Merge branch 'sa/cat-file-mailmap'

"git cat-file" learned an option to use the mailmap when showing commit and tag objects. * sa/cat-file-mailmap: cat-file: add mailmap support ident: rename commit_rewrite_person() to apply_mailmap_to_header() ident: move commit_rewrite_person() to ident.c revision: improve commit_rewrite_person()