Subject: Re: [PATCH] git apply: binary files differ can be applied with -pN (N>1).

From: Jiang Xin <[email-masked]>
Date: Thu, 25 Nov 2010 09:46:57 +0800

于 2010年11月25日 01:20, Junio C Hamano 写道:
> Jiang Xin <[email-masked]> writes:
> 
>> When patch file generated against two non-git directories using
>> 'git diff --binary --no-index' without '--no-prefix', the patch
>> file has patch level greater then 1, and should be applied with
>> '-p2' option. But it does not work if there are binary differ
>> in the patch file, it is because in one case the patch level is
>> not properly handled.
>>
>> Signed-off-by: Jiang Xin <[email-masked]>
> 
> Can you please add a testcase to protect your fix from getting broken by
> later changes by other people, perhaps to t/t4120?
> 

Yes, I add a testcase in t/t4120, and I will send it as a new PATCH.
The new testcase is like following:

+test_expect_success 'apply git diff with -p2 and use default name from header' '
+       sed -e "/^\(---\|+++\) / d" patch.file > patch.newheader &&
+       cp file1.saved file1 &&
+       git apply -p2 patch.newheader
+'
+

> By the way, this codepath is shared by all forms of patches "diff --git"
> header, not just binary.  Do you see a similar breakage with --no-prefix
> patches that are not binary, and if not why?
> 

The breakage will appear under these circumstances:
* the patch is in git style: header with "diff --git".
* the header does not contain '--- path/to/old' and '+++ path/to/new'.
* has a patch level greater than 1.

When I do `git diff` against binary files, I find the patch header does not has
'--- path/to/old' and '+++ path/to/new'. May be there exist other cases, but
I'm not sure.

>> ---
>>  builtin/apply.c |    3 ++-
>>  1 files changed, 2 insertions(+), 1 deletions(-)
>>
>> diff --git a/builtin/apply.c b/builtin/apply.c
>> index 23c18c5..d603e37 100644
>> --- a/builtin/apply.c
>> +++ b/builtin/apply.c
>> @@ -1126,6 +1126,7 @@ static char *git_header_name(char *line, int llen)
>>  	 * form.
>>  	 */
>>  	for (len = 0 ; ; len++) {
>> +		int nslash = p_value;
>>  		switch (name[len]) {
>>  		default:
>>  			continue;
>> @@ -1137,7 +1138,7 @@ static char *git_header_name(char *line, int llen)
>>  				char c = *second++;
>>  				if (c == '\n')
>>  					return NULL;
>> -				if (c == '/')
>> +				if (c == '/' && --nslash <= 0)
>>  					break;
>>  			}
>>  			if (second[len] == '\n' && !memcmp(name, second, len)) {
>> -- 
>> 1.7.3.2.245.g03276.dirty

-- 
Jiang Xin