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

Calling exec < /dev/tty assigns standard input to the keyboard. Works for me in a post-commit git hook:

#!/bin/sh

echo "[post-commit hook] Commit done!"

# Allows us to read user input below, assigns stdin to keyboard
exec < /dev/tty

while true; do
  read -p "[post-commit hook] Check for outdated gems? (Y/n) " yn
  if [ "$yn" = "" ]; then
    yn='Y'
  fi
  case $yn in
      [Yy] ) bundle outdated --pre; break;;
      [Nn] ) exit;;
      * ) echo "Please answer y or n for yes or no.";;
  esac
done