[Python] Make pre-commit work to check the commit message on GitHub

I am wondering how I can make a commit message pre-commit hook work in both locally and on GitHub using pre-commit.

We use pre-commit in two projects I am involved in to locally check that the commit message adheres to some standards through two Python scripts:

https://github.com/InsightSoftwareConsortium/ITK/blob/main/Utilities/Hooks/kw-commit-msg.py

and

https://github.com/dipy/dipy/pull/3589/files (still a PR)

And the corresponding .pre-commit-config.yaml hooks:

- id: kw-commit-msg
name: 'kw commit-msg'
entry: 'Utilities/Hooks/run-pixi-python.sh Utilities/Hooks/kw-commit-msg.py'
language: system
stages: [commit-msg]


and

- repo: local
hooks:
- id: dipy-commit-msg
name: 'dipy-commit-msg'
entry: 'tools/hooks/commit-msg.py'
language: python


I have realized that although the hook works well locally (as long as the stages: [commit-msg] is there), the check is not run on GitHub: https://github.com/dipy/dipy/actions/runs/16013005246/job/45174358635?pr=3589#step:4:110

I have done an additional quick test submitting a non-compliant message to a fork of mine on the other project as well and pre-commit checks pass: https://github.com/jhlegarreta/ITK/actions/runs/16332297568/job/46137422968?pr=1#step:5:150

As suggested by a colleague, if I remove stages: [commit-msg] from the .pre-commit-config.yaml file, the check is triggered on GitHub, but it fails even if the commit message is compliant:

https://github.com/dipy/dipy/actions/runs/16331696031/job/46135555136?pr=3589#step:4:119

and shows the error:

To continue editing a message, run the command:
git commit -e -F "/home/runner/work/dipy/dipy/.git/COMMIT_MSG"
(assuming your working directory is at the top).
Traceback (most recent call last):
File "/home/runner/work/dipy/dipy/tools/hooks/commit-msg.py", line 147, in <module>
main()
File "/home/runner/work/dipy/dipy/tools/hooks/commit-msg.py", line 81, in main
subject_line: str = input_file_lines[0]
IndexError: list index out of range


(the die message about how the commit should be formatted is also shown 3 times; not sure why)

It looks like the commit message file is not found by the CI runner because the commit is already made at that point.

So how can I make work the hook both locally and on GitHub?

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