[ci] r-configure comment job fails if PR branch is from a fork

[jameslamb]

Description

When the CI job that updates R-package/configure is triggered for a pull request from a fork, it fails with an error like the following:

Fetching the repository
  /usr/bin/git -c protocol.version=2 fetch --no-tags --prune --progress --no-recurse-submodules --depth=5 origin +refs/heads/linear-threading:refs/remotes/origin/linear-threading
  Error: fatal: couldn't find remote ref refs/heads/linear-threading
  The process '/usr/bin/git' failed with exit code 128
  Waiting 12 seconds before trying again
  /usr/bin/git -c protocol.version=2 fetch --no-tags --prune --progress --no-recurse-submodules --depth=5 origin +refs/heads/linear-threading:refs/remotes/origin/linear-threading
  Error: fatal: couldn't find remote ref refs/heads/linear-threading
  The process '/usr/bin/git' failed with exit code 128
  Waiting 19 seconds before trying again
  /usr/bin/git -c protocol.version=2 fetch --no-tags --prune --progress --no-recurse-submodules --depth=5 origin +refs/heads/linear-threading:refs/remotes/origin/linear-threading
  Error: fatal: couldn't find remote ref refs/heads/linear-threading
  Error: The process '/usr/bin/git' failed with exit code 128

This error happens during the Checkout Repository step.

https://github.com/microsoft/LightGBM/blob/44fe591a60d7427d64997c37b22768a92c97c47b/.github/workflows/r_configure.yml#L23-L31

Reproducible example

First observed this on #5368, see https://github.com/microsoft/LightGBM/pull/5368#issuecomment-1183359780.

I believe commenting /gha run r-configure on any PR from a fork will result in this issue.

Environment info

Latest commit as of July 13, 2022 (https://github.com/microsoft/LightGBM/commit/44fe591a60d7427d64997c37b22768a92c97c47b).

Notes

I'm actually not sure if it's even possible to make this work for PRs from forks, since this job needs to push a commit to the PR branch. I don't know if it's actually permitted by GitHub for this repo's CI to push to a branch on a fork.

[jameslamb]

don't know if it's permitted....for this repo's CI to push to ... a fork

Here's one report where someone claims it's possible: https://github.com/actions/checkout/issues/455#issuecomment-1079943559.

Using the pull_request_target condition.

And according to https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#running-your-workflow-based-on-files-changed-in-a-pull-request-1, it seems like it might be possible to automatically re-generate configure on any PR modifying configure.ac.

Like this:

on:
  pull_request_target:
    types:
      - opened
      - edited
    paths:
      - 'R-package/configure.ac'

[StrikerRUS]

I don't know if it's actually permitted by GitHub for this repo's CI to push to a branch on a fork.

As of time of creating r_configure.yml it wasn't possible, as I remember.

Using the pull_request_target condition.

Hmmm, sounds interesting...

[jameslamb]

I'm going to close this, so we can focus on other things.

It's easy enough to just regenerate the configure script with docker locally in the rare case where a PR from a fork requires it: https://github.com/microsoft/LightGBM/tree/master/R-package#changing-the-cran-package

[github-actions[bot]]

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