Merge branch 'vn/revision-shorthand-for-side-branch-log'

"git log rev^..rev" is an often-used revision range specification
to show what was done on a side branch merged at rev.  This has
gained a short-hand "rev^-1".  In general "rev^-$n" is the same as
"^rev^$n rev", i.e. what has happened on other branches while the
history leading to nth parent was looking the other way.

* vn/revision-shorthand-for-side-branch-log:
revision: new rev^-n shorthand for rev^n..rev

diff --combined revision.c
index 969b3d149f2327a00b159e17fa7f63005aa90dff,c141a398acd0a5e43e049f37d3f49b6ced70a14a..b37dbec378f3ae1a33d00d591c1042c609e45fa4
--- 1/revision.c
--- 2/revision.c
+++ b/revision.c
@@@ -1275,7 -1275,7 +1275,7 @@@ void add_index_objects_to_pending(struc
                if (S_ISGITLINK(ce->ce_mode))
                        continue;
  
 -              blob = lookup_blob(ce->sha1);
 +              blob = lookup_blob(ce->oid.hash);
                if (!blob)
                        die("unable to add index blob to traversal");
                add_pending_object_with_path(revs, &blob->object, "",
@@@ -1289,12 -1289,14 +1289,14 @@@
        }
  }
  
- 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 +1318,15 @@@
        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 +1529,33 @@@ int handle_revision_arg(const char *arg
                }
                *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 = '^';
        }