git-retimestamp

#!/usr/bin/env python

################################################################################
#
#   Description:
#   ------------
#       Resets the timestamps of all commits in the currently checked out branch
#       to the current time.
#
#       The only reason you'd want to do this is to ensure that GitHub displays
#       the commits in pull requests in the correct order (i.e. according to the
#       parent-child relationship of the commits and not according to the time
#       when a commit was originally made). As such, this is only relevant to
#       code that is hosted on GitHub. Moreover, this script would become
#       obsolete if GitHub one day stops making nonsensical statements about
#       git rebases altering the space-time continuum and instead just fixes its
#       code. For more information, refer to:
#       https://help.github.com/articles/why-are-my-commits-in-the-wrong-order/
#
#   Usage:
#   ------
#   (first place this script in one of the directories in $PATH)
#       $> cd path/to/your/repo
#       $> git retimestamp
#
################################################################################

import argparse
import git
import sys


################################################################################
#
#   Prints an error message and exits with an error status code
#
#   Params:
#       msg = message to be printed before exiting
#
################################################################################

def die(msg):
    print msg
    sys.exit(1)


################################################################################
#
#   Displays a list of commits that will be re-timestamped, so that the user can
#   confirm that the correct commits will be targeted
#
#   Params:
#       base = the base of the branch
#       branch_name = the name of the branch
#
#   Returns:
#       the number of commits in the branch, relative to the base of the branch
#
################################################################################

def display_commits_list(base, branch_name):
    commits_list = git.get_commits_list(base, branch_name)

    # Show the user how many (and which) commits will be modified
    num_commits = len(commits_list)

    if num_commits == 1:
        print "The timestamps of the following commit will be reset to the current time:"
    else:
        print "The timestamps of the following {} commits will be reset to the current time:".format(num_commits)

    commit_num = 0
    if num_commits > 9:
        # Show only the top and bottom 3 commits
        for commit in commits_list[0:3]:
            commit_num += 1
            commit_hash, commit_title = commit.split(' ', 1)
            sys.stdout.write('    ' + str(commit_num) + '. (\033[34m' +
                commit_hash + '\033[0m) ' + commit_title)

            if commit_num == 1:
                sys.stdout.write("    \033[32m<-- old HEAD of '" + branch_name +
                    "'\033[0m\n")
            else:
                sys.stdout.write('\n')

        print "    ..."
        print "    ... << {} more commits >> ...".format(num_commits - 6)
        print "    ..."

        commit_num = num_commits - 3
        for commit in commits_list[-3:]:
            commit_num += 1
            commit_hash, commit_title = commit.split(' ', 1)
            sys.stdout.write('    ' + str(commit_num) + '. (\033[34m' +
                commit_hash + '\033[0m) ' + commit_title + '\n')
    else:
        # Show all commits
        for commit in commits_list:
            commit_num += 1
            commit_hash, commit_title = commit.split(' ', 1)
            sys.stdout.write('    ' + str(commit_num) + '. (\033[34m' +
                commit_hash + '\033[0m) ' + commit_title)

            if commit_num == 1:
                sys.stdout.write("    \033[32m<-- old HEAD of '" + branch_name +
                    "'\033[0m\n")
            else:
                sys.stdout.write('\n')

    return num_commits

# Set up command line arguments
parser = argparse.ArgumentParser(usage='%(prog)s [ARGUMENTS]',
    description='Set timestamps of all commits in a branch to the current time')
parser.add_argument('-b', '--base', default='upstream/master',
    help='branch (or git ref) to use as the base of the branch '
        "(defaults to 'upstream/master')")
args = vars(parser.parse_args())

if not git.in_repo():
    die("Not a git repository. Aborting")

if not git.is_valid_commit(args['base']):
    die("Invalid base '{}'. Aborting.".format(args['base']))

branch_name = git.get_current_branch()
if not branch_name:
    die("No branch is currently checked out. Aborting.")

num_commits = display_commits_list(args['base'], branch_name)

# Ask for confirmation
proceed = raw_input("Proceed (y/n)? ")
if proceed != 'y' and proceed != 'Y':
    die("Aborting.")

if git.is_gpg_signing_enabled():
    author_email = git.get_user_email()
    if not author_email:
        die("Failed to get the author email address. Aborting.")

    gpg_sign_argument = '--gpg-sign=' + author_email
else:
    gpg_sign_argument = ''

commits_range_argument = 'HEAD~' + str(num_commits)

# Perform the actual resetting of the timestamps
try:
    if gpg_sign_argument:
        git.run_command('rebase', '--ignore-date', gpg_sign_argument,
            commits_range_argument)
    else:
        git.run_command('rebase', '--ignore-date', commits_range_argument)
except git.GitException as e:
    print "Git command '{}' failed with the following error:".format(e.args[0])
    die(e.args[1].rstrip('\n'))

print "Re-timestamp complete."

# vim: set tw=80 :