status: add --[no-]ahead-behind to status and commit for V2 format.

Teach "git status" and "git commit" to accept "--no-ahead-behind"
and "--ahead-behind" arguments to request quick or full ahead/behind
reporting.

When "--no-ahead-behind" is given, the existing porcelain V2 line
"branch.ab +x -y" is replaced with a new "branch.ab +? -?" line.
This indicates that the branch and its upstream are or are not equal
without the expense of computing the full ahead/behind values.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 21 insertions, 9 deletions

diff --git a/wt-status.c b/wt-status.c
index 1137f27..7a560c1 100644
--- a/wt-status.c
+++ b/wt-status.c
@@ -136,6 +136,7 @@ void wt_status_prepare(struct wt_status *s)
 	s->ignored.strdup_strings = 1;
 	s->show_branch = -1;  /* unspecified */
 	s->show_stash = 0;
+	s->ahead_behind_flags = AHEAD_BEHIND_UNSPECIFIED;
 	s->display_comment_prefix = 0;
 }
 
@@ -1883,18 +1884,19 @@ static void wt_porcelain_print(struct wt_status *s)
  *
  *    <upstream> ::= the upstream branch name, when set.
  *
- *       <ahead> ::= integer ahead value, when upstream set
- *                   and the commit is present (not gone).
- *
- *      <behind> ::= integer behind value, when upstream set
- *                   and commit is present.
+ *       <ahead> ::= integer ahead value or '?'.
  *
+ *      <behind> ::= integer behind value or '?'.
  *
  * The end-of-line is defined by the -z flag.
  *
  *                 <eol> ::= NUL when -z,
  *                           LF when NOT -z.
  *
+ * When an upstream is set and present, the 'branch.ab' line will
+ * be printed with the ahead/behind counts for the branch and the
+ * upstream.  When AHEAD_BEHIND_QUICK is requested and the branches
+ * are different, '?' will be substituted for the actual count.
  */
 static void wt_porcelain_v2_print_tracking(struct wt_status *s)
 {
@@ -1934,15 +1936,25 @@ static void wt_porcelain_v2_print_tracking(struct wt_status *s)
 		/* Lookup stats on the upstream tracking branch, if set. */
 		branch = branch_get(branch_name);
 		base = NULL;
-		ab_info = (stat_tracking_info(branch, &nr_ahead, &nr_behind,
-					      &base, AHEAD_BEHIND_FULL) >= 0);
+		ab_info = stat_tracking_info(branch, &nr_ahead, &nr_behind,
+					     &base, s->ahead_behind_flags);
 		if (base) {
 			base = shorten_unambiguous_ref(base, 0);
 			fprintf(s->fp, "# branch.upstream %s%c", base, eol);
 			free((char *)base);
 
-			if (ab_info)
-				fprintf(s->fp, "# branch.ab +%d -%d%c", nr_ahead, nr_behind, eol);
+			if (ab_info > 0) {
+				/* different */
+				if (nr_ahead || nr_behind)
+					fprintf(s->fp, "# branch.ab +%d -%d%c",
+						nr_ahead, nr_behind, eol);
+				else
+					fprintf(s->fp, "# branch.ab +? -?%c",
+						eol);
+			} else if (!ab_info) {
+				/* same */
+				fprintf(s->fp, "# branch.ab +0 -0%c", eol);
+			}
 		}
 	}