Re: [PATCH v4 2/2] apply: reload .gitattributes after patching it

["brian m. carlson" <sandals@crustytoothpaste.net>]

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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.

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.
-- 
brian m. carlson: Houston, Texas, US
OpenPGP: https://keybase.io/bk2204

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