[PATCH] fix segfault in fsck-cache

Here is how to trigger it:

   echo blob 100 > .git/objects/00/ae4e8d3208e09f2cf7a38202a126f728cadb49

Then run fsck-cache. It will try to unpack after the header to calculate 
the hash, inflate returns total_out == 0 and memcpy() dies.

The patch below seems to work with ZLIB 1.1 and 1.2.

Signed-off-by: Andreas Gal <gal@uci.edu>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

sha1_file.c

@@ -155,6 +155,8 @@ void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned l
 
 	inflateInit(&stream);
 	ret = inflate(&stream, 0);
+       if (ret < Z_OK)
+               return NULL;
 	if (sscanf(buffer, "%10s %lu", type, size) != 2)
 		return NULL;