Extended SHA1 -- "rev^@" syntax to mean "all parents"

A short-hand "rev^@" is understood to be "all parents of the
named commit" with this patch.  So you can do

	git show v1.0.0^@

to view the parents of a merge commit,

	gitk ^v1.0.0^@ v1.0.4

to view the log between two revs (including the bottom one), and

	git diff --cc v1.1.0 v1.0.0^@

to inspect what got changed from the merge parents of v1.0.0 to v1.1.0.

This might be just my shiny new toy that is not very useful in
practice.  I needed it to do the multi-tree diff on Len's
infamous 12-way Octopus; typing "diff --cc funmerge funmerge^1
funmerge^2 funmerge^3 ..." was too painful.

[jc: taking suggestions from Linus and Johannes to match expectations
from shell users who are used to see $@ or $* either of which makes
sense.  I tend to write "$@" more often so...]

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

diff --git a/revision.c b/revision.c
index f2a9f25..d1f85a8 100644 (file)
--- a/revision.c
+++ b/revision.c
@@ -477,6 +477,36 @@ static void handle_all(struct rev_info *revs, unsigned flags)
        for_each_ref(handle_one_ref);
 }
 
+static int add_parents_only(struct rev_info *revs, const char *arg, int flags)
+{
+       unsigned char sha1[20];
+       struct object *it;
+       struct commit *commit;
+       struct commit_list *parents;
+
+       if (*arg == '^') {
+               flags ^= UNINTERESTING;
+               arg++;
+       }
+       if (get_sha1(arg, sha1))
+               return 0;
+       while (1) {
+               it = get_reference(revs, arg, sha1, 0);
+               if (strcmp(it->type, tag_type))
+                       break;
+               memcpy(sha1, ((struct tag*)it)->tagged->sha1, 20);
+       }
+       if (strcmp(it->type, commit_type))
+               return 0;
+       commit = (struct commit *)it;
+       for (parents = commit->parents; parents; parents = parents->next) {
+               it = &parents->item->object;
+               it->flags |= flags;
+               add_pending_object(revs, it, arg);
+       }
+       return 1;
+}
+
 void init_revisions(struct rev_info *revs)
 {
        memset(revs, 0, sizeof(*revs));
@@ -746,6 +776,13 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, const ch
                        }
                        *dotdot = '.';
                }
+               dotdot = strstr(arg, "^@");
+               if (dotdot && !dotdot[2]) {
+                       *dotdot = 0;
+                       if (add_parents_only(revs, arg, flags))
+                               continue;
+                       *dotdot = '^';
+               }
                local_flags = 0;
                if (*arg == '^') {
                        local_flags = UNINTERESTING;