git-tar-tree: no more void pointer arithmetic

[git.git] / merge-base.c

diff --git a/merge-base.c b/merge-base.c
index 286bf0e..4856ca0 100644 (file)
--- a/merge-base.c
+++ b/merge-base.c
@@ -80,14 +80,98 @@ 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 used to fail to mark an
+ * ancestor of a merge base as UNINTERESTING before we introduced the
+ * postprocessing phase (mark_reachable_commits).
+ *
+ *               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 ended up showing E as an interesting merge base.
+ * The postprocessing phase re-injects C and continues traversal
+ * to contaminate D and E.
  */
 
 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) {
                printf("%s\n", sha1_to_hex(rev1->object.sha1));
@@ -104,9 +188,10 @@ static int merge_base(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) {
@@ -130,6 +215,9 @@ static int merge_base(struct commit *rev1, struct commit *rev2)
        if (!result)
                return 1;
 
+       if (result->next && list)
+               mark_reachable_commits(result, list);
+
        while (result) {
                struct commit *commit = result->item;
                result = result->next;
@@ -151,6 +239,9 @@ int main(int argc, char **argv)
        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"))
@@ -159,10 +250,12 @@ int main(int argc, char **argv)
                        usage(merge_base_usage);
                argc--; argv++;
        }
-       if (argc != 3 ||
-           get_sha1(argv[1], rev1key) ||
-           get_sha1(argv[2], rev2key))
+       if (argc != 3)
                usage(merge_base_usage);
+       if (get_sha1(argv[1], rev1key))
+               die("Not a valid object name %s", argv[1]);
+       if (get_sha1(argv[2], rev2key))
+               die("Not a valid object name %s", argv[2]);
        rev1 = lookup_commit_reference(rev1key);
        rev2 = lookup_commit_reference(rev2key);
        if (!rev1 || !rev2)