grep: stop looking at random places for .gitattributes

grep searches for .gitattributes using "name" field in struct
grep_source but that field is not real on-disk path name. For example,
"grep pattern rev" fills the field with "rev:path", and Git looks for
.gitattributes in the (non-existent but exploitable) path "rev:path"
instead of "path".

This patch passes real paths down to grep_source_load_driver() when:

 - grep on work tree
 - grep on the index
 - grep a commit (or a tag if it points to a commit)

so that these cases look up .gitattributes at proper paths.
.gitattributes lookup is disabled in all other cases.

Initial-work-by: Jeff King <peff@peff.net>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/grep.h b/grep.h
index d66b19712c..1f32944be1 100644
--- a/grep.h
+++ b/grep.h
@@ -144,11 +144,13 @@ struct grep_source {
 	char *buf;
 	unsigned long size;
 
+	char *path; /* for attribute lookups */
 	struct userdiff_driver *driver;
 };
 
 void grep_source_init(struct grep_source *gs, enum grep_source_type type,
-		      const char *name, const void *identifier);
+		      const char *name, const char *path,
+		      const void *identifier);
 void grep_source_clear_data(struct grep_source *gs);
 void grep_source_clear(struct grep_source *gs);
 void grep_source_load_driver(struct grep_source *gs);