Been using this for a while, mostly when I make a tool as part of a larger project and the tool is big enough to deserve its own release.
It’s powerful enough to do a whole bidirectional shipping operation where you export and import code—no thanks, that’s a hassle. I use it mostly for a simple fire and forget export, where I take a folder out of its original repo and preserve the history. Then I just move development to the new repo. The new project layout can be completely different, but Git blame works and I’m happy with that.
The one-way pattern is actually how Google uses it internally too, syncing outward from their monorepo to GitHub. Bidirectional gets messy because transforms (path remapping, file exclusions, header stripping) are easy to apply in one direction but can't always be cleanly inverted. When both sides have diverged, Copybara's baseline tracking starts producing confusing results because semantically equivalent commits generate different SHAs after transform.
One thing worth knowing: history "preservation" is actually cherry-picks with rewritten commits, not a true transplant. Git blame works because the file content and authorship carry over, but the SHAs are new. Copybara embeds the original SHA in a commit message trailer (GitOrigin-RevId), which is useful to know if you ever need to correlate commits across repos after the fact.
To those who have used it: is it handy for situations where you have multiple repos that want to share a little code, but it's not worth the trouble of extracting a library, referencing it, publishing versioned releases, updating dependent repos, etc?
And instead just "sync" a code folder from one main repo (perhaps containing common domain models) to other repos?
Basically the Go philosophy that a little bit of copying is better than a lot of dependency?
It’s largely used for syncing external open source projects with the monorepo. Policy is to require source code imports over built artifacts. Though you can get exceptions.
Some projects are also developed in the monorepo and exported via Copybara.
My team also uses it to version Starlark rule sets internally.
Source code imports versus artifacts really neither here nor there. Go is source code imports too.
The key part for Copybara is that Google will make changes to the OSS projects from within the internal repo and everyone else will make changes to the OSS projects.
It's for when you have a monorepo internally, and want to publish parts of it as open source to the world. They still need to live in the monorepo, so this is the solution.
Having a public repo as a dependency for your private corporate repo is a pain in the ass development-wise. Having a tree of such dependencies is a migraine.
Copybara can do that but I think it will be annoying and tedious to use it that way. More annoying than the problem of extracting a library or shoving some files in a separate repo.
Interesting. Anyone knows how this compares to using git submodules and subtrees?
I had used those to create separate repo for website artifacts while the same also remain plugged into the webapp dev repo. (Both sides remain modifiable and changes mergeable to the
other side.)
It’s powerful enough to do a whole bidirectional shipping operation where you export and import code—no thanks, that’s a hassle. I use it mostly for a simple fire and forget export, where I take a folder out of its original repo and preserve the history. Then I just move development to the new repo. The new project layout can be completely different, but Git blame works and I’m happy with that.
One thing worth knowing: history "preservation" is actually cherry-picks with rewritten commits, not a true transplant. Git blame works because the file content and authorship carry over, but the SHAs are new. Copybara embeds the original SHA in a commit message trailer (GitOrigin-RevId), which is useful to know if you ever need to correlate commits across repos after the fact.
And instead just "sync" a code folder from one main repo (perhaps containing common domain models) to other repos?
Basically the Go philosophy that a little bit of copying is better than a lot of dependency?
Some projects are also developed in the monorepo and exported via Copybara.
My team also uses it to version Starlark rule sets internally.
The key part for Copybara is that Google will make changes to the OSS projects from within the internal repo and everyone else will make changes to the OSS projects.
Having a public repo as a dependency for your private corporate repo is a pain in the ass development-wise. Having a tree of such dependencies is a migraine.
Say, to rebase upstream MySQL changes onto a fork in the monorepo (in a random, non-specific example)
https://josh-project.dev
The blog post from the Rust people:
https://blog.rust-lang.org/inside-rust/2026/06/04/how-josh-h...
Meta used to have an open source tool called fbshipit. But according to its open source repo they no longer use it:
https://github.com/facebookarchive/fbshipit
Any others in this space?
My shell script definitely wasn't google scale tho!
For example altering commit author emails during sync
I’m curious what downsides folks have experienced with this tool?
Any tips?
I had used those to create separate repo for website artifacts while the same also remain plugged into the webapp dev repo. (Both sides remain modifiable and changes mergeable to the other side.)
Thx.
It works great and I've seen many teams gain significant productivity when collaborating in a monorepo with public bits.
If you're even toying with an internal monorepo you owe it to yourself to give it a try.