Rewrite "am" in "C".
* pt/am-builtin: (46 commits)
git-am: add am.threeWay config variable
builtin-am: remove redirection to git-am.sh
builtin-am: check for valid committer ident
builtin-am: implement legacy -b/--binary option
builtin-am: implement -i/--interactive
builtin-am: support and auto-detect mercurial patches
builtin-am: support and auto-detect StGit series files
builtin-am: support and auto-detect StGit patches
builtin-am: rerere support
builtin-am: invoke post-applypatch hook
builtin-am: invoke pre-applypatch hook
builtin-am: invoke applypatch-msg hook
builtin-am: support automatic notes copying
builtin-am: invoke post-rewrite hook
builtin-am: implement -S/--gpg-sign, commit.gpgsign
builtin-am: implement --committer-date-is-author-date
builtin-am: implement --ignore-date
builtin-am: pass git-apply's options to git-apply
builtin-am: implement --[no-]scissors
builtin-am: support --keep-cr, am.keepcr
...