Display the number of additions and deletions per commit for a file

git_helper.py

#!/usr/bin/env python3

"""
Display the number of additions and deletions per commit for a file e.g.

    $ ./git_helper.py index.d.ts
    commit added deleted
    bd1de57 4	4	index.d.ts Error object fix
    c3a54db 25	120	index.d.ts Merge branch 'master' into types-2.0
    e9a0e98 58	10	index.d.ts Merge commit 'upstream/master~300' into merge_7_25
"""

import sys
import subprocess

file_path = sys.argv[1]  # e.g. 'index.d.ts'
command = 'git log --oneline --format="%h %s" {}'.format(file_path)
subproc = subprocess.Popen(command, shell=True, stdout=subprocess.PIPE)
commits = subproc.stdout.read().decode("utf-8")

commit_lines = commits.split('\n')[:-1]
hashes = []
messages = []
for entry in commit_lines:
    hashes.append(entry.split(' ')[0])
    messages.append(entry[8:])

print('commit added deleted')
for i, hash in enumerate(hashes):
    command = 'git diff --numstat {hash}~1 {hash} {file_path}'.format(hash=hash, file_path=file_path)
    subproc = subprocess.Popen(command, shell=True, stdout=subprocess.PIPE)
    changes = subproc.stdout.read().decode("utf-8")[:-1]
    print(hash + ' ' + changes + ' ' + messages[i])