revision: new rev^-n shorthand for rev^n..rev

"git log rev^..rev" is commonly used to show all work done on and merged
from a side branch. This patch introduces a shorthand "rev^-" for this
and additionally allows "rev^-$n" to mean "reachable from rev, excluding
what is reachable from the nth parent of rev". For example, for a
two-parent merge, you can use rev^-2 to get the set of commits which were
made to the main branch while the topic branch was prepared.

Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 41 insertions, 13 deletions

diff --git a/builtin/rev-parse.c b/builtin/rev-parse.c
index 76cf05e..4da1f1d 100644
--- a/builtin/rev-parse.c
+++ b/builtin/rev-parse.c
@@ -298,14 +298,30 @@ static int try_parent_shorthands(const char *arg)
 	unsigned char sha1[20];
 	struct commit *commit;
 	struct commit_list *parents;
-	int parents_only;
-
-	if ((dotdot = strstr(arg, "^!")))
-		parents_only = 0;
-	else if ((dotdot = strstr(arg, "^@")))
-		parents_only = 1;
-
-	if (!dotdot || dotdot[2])
+	int parent_number;
+	int include_rev = 0;
+	int include_parents = 0;
+	int exclude_parent = 0;
+
+	if ((dotdot = strstr(arg, "^!"))) {
+		include_rev = 1;
+		if (dotdot[2])
+			return 0;
+	} else if ((dotdot = strstr(arg, "^@"))) {
+		include_parents = 1;
+		if (dotdot[2])
+			return 0;
+	} else if ((dotdot = strstr(arg, "^-"))) {
+		include_rev = 1;
+		exclude_parent = 1;
+
+		if (dotdot[2]) {
+			char *end;
+			exclude_parent = strtoul(dotdot + 2, &end, 10);
+			if (*end != '\0' || !exclude_parent)
+				return 0;
+		}
+	} else
 		return 0;
 
 	*dotdot = 0;
@@ -314,12 +330,24 @@ static int try_parent_shorthands(const char *arg)
 		return 0;
 	}
 
-	if (!parents_only)
-		show_rev(NORMAL, sha1, arg);
 	commit = lookup_commit_reference(sha1);
-	for (parents = commit->parents; parents; parents = parents->next)
-		show_rev(parents_only ? NORMAL : REVERSED,
-				parents->item->object.oid.hash, arg);
+	if (exclude_parent &&
+	    exclude_parent > commit_list_count(commit->parents)) {
+		*dotdot = '^';
+		return 0;
+	}
+
+	if (include_rev)
+		show_rev(NORMAL, sha1, arg);
+	for (parents = commit->parents, parent_number = 1;
+	     parents;
+	     parents = parents->next, parent_number++) {
+		if (exclude_parent && parent_number != exclude_parent)
+			continue;
+
+		show_rev(include_parents ? NORMAL : REVERSED,
+			 parents->item->object.oid.hash, arg);
+	}
 
 	*dotdot = '^';
 	return 1;