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, 30 insertions, 4 deletions

diff --git a/revision.c b/revision.c
index 8a29cb03c5..c141a398ac 100644
--- a/revision.c
+++ b/revision.c
@@ -1289,12 +1289,14 @@ void add_index_objects_to_pending(struct rev_info *revs, unsigned flags)
 	}
 }
 
-static int add_parents_only(struct rev_info *revs, const char *arg_, int flags)
+static int add_parents_only(struct rev_info *revs, const char *arg_, int flags,
+			    int exclude_parent)
 {
 	unsigned char sha1[20];
 	struct object *it;
 	struct commit *commit;
 	struct commit_list *parents;
+	int parent_number;
 	const char *arg = arg_;
 
 	if (*arg == '^') {
@@ -1316,7 +1318,15 @@ static int add_parents_only(struct rev_info *revs, const char *arg_, int flags)
 	if (it->type != OBJ_COMMIT)
 		return 0;
 	commit = (struct commit *)it;
-	for (parents = commit->parents; parents; parents = parents->next) {
+	if (exclude_parent &&
+	    exclude_parent > commit_list_count(commit->parents))
+		return 0;
+	for (parents = commit->parents, parent_number = 1;
+	     parents;
+	     parents = parents->next, parent_number++) {
+		if (exclude_parent && parent_number != exclude_parent)
+			continue;
+
 		it = &parents->item->object;
 		it->flags |= flags;
 		add_rev_cmdline(revs, it, arg_, REV_CMD_PARENTS_ONLY, flags);
@@ -1519,17 +1529,33 @@ int handle_revision_arg(const char *arg_, struct rev_info *revs, int flags, unsi
 		}
 		*dotdot = '.';
 	}
+
 	dotdot = strstr(arg, "^@");
 	if (dotdot && !dotdot[2]) {
 		*dotdot = 0;
-		if (add_parents_only(revs, arg, flags))
+		if (add_parents_only(revs, arg, flags, 0))
 			return 0;
 		*dotdot = '^';
 	}
 	dotdot = strstr(arg, "^!");
 	if (dotdot && !dotdot[2]) {
 		*dotdot = 0;
-		if (!add_parents_only(revs, arg, flags ^ (UNINTERESTING | BOTTOM)))
+		if (!add_parents_only(revs, arg, flags ^ (UNINTERESTING | BOTTOM), 0))
+			*dotdot = '^';
+	}
+	dotdot = strstr(arg, "^-");
+	if (dotdot) {
+		int exclude_parent = 1;
+
+		if (dotdot[2]) {
+			char *end;
+			exclude_parent = strtoul(dotdot + 2, &end, 10);
+			if (*end != '\0' || !exclude_parent)
+				return -1;
+		}
+
+		*dotdot = 0;
+		if (!add_parents_only(revs, arg, flags ^ (UNINTERESTING | BOTTOM), exclude_parent))
 			*dotdot = '^';
 	}