Add a workflow to synchronize refs from git/git to gitgitgadget/git

[dscho]

The idea is, of course, to act on the push webhook that dutifully pings GitGitGadget's GitHub App every time a ref is pushed to git/git, and to let the App trigger this shiny new workflow to do the honors of keeping gitgitgadget/git up to date.

That change to the GitHub App will have to be implemented, still, but first this here PR needs to be reviewed and merged because GitHub workflows can only be triggered by workflow_dispatch events if their definitions are on the main branch.

[webstech]

A couple of other thoughts.

• Should the source/target repos be allowed as inputs? Thinking of being able to test with any repo. That may be a problem with the auth stuff so is there anything there that could use a PAT if it was supplied?
• If this was to be a model for another user of ggg, are there other things that need to be more flexible? Repo only has main branch is one consideration. Maybe not all that important until someone wants to use it as a model.

[dscho]

• Should the source/target repos be allowed as inputs? Thinking of being able to test with any repo. That may be a problem with the auth stuff so is there anything there that could use a PAT if it was supplied?

I was considering this, but it looks as if this would rather complicate the code, and it is already more complicated than I had wished.

• If this was to be a model for another user of ggg, are there other things that need to be more flexible? Repo only has main branch is one consideration. Maybe not all that important until someone wants to use it as a model.

Valid concern! However, this is something we need to tackle on the GitHub App side, which is expected to trigger this workflow.

[dscho]

@webstech thank you for your review! I pushed an updated version (addressing all suggestions except the reusable workflows one).

[webstech]

Wouldn't the rest of the code be included in this if? ie, no fetch, so no push?

[webstech]

@dscho Did you miss this or was I mistaken?

[dscho]

Oh, sorry, I missed your comment.

No, the rest of the code still needs to run: the workflow could be triggered by a deletion, in which case source-sha would be empty.

[webstech]

the workflow could be triggered by a deletion, in which case source-sha would be empty.

TIL on a push, an empty <src> in the refspec will delete the <dst> ref. Good to know.

[webstech]

• Should the source/target repos be allowed as inputs? Thinking of being able to test with any repo. That may be a problem with the auth stuff so is there anything there that could use a PAT if it was supplied?

I was considering this, but it looks as if this would rather complicate the code, and it is already more complicated than I had wished.

Wouldn't it be the same as refs (with more inputs specified)?

  SOURCE_REPOSITORY: ${{ inputs.source || 'git/git' }}
  TARGET_REPOSITORY: ${{ inputs.target || 'gitgitgadget/git' }}

Still thinking about how to have test runs against my own mock repos. It can wait if you want since the PAT support would also be needed.

[dscho]

I guess we could make those workflow inputs (with the current values in the env block via || "yaddayadda"), and then you can simply temporarily install the gitgitgadget app on your repository for testing... (you'd also need to fork -workflows and push this PR branch to your main because workflow_dispatch only works if it exists on the main branch.)

[dscho]

we could make those workflow inputs

@webstech I've now done that.