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. It is
based on my finished prototype of the rewrite[1], and over the next 5 weeks I
will be cutting out small patches from the prototype to make it easier to
review and refine the patch series.
This is part of my GSoC project to rewrite git-pull.sh into git-am.sh into C
builtins[2].
A small benchmark that applies 50 patches[3]:
#!/bin/sh
git init &&
echo initial >file &&
git add file &&
git commit -m initial &&
git branch before-am &&
for x in $(seq 50)
do
echo $x >>file &&
git commit -a -m $x
done &&
git format-patch --stdout before-am.. >patches &&
git checkout before-am &&
time git patches >/dev/null
I ran this benchmark on my *Linux* system.
Timings for git on master:
1.40s, 1.42s, 1.25s, 1.32s, 1.10s. Avg: ~1.30s
Timings for git on master + this patch series applied:
0.24s, 0.22s, 0.22s, 0.19s, 0.25s. Avg: ~0.22s
This is around a 6x speedup. It's not because this patch series does less than
git-am.sh -- similar speedups can be observed with the prototype, which passes
the test suite[4].
(Sorry for leaving the other reviews hanging. I was too preoccupied with the
git-am rewrite, and was afraid of forgetting important details should I context
switch. Now that the prototype is finished I can deal with the other patch
series'.)
[1] https://github.com/pyokagan/git/compare/master...pyokagan:pt/ref-builtin-am
[2] https://gist.github.com/pyokagan/1b7b0d1f4dab6ba3cef1
[3] Since a 56-patch series was posted recently ;-)
[4] The subset of the test suite that calls git-rebase and git-am.
Paul Tan (8):
wrapper: implement xopen()
wrapper: implement xfopen()
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
Makefile | 2 +-
builtin.h | 1 +
builtin/am.c | 687 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
git-compat-util.h | 2 +
git.c | 1 +
wrapper.c | 37 +++
6 files changed, 729 insertions(+), 1 deletion(-)
create mode 100644 builtin/am.c
--
2.1.4
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