Determine the first and last commit date for each user in a git repo.

git_user_date_range.py

import datetime
from collections import defaultdict
import subprocess

def main():
    git_log = subprocess.check_output(['git', 'log', "--pretty=format:%an\t%ct"])

    users = defaultdict(list)
    for line in git_log.split('\n'):
        name, commit_time = line.strip().split('\t')
        commit_time = datetime.datetime.fromtimestamp(int(commit_time))

        users[name].append(commit_time)

    print '\t'.join(('User', 'First Commit', 'Last Commit', 'Count'))
    for name, dates in sorted(users.iteritems(), key=lambda x:x[0]):
        start, end = min(dates), max(dates)

        parts = (name, start, end, len(dates))
        print '\t'.join(str(s) for s in parts)

if __name__ == '__main__':
    main()