Support multiple flake directories

[lucperkins]

We like the idea behind #98 but unfortunately we switched this Action to use JS instead of Bash, which means that implementing that would be a non-trivial amount of work for @DavHau so I've decided to go ahead and implement it on my own (given that I know our internal libs well).

[lucperkins]

@DavHau If you could give this a try in one of your repos, that would be great!

- uses: DeterminateSystems/update-flake-lock@multiple-flake-dirs-ts

[DavHau]

Thanks for this. Will test it tomorrow

[lucperkins]

I've tested this out in an external repo: https://github.com/lucperkins/update-flake-lock-multiple-dirs

This run successfully created this PR (with sub-dirs subflake1 and subflake2).

There were two unsuccessful runs of the same workflow but that was solely related to improper permissions on the test repo. Changing the permissions resolved the issue.

[cole-h]

According to your test run, functionality seems to work just fine, but I'm a bit worried about UX.

• The PR body only lists one of the updated flake.locks.
  • I'd expect it to either list all of them, or none of them.
• The commit messages are all just flake.lock: Update, but flake.lock is only updated once -- the others that are updated are subflake1/flake.lock and subflake2/flake.lock. However, if I manually put a flake.nix and flake.lock in some subdir in a local repo of mine and run nix flake update --commit-lock-file, it correctly commits it as subdir/flake.lock: Update

[lucperkins]

@cole-h The root flake.lock is only updated once because I added it after the two sub-dirs. As for the PR body, we are a bit constrained here by Actions' inputs (in this case the pr-body input). Those can't be dynamic and the best we can do is update the default value.

Update: okay, I see now that we have some flexibility with the templating so I'll update the pr-body default to be more descriptive.

[cole-h]

Yes, I know the root flake.lock is only updated once. However, if you look at your PR, the commit messages all say flake.lock: Update:

Whereas using nix flake update --commit-lock-file in a subdirectory will give you path/to/the/flake.lock: Update as the commit message.

This doesn't strike me as good UX, not being able to distinguish between which commit updated which flake.lock....