Fix merge-base from getting confused.

On Sat, 30 Jul 2005, Linus Torvalds wrote:
>
> Yup, it's git-merge-base, and it is confused by the same thing that
> confused git-rev-list.

Hmm.. Here's a tentative fix. I'm not really happy with it, and maybe
somebody else can come up with a better one. I think this one ends up
being quite a bit more expensive than the old one (it will look up _all_
common parents that have a child that isn't common, and then select the
newest one of the bunch), but I haven't really thought it through very
much.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/merge-base.c b/merge-base.c
index 12ebb95..5919566 100644 (file)
--- a/merge-base.c
+++ b/merge-base.c
@@ -2,54 +2,50 @@
 #include "cache.h"
 #include "commit.h"
 
-static struct commit *process_list(struct commit_list **list_p, int this_mark,
-                                  int other_mark)
-{
-       struct commit *item = (*list_p)->item;
-
-       if (item->object.flags & other_mark) {
-               return item;
-       } else {
-               pop_most_recent_commit(list_p, this_mark);
-       }
-       return NULL;
-}
-
 static struct commit *common_ancestor(struct commit *rev1, struct commit *rev2)
 {
-       struct commit_list *rev1list = NULL;
-       struct commit_list *rev2list = NULL;
+       struct commit_list *list = NULL;
+       struct commit_list *result = NULL;
 
-       commit_list_insert(rev1, &rev1list);
-       rev1->object.flags |= 0x1;
-       commit_list_insert(rev2, &rev2list);
-       rev2->object.flags |= 0x2;
+       if (rev1 == rev2)
+               return rev1;
 
        parse_commit(rev1);
        parse_commit(rev2);
 
-       while (rev1list || rev2list) {
-               struct commit *ret;
-               if (!rev1list) {
-                       // process 2
-                       ret = process_list(&rev2list, 0x2, 0x1);
-               } else if (!rev2list) {
-                       // process 1
-                       ret = process_list(&rev1list, 0x1, 0x2);
-               } else if (rev1list->item->date < rev2list->item->date) {
-                       // process 2
-                       ret = process_list(&rev2list, 0x2, 0x1);
-               } else {
-                       // process 1
-                       ret = process_list(&rev1list, 0x1, 0x2);
+       rev1->object.flags |= 1;
+       rev2->object.flags |= 2;
+       insert_by_date(rev1, &list);
+       insert_by_date(rev2, &list);
+
+       while (list) {
+               struct commit *commit = list->item;
+               struct commit_list *tmp = list, *parents;
+               int flags = commit->object.flags & 3;
+
+               list = list->next;
+               free(tmp);
+               switch (flags) {
+               case 3:
+                       insert_by_date(commit, &result);
+                       continue;
+               case 0:
+                       die("git-merge-base: commit without either parent?");
                }
-               if (ret) {
-                       free_commit_list(rev1list);
-                       free_commit_list(rev2list);
-                       return ret;
+               parents = commit->parents;
+               while (parents) {
+                       struct commit *p = parents->item;
+                       parents = parents->next;
+                       if ((p->object.flags & flags) == flags)
+                               continue;
+                       parse_commit(p);
+                       p->object.flags |= flags;
+                       insert_by_date(p, &list);
                }
        }
-       return NULL;
+       if (!result)
+               return NULL;
+       return result->item;
 }
 
 int main(int argc, char **argv)
@@ -64,6 +60,8 @@ int main(int argc, char **argv)
        }
        rev1 = lookup_commit_reference(rev1key);
        rev2 = lookup_commit_reference(rev2key);
+       if (!rev1 || !rev2)
+               return 1;
        ret = common_ancestor(rev1, rev2);
        if (!ret)
                return 1;