Merge branch 'nd/log-show-linear-break'

Attempts to show where a single-strand-of-pearls break in "git log"
output.

* nd/log-show-linear-break:
  log: add --show-linear-break to help see non-linear history
  object.h: centralize object flag allocation

sha1_name.c

@@ -819,6 +819,8 @@ static int get_sha1_1(const char *name, int len, unsigned char *sha1, unsigned l
  * For future extension, ':/!' is reserved. If you want to match a message
  * beginning with a '!', you have to repeat the exclamation mark.
  */
+
+/* Remember to update object flag allocation in object.h */
 #define ONELINE_SEEN (1u<<20)
 
 static int handle_one_ref(const char *path,