Ref-count the filespecs used by diffcore

Rather than copy the filespecs when introducing new versions of them
(for rename or copy detection), use a refcount and increment the count
when reusing the diff_filespec.

This avoids unnecessary allocations, but the real reason behind this is
a future enhancement: we will want to track shared data across the
copy/rename detection.  In order to efficiently notice when a filespec
is used by a rename, the rename machinery wants to keep track of a
rename usage count which is shared across all different users of the
filespec.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/diffcore.h b/diffcore.h
index eb618b1..30055ac 100644
--- a/diffcore.h
+++ b/diffcore.h
@@ -29,6 +29,7 @@ struct diff_filespec {
 	void *cnt_data;
 	const char *funcname_pattern_ident;
 	unsigned long size;
+	int count;               /* Reference count */
 	int xfrm_flags;		 /* for use by the xfrm */
 	unsigned short mode;	 /* file mode */
 	unsigned sha1_valid : 1; /* if true, use sha1 and trust mode;
@@ -43,6 +44,7 @@ struct diff_filespec {
 };
 
 extern struct diff_filespec *alloc_filespec(const char *);
+extern void free_filespec(struct diff_filespec *);
 extern void fill_filespec(struct diff_filespec *, const unsigned char *,
 			  unsigned short);