threads / discuss / 46390

[FEATURE] git-commit option to prepend filename to commit message

Subject: [FEATURE] git-commit option to prepend filename to commit message

## tl;dr

3 messages between Jul 15, 2017 and Jul 15, 2017.

replies: 2people: 3as markdown or json

John J Foerch· Jul 15, 2017, 14:19 UTC · lore
Hello,
I had an idea for a feature for git commit that I wanted to pass along and see if maybe others would also think this would be useful.
Very often, I make commits that affect a single file, and have simple commit messages of this form:
    <filename>: <what changed>
The feature would be a command line option for git commit that would automatically prepend the "<filename>: " to the commit message.  The different cases of its behavior could be:
 - commit affecting a single file, with commit message given by -m:
   : prepend "<filename>: " to the message given by -m
 - commit affecting a single file, with commit message from editor:
   : pre-fill commit message template with "<filename>: "
 - commit affecting multiple files:
   : use common base directory of all affected files for <filename>, behaviors as above for use with -m or editor.
Anybody think that this or something like it would be a good convenience?
Thank you,
John Foerch
Johannes Sixt· Jul 15, 2017, 16:01 UTC · re: John J Foerch · lore

Re: [FEATURE] git-commit option to prepend filename to commit message

Am 15.07.2017 um 16:19 schrieb John J Foerch:
> The feature would be a command line option for git commit that would
> automatically prepend the "<filename>: " to the commit message.
Write a prepare-commit-msg hook:
https://www.kernel.org/pub/software/scm/git/docs/githooks.html#_prepare_commit_msg
-- Hannes
Jeff King· Jul 15, 2017, 16:05 UTC · re: John J Foerch · lore

Re: [FEATURE] git-commit option to prepend filename to commit message

On Sat, Jul 15, 2017 at 10:19:34AM -0400, John J Foerch wrote:
Show 17 quoted lines
> The feature would be a command line option for git commit that would
> automatically prepend the "<filename>: " to the commit message.  The
> different cases of its behavior could be:
> 
>  - commit affecting a single file, with commit message given by -m:
> 
>    : prepend "<filename>: " to the message given by -m
> 
>  - commit affecting a single file, with commit message from editor:
> 
>    : pre-fill commit message template with "<filename>: "
> 
>  - commit affecting multiple files:
> 
>    : use common base directory of all affected files for <filename>, behaviors as above for use with -m or editor.
> 
> Anybody think that this or something like it would be a good convenience?

Johannes already pointed you to the prepare-commit-msg hook, which I think is the right solution. I wrote a rough sketch for fun (note that you could write it in whatever language you like if the mix of perl/shell isn't to your liking):

-- >8 -- #!/bin/sh

# only kick in for vanilla commit, or "-m" case "$2" in ""|message) ;; *) exit 0 esac

# common prefix of all changed files
prefix=$(
        git diff-index --name-only HEAD |
        perl -lne '
                if (!defined $prefix) {
                        $prefix = $_;
                } else {
                        chop $prefix while !/^\Q$prefix\E/;
                }
                END {
                        # trim trailing slash if present
                        $prefix =~ s{/$}{};
                        print $prefix
                }
        '
)
# now stick the prefix at the start of the message-in-progress
{
        printf '%s' "$prefix: "
        cat "$1"
} >"$1".tmp &&
mv "$1".tmp "$1"

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