compute-hash

#!/usr/bin/env python3

import os
import sys
import time
from hashlib import sha1
from fake_git import check_call, commit_metadata
from tempfile import TemporaryDirectory

os.environ['GIT_PAGER'] = ''

commit_message = 'Add foo'

def hash(object_type, contents):
    return sha1(b'%s %d\0%s' % (object_type, len(contents), contents))

file_hash = hash(b'blob', b'hi\n')
print(f'file_hash = {file_hash.hexdigest()}')

tree_hash = hash(b'tree', b'100644 foo\0%b' % file_hash.digest())
print(f'tree_hash = {tree_hash.hexdigest()}')

commit = """tree %s
author %s <%s> %s
committer %s <%s> %s

%s
""" % (tree_hash.hexdigest(),
    commit_metadata['name'], commit_metadata['email'], commit_metadata['date'],
    commit_metadata['name'], commit_metadata['email'], commit_metadata['date'],
    commit_message)
commit = commit.encode('UTF-8')

commit_hash = hash(b'commit', commit)
print(f'commit_hash = {commit_hash.hexdigest()}')
print()
sys.stdout.flush()

with TemporaryDirectory() as t:
    os.chdir(t)
    with open('foo', 'w') as f:
        f.write('hi\n')
    check_call(['git', 'init'])
    check_call(['git', 'add', 'foo'])

    check_call(['git', 'commit', '-m', commit_message])
    check_call(['git', 'log', '-m', 'foo'])