Merge branch 'jk/commit-author-parsing'

Code clean-up. * jk/commit-author-parsing: determine_author_info(): copy getenv output determine_author_info(): reuse parsing functions date: use strbufs in date-formatting functions record_author_date(): use find_commit_header() record_author_date(): fix memory leak on malformed commit commit: provide a function to find a header in a buffer