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authorJohannes Schindelin <Johannes.Schindelin@gmx.de>2006-06-29 15:17:32 +0200
committerJunio C Hamano <junkio@cox.net>2006-06-29 13:50:46 -0700
commit7c6f8aaf6d795f0c9a75671acceb9754ea06fd81 (patch)
tree5439b959adc9ff216174c6bc84fd54cc591c5d0d /commit.c
parent52cab8a0848463d793a3fc819b6d604ffc077ac1 (diff)
downloadgit-7c6f8aaf6d795f0c9a75671acceb9754ea06fd81.tar.gz
move get_merge_bases() to core lib.
Signed-off-by: Junio C Hamano <junkio@cox.net>
Diffstat (limited to 'commit.c')
-rw-r--r--commit.c240
1 files changed, 240 insertions, 0 deletions
diff --git a/commit.c b/commit.c
index e51ffa1c6c..0431027ef2 100644
--- a/commit.c
+++ b/commit.c
@@ -846,3 +846,243 @@ void sort_in_topological_order_fn(struct commit_list ** list, int lifo,
}
free(nodes);
}
+
+/* merge-rebase stuff */
+
+#define PARENT1 1
+#define PARENT2 2
+#define UNINTERESTING 4
+
+static struct commit *interesting(struct commit_list *list)
+{
+ while (list) {
+ struct commit *commit = list->item;
+ list = list->next;
+ if (commit->object.flags & UNINTERESTING)
+ continue;
+ return commit;
+ }
+ return NULL;
+}
+
+/*
+ * A pathological example of how this thing works.
+ *
+ * Suppose we had this commit graph, where chronologically
+ * the timestamp on the commit are A <= B <= C <= D <= E <= F
+ * and we are trying to figure out the merge base for E and F
+ * commits.
+ *
+ * F
+ * / \
+ * E A D
+ * \ / /
+ * B /
+ * \ /
+ * C
+ *
+ * First we push E and F to list to be processed. E gets bit 1
+ * and F gets bit 2. The list becomes:
+ *
+ * list=F(2) E(1), result=empty
+ *
+ * Then we pop F, the newest commit, from the list. Its flag is 2.
+ * We scan its parents, mark them reachable from the side that F is
+ * reachable from, and push them to the list:
+ *
+ * list=E(1) D(2) A(2), result=empty
+ *
+ * Next pop E and do the same.
+ *
+ * list=D(2) B(1) A(2), result=empty
+ *
+ * Next pop D and do the same.
+ *
+ * list=C(2) B(1) A(2), result=empty
+ *
+ * Next pop C and do the same.
+ *
+ * list=B(1) A(2), result=empty
+ *
+ * Now it is B's turn. We mark its parent, C, reachable from B's side,
+ * and push it to the list:
+ *
+ * list=C(3) A(2), result=empty
+ *
+ * Now pop C and notice it has flags==3. It is placed on the result list,
+ * and the list now contains:
+ *
+ * list=A(2), result=C(3)
+ *
+ * We pop A and do the same.
+ *
+ * list=B(3), result=C(3)
+ *
+ * Next, we pop B and something very interesting happens. It has flags==3
+ * so it is also placed on the result list, and its parents are marked
+ * uninteresting, retroactively, and placed back on the list:
+ *
+ * list=C(7), result=C(7) B(3)
+ *
+ * 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 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);
+ }
+ }
+ }
+}
+
+struct commit_list *get_merge_bases(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 commit_list_insert(rev1, &result);
+
+ parse_commit(rev1);
+ parse_commit(rev2);
+
+ rev1->object.flags |= PARENT1;
+ rev2->object.flags |= PARENT2;
+ insert_by_date(rev1, &list);
+ insert_by_date(rev2, &list);
+
+ while (interesting(list)) {
+ struct commit *commit = list->item;
+ struct commit_list *parents;
+ int flags = commit->object.flags
+ & (PARENT1 | PARENT2 | UNINTERESTING);
+
+ tmp = list;
+ list = list->next;
+ free(tmp);
+ if (flags == (PARENT1 | PARENT2)) {
+ insert_by_date(commit, &result);
+
+ /* Mark parents of a found merge uninteresting */
+ flags |= UNINTERESTING;
+ }
+ parents = commit->parents;
+ while (parents) {
+ struct commit *p = parents->item;
+ parents = parents->next;
+ if ((p->object.flags & flags) == flags)
+ continue;
+ parse_commit(p);
+ p->object.flags |= flags;
+ insert_by_date(p, &list);
+ }
+ }
+
+ if (!result)
+ return NULL;
+
+ if (result->next && list)
+ mark_reachable_commits(result, list);
+
+ /* cull duplicates */
+ for (tmp = result, list = NULL; tmp; ) {
+ struct commit *commit = tmp->item;
+ struct commit_list *next = tmp->next;
+ if (commit->object.flags & UNINTERESTING) {
+ if (list != NULL)
+ list->next = next;
+ free(tmp);
+ } else {
+ if (list == NULL)
+ result = tmp;
+ list = tmp;
+ commit->object.flags |= UNINTERESTING;
+ }
+
+ tmp = next;
+ }
+
+ /* reset flags */
+ clear_commit_marks(rev1, PARENT1 | PARENT2 | UNINTERESTING);
+ clear_commit_marks(rev2, PARENT1 | PARENT2 | UNINTERESTING);
+
+ return result;
+}