From: Phillip Wood <phillip.wood123@gmail.com>
Date: Tue, 20 Aug 2019 08:52:48 GMT
Subject: Re: [PATCH v4 2/2] apply: reload .gitattributes after patching it
Message-ID: <18fcc7db-7c09-3fbf-1e3f-81be99f4bb17@gmail.com>
In-Reply-To: <20190820024505.GH365197@genre.crustytoothpaste.net>

Hi Brian

On 20/08/2019 03:45, brian m. carlson wrote:
> On 2019-08-19 at 09:41:42, Phillip Wood wrote:
>> Hi Brian
>>
>> On 18/08/2019 19:44, brian m. carlson wrote:
>>> When applying multiple patches with git am, or when rebasing using the
>>> am backend, it's possible that one of our patches has updated a
>>> gitattributes file. Currently, we cache this information, so if a
>>> file in a subsequent patch has attributes applied, the file will be
>>> written out with the attributes in place as of the time we started the
>>> rebase or am operation, not with the attributes applied by the previous
>>> patch. This problem does not occur when using the -m or -i flags to
>>> rebase.
>>
>> Do you know why -m and -i aren't affected?
> 
> I had to look, but I believe the answer is because they use the
> sequencer, and the sequencer calls git merge-recursive as a separate
> process, and so the writing of the tree is only done in a subprocess,
> which can't persist state.

The sequencer has been running in a single process for a while now. We 
do fork for 'git merge' sometimes when processing 'merge' commands but 
'pick' commands are all done in a single process by calling 
do_recursive_merge().

Best Wishes

Phillip

> Should we move the merge-recursive code into the main process, we'll
> likely have the same problem there.
> 
>>> diff --git a/apply.c b/apply.c
>>> index cde95369bb..d57bc635e4 100644
>>> --- a/apply.c
>>> +++ b/apply.c
>>> @@ -4643,6 +4643,7 @@ static int apply_patch(struct apply_state *state,
>>>    	struct patch *list = NULL, **listp = &list;
>>>    	int skipped_patch = 0;
>>>    	int res = 0;
>>> +	int flush_attributes = 0;
>>>    	state->patch_input_file = filename;
>>>    	if (read_patch_file(&buf, fd) < 0)
>>> @@ -4670,6 +4671,10 @@ static int apply_patch(struct apply_state *state,
>>>    			patch_stats(state, patch);
>>>    			*listp = patch;
>>>    			listp = &patch->next;
>>> +
>>> +			if ((patch->new_name && ends_with_path_components(patch->new_name, GITATTRIBUTES_FILE)) ||
>>> +			    (patch->old_name && ends_with_path_components(patch->old_name, GITATTRIBUTES_FILE)))
>>> +				flush_attributes = 1;
>>
>> style nit - these lines are very long compared to 80 characters
> 
> They are.  They aren't two different from other lines in the file, and I
> thought that leaving them that way would preserve the similarities, but
> I can also wrap them.  I'll send out a v5 with wrapped lines.
> 
>>> diff --git a/convert.c b/convert.c
>>> index 94ff837649..030e9b81b9 100644
>>> --- a/convert.c
>>> +++ b/convert.c
>>> @@ -1293,10 +1293,11 @@ struct conv_attrs {
>>>    	const char *working_tree_encoding; /* Supported encoding or default encoding if NULL */
>>>    };
>>> +static struct attr_check *check;
>>
>> I was concerned about the impact adding a file global if we ever want to
>> multi-thread this for submodules, but looking through the file there are a
>> couple of others already so this isn't creating a new problem.
>>> +
>>>    static void convert_attrs(const struct index_state *istate,
>>>    			  struct conv_attrs *ca, const char *path)
>>>    {
>>> -	static struct attr_check *check;
>>>    	struct attr_check_item *ccheck = NULL;
>>>    	if (!check) {
>>> @@ -1339,6 +1340,12 @@ static void convert_attrs(const struct index_state *istate,
>>>    		ca->crlf_action = CRLF_AUTO_INPUT;
>>>    }
> 
> The portion I've included above demonstrates that this was already a
> static variable, just one hidden in a function.  So yeah, this is no
> worse than it already was.
>