apply: use the right attribute for paths in non-Git patches

We parse each patchfile and find to what path it applies to and then
use that name to consult the attribute system to find what
whitespace rules to be applied, and also which target file (either
in the working tree or in the index) to replay the changes the patch
represents.

A non-Git patch is taken as relative to the current working
directory, and the prefix_patches() helper function introduced in
56185f49 (git-apply: require -p<n> when working in a subdirectory.,
2007-02-19) is used to prepend the prefix to these names found in
the patch input.

However, this prepending of the prefix to the pathnames is done
after the patch is fully parsed and affects only what target files
are patched.  Because the attributes are checked against the names
found in the patch during the parsing, not against the final path,
whitespace checks that are done during parsing end up using
attributes for a wrong path.

Because a Git-generated patch records the full path to the target
with -p$n prefix (e.g. a/ and b/) and we apply it relative to the
top of the working tree, prefix_patches() is a no-op and this
problem does not manifest for them.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
apply: hoist use_patch() helper for path exclusion up

We will be adding a caller to the function a bit earlier in this
file in a later patch.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
apply: omit ws check for excluded paths

Whitespace breakages are checked while the patch is being parsed.
Disable them at the beginning of parse_chunk(), where each
individual patch is parsed, immediately after we learn what path the
patch applies to and before we start parsing the changes.

One may naively think we should be able to not just skip the
whitespace checks but simply fast-forward to the next patch without
doing anything once use_patch() tells us that this patch is not
going to be used.  But in reality we cannot really skip much of the
parsing, primarily because parsing "@@ -k,l +m,n @@" lines and
counting the input lines is how we determine the boundaries of
individual patches.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
Merge branch 'jc/apply-ws-prefix' into jch

* jc/apply-ws-prefix:
  apply: omit ws check for excluded paths
  apply: hoist use_patch() helper for path exclusion up
  apply: use the right attribute for paths in non-Git patches

Conflicts:
	builtin/apply.c