Expose prepare-commit-msg arguments as environment vars

[M-Whitaker]

Closes #2406.

This adds the ability to pass environ args that are not files to the prepare-commit-msg hook as defined by the git specification:

Git hook documentation

If you want some tests for this more than happy to think up some, however, I have tried to only add to existing code and use optional arguments so all existing tests are not affected.

[asottile]

so it shouldn't treat them as arguments, pre-commit only deals in files

they should be environment variables to match up with the other hooks

[M-Whitaker]

Ah! I see what you mean now...

so it shouldn't treat them as arguments, pre-commit only deals in files

they should be environment variables to match up with the other hooks

I have changed it accordingly.

[M-Whitaker]

This was the most elegant way I thought of to keep this underneath the PEP8 line length. Maybe you have an opinion on this...

if args.prepare_commit_message_source:
         environ['PRE_COMMIT_COMMIT_MSG_SOURCE'] \
             = args.prepare_commit_message_source

I have implemented all the other name changes as you suggested.

In regards to the tests:

Do you usually extend the existing tests i.e. test_prepare_commit_msg_hook or do you want one for each different possible argument passed from the hook?

[asottile]

This was the most elegant way I thought of to keep this underneath the PEP8 line length. Maybe you have an opinion on this...

if args.prepare_commit_message_source:
         environ['PRE_COMMIT_COMMIT_MSG_SOURCE'] \
             = args.prepare_commit_message_source

I have implemented all the other name changes as you suggested.

In regards to the tests:

Do you usually extend the existing tests i.e. test_prepare_commit_msg_hook or do you want one for each different possible argument passed from the hook?

even pep8 suggests using parens over backslashes:

The preferred way of wrapping long lines is by using Python’s implied line continuation inside parentheses, brackets and braces.

and yeah there'll need to be new tests -- whatever is needed to demonstrate the change should be sufficient

[asottile]

[Konfekt]

Hello, is there any documentation in pre-commit on these environment vars?
I suspected a check for os.getenv("PRE_COMMIT_COMMIT_MSG_SOURCE") to work, but this is always None even when amending, say (see man 5 githooks).

[twistfire92]

Hello, is there any documentation in pre-commit on these environment vars? I suspected a check for os.getenv("PRE_COMMIT_COMMIT_MSG_SOURCE") to work, but this is always None even when amending, say (see man 5 githooks).

@asottile Same problem, but with PRE_COMMIT_COMMIT_OBJECT_NAME

@Konfekt did you resolve it?

[Konfekt]

Hello, I think I got interested in it for a commit message generation script and resorted to detecting rebases by detecting more than one command-line argument https://gist.github.com/Konfekt/d9640c390deea4beafcf74e29410b8a6#file-chatgpt-write-msg-py-L8 but actually cannot remember at all