rev-list --left-right

The output from "symmetric diff", i.e. A...B, does not
distinguish between commits that are reachable from A and the
ones that are reachable from B.  In this picture, such a
symmetric diff includes commits marked with a and b.

         x---b---b  branch B
        / \ /
       /   .
      /   / \
     o---x---a---a  branch A

However, you cannot tell which ones are 'a' and which ones are
'b' from the output.  Sometimes this is frustrating.  This adds
an output option, --left-right, to rev-list.

        rev-list --left-right A...B

would show ones reachable from A prefixed with '<' and the ones
reachable from B prefixed with '>'.

When combined with --boundary, boundary commits (the ones marked
with 'x' in the above picture) are shown with prefix '-', so you
would see list that looks like this:

    git rev-list --left-right --boundary --pretty=oneline A...B

    >bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb 3rd on b
    >bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb 2nd on b
    <aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa 3rd on a
    <aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa 2nd on a
    -xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 1st on b
    -xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 1st on a

Signed-off-by: Junio C Hamano <junkio@cox.net>

1 files changed, 11 insertions, 0 deletions

diff --git a/builtin-rev-list.c b/builtin-rev-list.c
index fb7fc9214..4364035e1 100644
--- a/builtin-rev-list.c
+++ b/builtin-rev-list.c
@@ -45,6 +45,7 @@ static int bisect_list;
 static int show_timestamp;
 static int hdr_termination;
 static const char *header_prefix;
+static int show_left_right;
 
 static void show_commit(struct commit *commit)
 {
@@ -54,6 +55,12 @@ static void show_commit(struct commit *commit)
 		fputs(header_prefix, stdout);
 	if (commit->object.flags & BOUNDARY)
 		putchar('-');
+	else if (show_left_right) {
+		if (commit->object.flags & SYMMETRIC_LEFT)
+			putchar('<');
+		else
+			putchar('>');
+	}
 	if (revs.abbrev_commit && revs.abbrev)
 		fputs(find_unique_abbrev(commit->object.sha1, revs.abbrev),
 		      stdout);
@@ -240,6 +247,10 @@ int cmd_rev_list(int argc, const char **argv, const char *prefix)
 			bisect_list = 1;
 			continue;
 		}
+		if (!strcmp(arg, "--left-right")) {
+			show_left_right = 1;
+			continue;
+		}
 		if (!strcmp(arg, "--stdin")) {
 			if (read_from_stdin++)
 				die("--stdin given twice?");