builtin-grep: documentation
[gitweb.git] / merge-base.c
index 923256c821582f38daffed4fb0df2a97fe66d74b..07f5ab4d1c72afeac5e3f193cefe91801ee9a9c9 100644 (file)
@@ -80,15 +80,100 @@ static struct commit *interesting(struct commit_list *list)
  * Now, list does not have any interesting commit.  So we find the newest
  * commit from the result list that is not marked uninteresting.  Which is
  * commit B.
+ *
+ *
+ * Another pathological example how this thing can fail to mark an ancestor
+ * of a merge base as UNINTERESTING without the postprocessing phase.
+ *
+ *               2
+ *               H
+ *         1    / \
+ *         G   A   \
+ *         |\ /     \ 
+ *         | B       \
+ *         |  \       \
+ *          \  C       F
+ *           \  \     / 
+ *            \  D   /   
+ *             \ |  /
+ *              \| /
+ *               E
+ *
+ *      list                   A B C D E F G H
+ *      G1 H2                  - - - - - - 1 2
+ *      H2 E1 B1               - 1 - - 1 - 1 2
+ *      F2 E1 B1 A2            2 1 - - 1 2 1 2
+ *      E3 B1 A2               2 1 - - 3 2 1 2
+ *      B1 A2                  2 1 - - 3 2 1 2
+ *      C1 A2                  2 1 1 - 3 2 1 2
+ *      D1 A2                  2 1 1 1 3 2 1 2
+ *      A2                     2 1 1 1 3 2 1 2
+ *      B3                     2 3 1 1 3 2 1 2
+ *      C7                     2 3 7 1 3 2 1 2
+ *
+ * At this point, unfortunately, everybody in the list is
+ * uninteresting, so we fail to complete the following two
+ * steps to fully marking uninteresting commits.
+ *
+ *      D7                     2 3 7 7 3 2 1 2
+ *      E7                     2 3 7 7 7 2 1 2
+ *
+ * and we end up showing E as an interesting merge base.
  */
 
-static struct commit *common_ancestor(struct commit *rev1, struct commit *rev2)
+static int show_all = 0;
+
+static void mark_reachable_commits(struct commit_list *result,
+                                  struct commit_list *list)
+{
+       struct commit_list *tmp;
+
+       /*
+        * Postprocess to fully contaminate the well.
+        */
+       for (tmp = result; tmp; tmp = tmp->next) {
+               struct commit *c = tmp->item;
+               /* Reinject uninteresting ones to list,
+                * so we can scan their parents.
+                */
+               if (c->object.flags & UNINTERESTING)
+                       commit_list_insert(c, &list);
+       }
+       while (list) {
+               struct commit *c = list->item;
+               struct commit_list *parents;
+
+               tmp = list;
+               list = list->next;
+               free(tmp);
+
+               /* Anything taken out of the list is uninteresting, so
+                * mark all its parents uninteresting.  We do not
+                * parse new ones (we already parsed all the relevant
+                * ones).
+                */
+               parents = c->parents;
+               while (parents) {
+                       struct commit *p = parents->item;
+                       parents = parents->next;
+                       if (!(p->object.flags & UNINTERESTING)) {
+                               p->object.flags |= UNINTERESTING;
+                               commit_list_insert(p, &list);
+                       }
+               }
+       }
+}
+
+static int merge_base(struct commit *rev1, struct commit *rev2)
 {
        struct commit_list *list = NULL;
        struct commit_list *result = NULL;
+       struct commit_list *tmp = NULL;
 
-       if (rev1 == rev2)
-               return rev1;
+       if (rev1 == rev2) {
+               printf("%s\n", sha1_to_hex(rev1->object.sha1));
+               return 0;
+       }
 
        parse_commit(rev1);
        parse_commit(rev2);
@@ -100,15 +185,16 @@ static struct commit *common_ancestor(struct commit *rev1, struct commit *rev2)
 
        while (interesting(list)) {
                struct commit *commit = list->item;
-               struct commit_list *tmp = list, *parents;
+               struct commit_list *parents;
                int flags = commit->object.flags & 7;
 
+               tmp = list;
                list = list->next;
                free(tmp);
                if (flags == 3) {
                        insert_by_date(commit, &result);
 
-                       /* Mark children of a found merge uninteresting */
+                       /* Mark parents of a found merge uninteresting */
                        flags |= UNINTERESTING;
                }
                parents = commit->parents;
@@ -122,26 +208,52 @@ static struct commit *common_ancestor(struct commit *rev1, struct commit *rev2)
                        insert_by_date(p, &list);
                }
        }
-       return interesting(result);
+
+       if (!result)
+               return 1;
+
+       if (result->next && list)
+               mark_reachable_commits(result, list);
+
+       while (result) {
+               struct commit *commit = result->item;
+               result = result->next;
+               if (commit->object.flags & UNINTERESTING)
+                       continue;
+               printf("%s\n", sha1_to_hex(commit->object.sha1));
+               if (!show_all)
+                       return 0;
+               commit->object.flags |= UNINTERESTING;
+       }
+       return 0;
 }
 
+static const char merge_base_usage[] =
+"git-merge-base [--all] <commit-id> <commit-id>";
+
 int main(int argc, char **argv)
 {
-       struct commit *rev1, *rev2, *ret;
+       struct commit *rev1, *rev2;
        unsigned char rev1key[20], rev2key[20];
 
+       setup_git_directory();
+       git_config(git_default_config);
+
+       while (1 < argc && argv[1][0] == '-') {
+               char *arg = argv[1];
+               if (!strcmp(arg, "-a") || !strcmp(arg, "--all"))
+                       show_all = 1;
+               else
+                       usage(merge_base_usage);
+               argc--; argv++;
+       }
        if (argc != 3 ||
            get_sha1(argv[1], rev1key) ||
-           get_sha1(argv[2], rev2key)) {
-               usage("git-merge-base <commit-id> <commit-id>");
-       }
+           get_sha1(argv[2], rev2key))
+               usage(merge_base_usage);
        rev1 = lookup_commit_reference(rev1key);
        rev2 = lookup_commit_reference(rev2key);
        if (!rev1 || !rev2)
                return 1;
-       ret = common_ancestor(rev1, rev2);
-       if (!ret)
-               return 1;
-       printf("%s\n", sha1_to_hex(ret->object.sha1));
-       return 0;
+       return merge_base(rev1, rev2);
 }