prepare-commit-msg

#!/bin/sh
# The first comments out the "Conflicts:" part of a merge commit.
# The second creates a template for a commit message
# The third example adds a Signed-off-by line to the message, that can
# still be edited.  This is rarely a good idea.

# This hook is invoked by git commit right after preparing the default log
# message, and before the editor is started.
# It takes one to three parameters. The first is the name of the file that
# contains the commit log message. The second is the source of the commit
# message, and can be: message (if a -m or -F option was given); template (if a
# -t option was given or the configuration option commit.template is set);
# merge (if the commit is a merge or a .git/MERGE_MSG file exists); squash (if
# a .git/SQUASH_MSG file exists); or commit, followed by a commit SHA1 (if a
# -c, -C or --amend option was given).
# If the exit status is non-zero, git commit will abort.
# The purpose of the hook is to edit the message file in place, and it is not
# suppressed by the --no-verify option. A non-zero exit means a failure of the
# hook and aborts the commit. It should not be used as replacement for
# pre-commit hook.
# The sample prepare-commit-msg hook that comes with git comments out the
# Conflicts: part of a merge's commit message.

>&2 echo "File: '$1' Source: '$2' Commit: '$3'"
>&2 echo "Environment:"
_git_vars=$( env | grep GIT )
>&2 echo "$_git_vars"
>&2 echo "#######################"
>&2 cat "$1"
>&2 echo "#######################"

case "$2,$3" in
  #merge,)
  #  /usr/bin/perl -i.bak -ne 's/^/# /, s/^# #/#/ if /^Conflicts/ .. /#/; print' "$1" ;;

  # During a git commit --amend:
  commit,HEAD)
        /usr/bin/perl -i.bak -nE '
        BEGIN { $source = $ENV{XSOURCE}; $sha = $ENV{XSHA} };
        if (!$first_line++) {
            say "## [MODULE] Declarative purpose of change";
            say "#2345678901234567890123456789012345678901234567890123456789|";
            print;
        }
        elsif (/^# Please enter the commit message for your changes/) {
            say "######################### AMENDING #########################";
            say "#   $_" for split("\n", `git diff HEAD^ --stat`);
            say "######################### THE DIFF #########################";
            say "#   $_" for split("\n", `git diff HEAD^`);
            say "############################################################";
            print;
        }
        else {
            print;
        }
        ' "$1" ;;

  # During a squash
  message,)
        /usr/bin/perl -i.bak -nE '
        BEGIN { $source = $ENV{XSOURCE}; $sha = $ENV{XSHA} };
        if (/^# The first commit/) {
            print;
            say "## [MODULE] Declarative purpose of change";
            say "#2345678901234567890123456789012345678901234567890123456789|";
        }
        elsif (/^# Please enter the commit message for your changes/) {
            say "######################## SQUASHING #########################";
            say "#   $_" for split("\n", `git diff HEAD^ --stat`);
            say "######################### THE DIFF #########################";
            say "#   $_" for split("\n", `git diff HEAD^`);
            say "############################################################";
            print;
        }
        else {
            print;
        }
        ' "$1" ;;

  # During a standard git commit, or during a commit "edit"
  ,|template,)
        splitting_commit=$( grep "You are currently splitting a commit while rebasing" "$1" )
        SPLITTING="$splitting_commit" /usr/bin/perl -i.bak -nE '
        BEGIN { $source = $ENV{XSOURCE}; $sha = $ENV{XSHA}; $printed = 0 }
        if (!$first_line++) {
            say "## [MODULE] Declarative purpose of change";
            say "#2345678901234567890123456789012345678901234567890123456789|";
            if ($ENV{SPLITTING}) {
                say "# Original message:";
                say for split("\n", `git show -s --format="%B" ORIG_HEAD`);
            } else {
                say "";
                say "## Nicer longer description of the context of the change, if";
                say "## needed/warranted by the change; or no_diff";
            }
            say "";
            say "######################## COMMITTING ########################";
            say "#   $_" for split("\n", `git diff --cached --stat`);
            say "######################### THE DIFF #########################";
            say "#   $_" for split("\n", `git diff --cached`);
            print "# $_";
        } else { print }
        ' "$1" ;;

  *)
      >&2 echo "prepare-commit-message had '$2,$3'"
      ;;
esac

# SOB=$(git var GIT_AUTHOR_IDENT | sed -n 's/^\(.*>\).*$/Signed-off-by: \1/p')
# grep -qs "^$SOB" "$1" || echo "$SOB" >> "$1"