Merge branch 'nd/traces'

* nd/traces:
  git.txt: document GIT_TRACE_PACKET
  core: use env variable instead of config var to turn on logging pack access

cache.h

@@ -774,9 +774,6 @@ extern int parse_sha1_header(const char *hdr, unsigned long *sizep);
 /* global flag to enable extra checks when accessing packed objects */
 extern int do_check_packed_object_crc;
 
-/* for development: log offset of pack access */
-extern const char *log_pack_access;
-
 extern int check_sha1_signature(const unsigned char *sha1, void *buf, unsigned long size, const char *type);
 
 extern int move_temp_to_file(const char *tmpfile, const char *filename);