[PATCH/WIP v3 00/31] Make git-am a builtin

This patch series depends on pt/pull-builtin for OPT_PASSTHRU_ARGV() and argv_array_pushv().

This is a re-roll of [WIP v3]. Thanks Junio and Stefan for the reviews last round.

The biggest addition this round would be the support for git-rebase. Here's a small unscientific benchmark that rebases 50 patches:

	git init &&
	echo initial >file &&
	git add file &&
	git commit -m initial &&
	git tag initial &&
	for x in $(seq 50)
	do
	    echo $x >>file &&
	    git commit -a -m $x
	done &&
	git checkout -b onto-rebase initial &&
	git commit --allow-empty -mempty &&
	time git rebase -q --onto onto-rebase initial master

With master:

1.53s, 1.55s, 1.17s, 1.52s, 1.22s. Avg: ~1.40s

With master + this patch series:

0.22s, 0.22s, 0.18s, 0.21s, 0.18s. Avg: ~0.20s

So this is around a 6-7x speedup.

Previous versions:

[WIP v1] http://thread.gmane.org/gmane.comp.version-control.git/270048 [WIP v2] http://thread.gmane.org/gmane.comp.version-control.git/271381

git-am is a commonly used command for applying a series of patches from a mailbox to the current branch. Currently, it is implemented by the shell script git-am.sh. However, compared to C, shell scripts have certain deficiencies: they need to spawn a lot of processes, introduce a lot of dependencies and cannot take advantage of git's internal caches.

This WIP patch series rewrites git-am.sh into optimized C builtin/am.c, and is part of my GSoC project to rewrite git-pull and git-am into C builtins[1].

[1] https://gist.github.com/pyokagan/1b7b0d1f4dab6ba3cef1

Paul Tan (31):
  wrapper: implement xopen()
  wrapper: implement xfopen()
  am: implement skeletal builtin am
  am: implement patch queue mechanism
  am: split out mbox/maildir patches with git-mailsplit
  am: detect mbox patches
  am: extract patch, message and authorship with git-mailinfo
  am: apply patch with git-apply
  am: commit applied patch
  am: refresh the index at start
  am: refuse to apply patches if index is dirty
  am: implement --resolved/--continue
  am: implement --skip
  am: implement --abort
  am: don't accept patches when there's a session in progress
  am: implement quiet option
  am: exit with user friendly message on patch failure
  am: implement am --signoff
  cache-tree: introduce write_index_as_tree()
  am: implement 3-way merge
  am: --rebasing
  am: don't use git-mailinfo if --rebasing
  am: handle stray state directory
  am: implement -k/--keep, --keep-non-patch
  am: implement --[no-]message-id, am.messageid
  am: support --keep-cr, am.keepcr
  am: implement --[no-]scissors
  am: pass git-apply's options to git-apply
  am: implement --ignore-date
  am: implement --committer-date-is-author-date
  am: implement -S/--gpg-sign, commit.gpgsign

 Makefile          |    1 +
 builtin.h         |    1 +
 builtin/am.c      | 1650 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 cache-tree.c      |   29 +-
 cache-tree.h      |    1 +
 git-compat-util.h |    2 +
 git.c             |    1 +
 wrapper.c         |   43 ++
 8 files changed, 1716 insertions(+), 12 deletions(-)
 create mode 100644 builtin/am.c