. git-third-party helps with this by allowing cherry-picking commits in separate git repos, optionally adding or removing directory prefixes.

Say you want to vendor the foobar library (from the v1.0 tag) in your git monorepo:

$ cd ~/src/monorepo
$ git third-party clone --squash -s ~/src/foobar -d third_party/foobar v1.0
$ git add third_party/foobar && git commit -m 'foobar: check in v1.0'

After some development, you find a bug and fix it locally in the monorepo. Later, when you want to upstream the fix:

$ cd ~/src/foobar
$ git third-party cherry-pick -s ~/src/monorepo -S third_party/foobar -1 <commit hash>

Then create a pull request with the new commit.

Eventually, foobar v1.1 is released with bugfixes that you want to pull in locally:

$ cd ~/src/monorepo
$ git third-party cherry-pick -s ~/src/foobar -d third_party/foobar v1.1...v1.0