Do we need to fetch the complete git history?

[chances]

Describe the bug
Checking out existing branch fails in my CI workflow.

To Reproduce
My workflow file: https://github.com/chances/descartes-d/actions/runs/477666176/workflow

Failing CI build: https://github.com/chances/descartes-d/pull/2/checks?check_run_id=1681534009

Expected behavior
Your license year task is skipped because the license/2021 branch already exists with license updates.

Screenshots
N/A

Additional context
Failing CI build: https://github.com/chances/descartes-d/pull/2/checks?check_run_id=1681534009

[github-actions]

Hi there and welcome to this repository!

A maintainer will be with you shortly, but first and foremost I would like to thank you for taking the time to report this issue. Quality is of the highest priority for us, and we would never release anything with known defects. We aim to do our best but unfortunately you are here because you encountered something we didn't expect. Lets see if we can figure out what went wrong and provide a remedy for it.

[FantasticFiasco]

Hi @chances!

I think replacing

- uses: actions/checkout@v2

with

- uses: actions/checkout@v2
  with:
    fetch-depth: 0

should fix your problem. Can you try it out and report back?

[chances]

@FantasticFiasco Hm, that seems to resolve it.

Why is fetch-depth: 0 required?

[FantasticFiasco]

It seems that actions/checkout@v2, due to an optimization, only gets the lates commit by default. That operation will not get the tags, nor the branches of the repository. I can understand their decision, because most often in CI you only get the files to run the tests or what not, but we need more of the repo, and its history, thus the necessity to set fetch-depth: 0.

You can read more about their reasoning here.

[chances]

Other GitHub actions that play with Git don't require this flag on the checkout action, e.g. crazy-max/ghaction-github-pages@v2.

Can your action not workaround it like these other actions?

[FantasticFiasco]

crazy-max/ghaction-github-pages@v2 and this action doesn't share the same behaviour, thus you cannot compare them.

Where we in this action run git operations on the same repository checked out by the preceding actions/checkout@v2, crazy-max/ghaction-github-pages@v2 doesn't. They clone the specific branch of the target repository into a temp directory, and doesn't do any changes at all in the source repository that was checked out by their preceding actions/checkout@v2.

I'm quite sure that you could have found that out by comparing the source code in this repo with the source code in their repo. So let me turn the table. If removing fetch-depth: 0 is important to you, I challenge you to find a solution where we don't have to specify it using this action, and still remain with the same functionality.

[chances]

I'm well aware of the actions' differing behavior. My intention in bringing up the crazy-max/ghaction-github-pages action was with regard to its implicit recognition of the fetch depth optimization.

The fetch-depth requirement your action imposes wastes CI resources. The optimization is important, especially for large repos with heavy branch churn.

Your action could, instead of expecting the entire history of the target repo, git fetch the branch refs of interest.

[FantasticFiasco]

You are correct, the change would be for a better one. One could play around with fetch depth, one could also remove the dependency towards actions/checkout@v2 altogether and clone the repo ourselves.

I'll leave the issue open. Let's see if it gets some traction.

[FantasticFiasco]

I've come to the conclusion that depending on composability, where we depend on actions/checkout@v3, isn't a bad thing.

Closing issue.