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git/Documentation/git-apply.txt
Eric W. Biederman 4749588713 Implement limited context matching in git-apply.
Ok this really should be the good version.  The option
handling has been reworked to be automation safe.

Currently to import the -mm tree I have to work around
git-apply by using patch.  Because some of Andrews
patches in quilt will only apply with fuzz.

I started out implementing a --fuzz option and then I realized
fuzz is not a very safe concept for an automated system.  What
you really want is a minimum number of context lines that must
match.  This allows policy to be set without knowing how many
lines of context a patch actually provides.   By default
the policy remains to match all provided lines of context.

Allowng git-apply to match a restricted set of context makes
it much easier to import the -mm tree into git.  I am still only
processing  1.5 to 1.6 patches a second for the 692 patches in
2.6.17-rc1-mm2 is still painful but it does help.

If I just loop through all of Andrews patches in order
and run git-apply --index -C1 I process the entire patchset
in 1m53s or about 6 patches per second.  So running
git-mailinfo, git-write-tree, git-commit-tree, and
git-update-ref everytime has a measurable impact,
and shows things can be speeded up even more.

All of these timings were taking on my poor 700Mhz Athlon
with 512MB of ram.  So people with fast machiens should
see much better performance.

When a match is found after the number of context are reduced a
warning is generated.  Since this is a rare event and possibly
dangerous this seems to make sense.  Unless you are patching
a single file the error message is a little bit terse at
the moment, but it should be easy to go back and fix.

I have also updated the documentation for git-apply to reflect
the new -C option that sets the minimum number of context
lines that must match.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>
2006-04-10 19:44:08 -07:00

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git-apply(1)
============
NAME
----
git-apply - Apply patch on a git index file and a work tree
SYNOPSIS
--------
[verse]
'git-apply' [--stat] [--numstat] [--summary] [--check] [--index] [--apply]
[--no-add] [--index-info] [--allow-binary-replacement] [-z] [-pNUM]
[-CNUM] [--whitespace=<nowarn|warn|error|error-all|strip>]
[<patch>...]
DESCRIPTION
-----------
Reads supplied diff output and applies it on a git index file
and a work tree.
OPTIONS
-------
<patch>...::
The files to read patch from. '-' can be used to read
from the standard input.
--stat::
Instead of applying the patch, output diffstat for the
input. Turns off "apply".
--numstat::
Similar to \--stat, but shows number of added and
deleted lines in decimal notation and pathname without
abbreviation, to make it more machine friendly. Turns
off "apply".
--summary::
Instead of applying the patch, output a condensed
summary of information obtained from git diff extended
headers, such as creations, renames and mode changes.
Turns off "apply".
--check::
Instead of applying the patch, see if the patch is
applicable to the current work tree and/or the index
file and detects errors. Turns off "apply".
--index::
When --check is in effect, or when applying the patch
(which is the default when none of the options that
disables it is in effect), make sure the patch is
applicable to what the current index file records. If
the file to be patched in the work tree is not
up-to-date, it is flagged as an error. This flag also
causes the index file to be updated.
--index-info::
Newer git-diff output has embedded 'index information'
for each blob to help identify the original version that
the patch applies to. When this flag is given, and if
the original version of the blob is available locally,
outputs information about them to the standard output.
-z::
When showing the index information, do not munge paths,
but use NUL terminated machine readable format. Without
this flag, the pathnames output will have TAB, LF, and
backslash characters replaced with `\t`, `\n`, and `\\`,
respectively.
-p<n>::
Remove <n> leading slashes from traditional diff paths. The
default is 1.
-C<n>::
Ensure at least <n> lines of surrounding context match before
and after each change. When fewer lines of surrounding
context exist they all most match. By default no context is
ever ignored.
--apply::
If you use any of the options marked ``Turns off
"apply"'' above, git-apply reads and outputs the
information you asked without actually applying the
patch. Give this flag after those flags to also apply
the patch.
--no-add::
When applying a patch, ignore additions made by the
patch. This can be used to extract common part between
two files by first running `diff` on them and applying
the result with this option, which would apply the
deletion part but not addition part.
--allow-binary-replacement::
When applying a patch, which is a git-enhanced patch
that was prepared to record the pre- and post-image object
name in full, and the path being patched exactly matches
the object the patch applies to (i.e. "index" line's
pre-image object name is what is in the working tree),
and the post-image object is available in the object
database, use the post-image object as the patch
result. This allows binary files to be patched in a
very limited way.
--whitespace=<option>::
When applying a patch, detect a new or modified line
that ends with trailing whitespaces (this includes a
line that solely consists of whitespaces). By default,
the command outputs warning messages and applies the
patch.
When `git-apply` is used for statistics and not applying a
patch, it defaults to `nowarn`.
You can use different `<option>` to control this
behaviour:
+
* `nowarn` turns off the trailing whitespace warning.
* `warn` outputs warnings for a few such errors, but applies the
patch (default).
* `error` outputs warnings for a few such errors, and refuses
to apply the patch.
* `error-all` is similar to `error` but shows all errors.
* `strip` outputs warnings for a few such errors, strips out the
trailing whitespaces and applies the patch.
Configuration
-------------
apply.whitespace::
When no `--whitespace` flag is given from the command
line, this configuration item is used as the default.
Author
------
Written by Linus Torvalds <torvalds@osdl.org>
Documentation
--------------
Documentation by Junio C Hamano
GIT
---
Part of the gitlink:git[7] suite