Documentation: document pitfalls with 3-way merge

diff --git a/revision.c b/revision.c
index ac20d1aaed7b5e1a52682dfd196f87e2f94e87c7..f82b833fbceada4c4b32e669fd33966c751249e8 100644 (file)
--- a/revision.c
+++ b/revision.c
@@ -1420,26 +1420,40 @@ int handle_revision_arg(const char *arg_, struct rev_info *revs, int flags, unsi
                }
                if (!get_sha1_committish(this, from_sha1) &&
                    !get_sha1_committish(next, sha1)) {
-                       struct commit *a, *b;
-                       struct commit_list *exclude;
-
-                       a = lookup_commit_reference(from_sha1);
-                       b = lookup_commit_reference(sha1);
-                       if (!a || !b) {
-                               if (revs->ignore_missing)
-                                       return 0;
-                               die(symmetric ?
-                                   "Invalid symmetric difference expression %s...%s" :
-                                   "Invalid revision range %s..%s",
-                                   arg, next);
-                       }
+                       struct object *a_obj, *b_obj;
 
                        if (!cant_be_filename) {
                                *dotdot = '.';
                                verify_non_filename(revs->prefix, arg);
                        }
 
-                       if (symmetric) {
+                       a_obj = parse_object(from_sha1);
+                       b_obj = parse_object(sha1);
+                       if (!a_obj || !b_obj) {
+                       missing:
+                               if (revs->ignore_missing)
+                                       return 0;
+                               die(symmetric
+                                   ? "Invalid symmetric difference expression %s"
+                                   : "Invalid revision range %s", arg);
+                       }
+
+                       if (!symmetric) {
+                               /* just A..B */
+                               a_flags = flags_exclude;
+                       } else {
+                               /* A...B -- find merge bases between the two */
+                               struct commit *a, *b;
+                               struct commit_list *exclude;
+
+                               a = (a_obj->type == OBJ_COMMIT
+                                    ? (struct commit *)a_obj
+                                    : lookup_commit_reference(a_obj->sha1));
+                               b = (b_obj->type == OBJ_COMMIT
+                                    ? (struct commit *)b_obj
+                                    : lookup_commit_reference(b_obj->sha1));
+                               if (!a || !b)
+                                       goto missing;
                                exclude = get_merge_bases(a, b, 1);
                                add_rev_cmdline_list(revs, exclude,
                                                     REV_CMD_MERGE_BASE,
@@ -1447,17 +1461,18 @@ int handle_revision_arg(const char *arg_, struct rev_info *revs, int flags, unsi
                                add_pending_commit_list(revs, exclude,
                                                        flags_exclude);
                                free_commit_list(exclude);
+
                                a_flags = flags | SYMMETRIC_LEFT;
-                       } else
-                               a_flags = flags_exclude;
-                       a->object.flags |= a_flags;
-                       b->object.flags |= flags;
-                       add_rev_cmdline(revs, &a->object, this,
+                       }
+
+                       a_obj->flags |= a_flags;
+                       b_obj->flags |= flags;
+                       add_rev_cmdline(revs, a_obj, this,
                                        REV_CMD_LEFT, a_flags);
-                       add_rev_cmdline(revs, &b->object, next,
+                       add_rev_cmdline(revs, b_obj, next,
                                        REV_CMD_RIGHT, flags);
-                       add_pending_object(revs, &a->object, this);
-                       add_pending_object(revs, &b->object, next);
+                       add_pending_object(revs, a_obj, this);
+                       add_pending_object(revs, b_obj, next);
                        return 0;
                }
                *dotdot = '.';