Merge branch 'js/merge-base'

diff --combined revision.c
index ab89c22417cace2ee56cd88a7135967690be586a,b4157cbb6de7dba184ff1ca9a558769338154a0b..a7750e626b63815cb0a579287220b289af7311b3
--- 1/revision.c
--- 2/revision.c
+++ b/revision.c
@@@ -537,6 -537,18 +537,18 @@@ void init_revisions(struct rev_info *re
        diff_setup(&revs->diffopt);
  }
  
+ static void add_pending_commit_list(struct rev_info *revs,
+                                     struct commit_list *commit_list,
+                                     unsigned int flags)
+ {
+       while (commit_list) {
+               struct object *object = &commit_list->item->object;
+               object->flags |= flags;
+               add_pending_object(revs, object, sha1_to_hex(object->sha1));
+               commit_list = commit_list->next;
+       }
+ }
+ 
  /*
   * Parse revision information, filling in the "rev_info" structure,
   * and removing the used arguments from the argument list.
@@@ -772,27 -784,46 +784,46 @@@ int setup_revisions(int argc, const cha
                        unsigned char from_sha1[20];
                        const char *next = dotdot + 2;
                        const char *this = arg;
+                       int symmetric = *next == '.';
+                       unsigned int flags_exclude = flags ^ UNINTERESTING;
+ 
                        *dotdot = 0;
+                       next += symmetric;
+ 
                        if (!*next)
                                next = "HEAD";
                        if (dotdot == arg)
                                this = "HEAD";
                        if (!get_sha1(this, from_sha1) &&
                            !get_sha1(next, sha1)) {
-                               struct object *exclude;
-                               struct object *include;
- 
-                               exclude = get_reference(revs, this, from_sha1, flags ^ UNINTERESTING);
-                               include = get_reference(revs, next, sha1, flags);
-                               if (!exclude || !include)
-                                       die("Invalid revision range %s..%s", arg, next);
+                               struct commit *a, *b;
+                               struct commit_list *exclude;
+ 
+                               a = lookup_commit_reference(from_sha1);
+                               b = lookup_commit_reference(sha1);
+                               if (!a || !b) {
+                                       die(symmetric ?
+                                           "Invalid symmetric difference expression %s...%s" :
+                                           "Invalid revision range %s..%s",
+                                           arg, next);
+                               }
  
                                if (!seen_dashdash) {
                                        *dotdot = '.';
                                        verify_non_filename(revs->prefix, arg);
                                }
-                               add_pending_object(revs, exclude, this);
-                               add_pending_object(revs, include, next);
+ 
+                               if (symmetric) {
+                                       exclude = get_merge_bases(a, b, 1);
+                                       add_pending_commit_list(revs, exclude,
+                                                               flags_exclude);
+                                       free_commit_list(exclude);
+                                       a->object.flags |= flags;
+                               } else
+                                       a->object.flags |= flags_exclude;
+                               b->object.flags |= flags;
+                               add_pending_object(revs, &a->object, this);
+                               add_pending_object(revs, &b->object, next);
                                continue;
                        }
                        *dotdot = '.';
@@@ -852,7 -883,8 +883,7 @@@
        }
        if (revs->combine_merges) {
                revs->ignore_merges = 0;
 -              if (revs->dense_combined_merges &&
 -                  (revs->diffopt.output_format != DIFF_FORMAT_DIFFSTAT))
 +              if (revs->dense_combined_merges && !revs->diffopt.output_format)
                        revs->diffopt.output_format = DIFF_FORMAT_PATCH;
        }
        revs->diffopt.abbrev = revs->abbrev;