How do I prompt the user from within a commit-msg hook?

Question

I want to warn the user if their commit message doesn't follow a certain set of guidelines, and then give them the option to edit their commit message, ignore the warning, or cancel the commit. The problem is that I don't seem to have access to stdin.

Below is my commit-msg file:

function verify_info {
    if [ -z "$(grep '$2:.*[a-zA-Z]' $1)" ]
    then
        echo >&2 $2 information should not be omitted
        local_editor=`git config --get core.editor`
        if [ -z "${local_editor}" ]
        then
            local_editor=${EDITOR}
        fi
        echo "Do you want to"
        select CHOICE in "edit the commit message" "ignore this warning" "cancel the commit"; do
            case ${CHOICE} in
                i*) echo "Warning ignored"
                    ;;
                e*) ${local_editor} $1
                    verify_info "$1" $2
                    ;;
                *)  echo "CHOICE = ${CHOICE}"
                    exit 1
                    ;;
            esac
        done
    fi
}

verify_info "$1" "Scope"
if [ $# -ne 0 ];
then
    exit $#
fi
verify_info "$1" "Affects"
if [ $# -ne 0 ];
then
    exit $#
fi

exit 0

Here is the output when I leave the Scope information blank:

Scope information should not be omitted
Do you want to:
1) edit the commit message  3) cancel the commit
2) ignore this warning
#?

The message is correct, but it doesn't actually stop for input. I've also tried using the simpler "read" command, and it has the same problem. It seems that the problem is that at this point git has control of stdin and is providing its own input. How do I fix this?

Update: It seems this might be a duplicate of this question which unfortunately seems to suggest I'm out of luck.

Answer 1

The commit-msg hook is not run in an interactive environment (as you have noticed).

The only way to reliable notify the user would be to write an error to stdout, place a copy of the commit message in a 'BAD_MSG' file and instruct the user to edit the file and 'git commit --file=BAD_MSG'

---

If you have some control over the environment you could have an alternate editor which is a wrapper script that checks the proposed message, and can restart the editor with an extra commented message.

Basically, you run the editor, check the file saved against your rules. and if it fails, prepend your warning message (with leading #) to the file and restart the editor.

You could even allow them to put in a '#FORCE=true' line in the message which would suppress the check and continue.