Re: New Git hooks for checking file names in commit messages

[Jim Porter <jporterbugs@gmail.com>]

On 4/21/2023 6:57 AM, Alan Mackenzie wrote:
> How is this helpful?  Telling somebody they've made a mistake is only
> helpful if they can correct it.  If "it's too late to error out", it
> will just create annoyance.  Immediately after such a commit it is
> possible to use $ git commit --amend, but not later.

This is why I added a post-commit hook that informs the committer of the 
problem immediately after committing. However, since this is a 
*post*-commit hook, it's too late to abort the commit. So there is a 
message, but it's purely advisory at that stage. Sorry if my wording was 
unclear originally.

>> [1] It's hard to do this during the commit-msg hook since there's no
>> cross-platform way I know of to handle amending commits properly.
> 
> I don't understand this bit.  Why does the lack of a way of amending
> commits make it difficult to error out from the commit-msg hook?  What
> am I missing?

It's impossible (as far as I'm aware) to reliably get a list of changed 
files from Git during the commit-msg hook. Since you can't tell whether 
the commit is being amended without platform-specific hacks, you have no 
way of knowing whether you should compute your diff against HEAD or HEAD^.