Update MODULE.bazel.lock file as part of Copybara workflow

[guw]

We are using copybara this to push a set of common Bazel files into several other repositories. Some updates require updating the lock file in each of these destinations. We use git.github_pr_destination to push all modifications as single PR. Ideally the lock file update could be included there, i.e. something like a "bazel run" transformation would be nice. I couldn't find a way to do it in the examples/docs.

At minimum, I would like to run bazel mod deps to update the MODULE.bazel.lock file. A bonus would allowing me to run an arbitrary Bazel target (eg., bazel run //foo) as part of after_migration.

[farioas]

We’re also interested in having an execution hook as part of after_migration, for example to regenerate uv.lock using public dependencies instead of private ones.

[farioas]

@mikelalcon
Sorry for mentioning you directly - as the core owner, could you help with this?

[mikelalcon]

Hi!

I don't actively work in the project anymore. @hsudhof @joshgoldman-google would be better for this.

AFAIK there are no general scripting execution hook for after the migration. This is on purpose, as we want to avoid people not using Copybara transformations (that are reversible, etc.) and putting it in a script instead.

Having said that, we have a undocumented flag in git origin for doing something similar https://github.com/google/copybara/blob/master/java/com/google/copybara/git/GitOriginOptions.java#L34 . As the documentation in the flag says, it is not recommended to use and not guaranteed that will work in the future.

[guw]

In the case of lock file updates "reversibility" often requires re-running the tool after restoring the previous input files. Thus, a hook could account for that. But isn't Git providing the reversibility?

[farioas]

We’re also interested in having an execution hook as part of after_migration, for example to regenerate uv.lock using public dependencies instead of private ones.

--git-origin-checkout-hook worked for my use case. After checkout, I can regenerate uv.lock to remove internal dependencies before pushing to the public repository.