Merge branch 'js/merge-base'
* js/merge-base: Additional merge-base tests (revised) merge-base: update the clean-up postprocessing
This commit is contained in:
Junio C Hamano
commit
e40e0135f2
290
commit.c
290
commit.c
@ -854,6 +854,7 @@ void sort_in_topological_order_fn(struct commit_list ** list, int lifo,
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#define PARENT1 (1u<< 8)
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#define PARENT2 (1u<< 9)
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#define STALE (1u<<10)
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#define RESULT (1u<<11)
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static struct commit *interesting(struct commit_list *list)
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{
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@ -867,183 +868,42 @@ static struct commit *interesting(struct commit_list *list)
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return NULL;
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}
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/*
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* A pathological example of how this thing works.
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*
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* Suppose we had this commit graph, where chronologically
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* the timestamp on the commit are A <= B <= C <= D <= E <= F
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* and we are trying to figure out the merge base for E and F
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* commits.
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*
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* F
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* / \
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* E A D
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* \ / /
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* B /
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* \ /
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* C
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*
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* First we push E and F to list to be processed. E gets bit 1
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* and F gets bit 2. The list becomes:
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*
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* list=F(2) E(1), result=empty
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*
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* Then we pop F, the newest commit, from the list. Its flag is 2.
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* We scan its parents, mark them reachable from the side that F is
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* reachable from, and push them to the list:
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*
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* list=E(1) D(2) A(2), result=empty
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*
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* Next pop E and do the same.
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*
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* list=D(2) B(1) A(2), result=empty
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*
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* Next pop D and do the same.
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*
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* list=C(2) B(1) A(2), result=empty
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*
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* Next pop C and do the same.
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*
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* list=B(1) A(2), result=empty
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*
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* Now it is B's turn. We mark its parent, C, reachable from B's side,
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* and push it to the list:
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*
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* list=C(3) A(2), result=empty
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*
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* Now pop C and notice it has flags==3. It is placed on the result list,
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* and the list now contains:
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*
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* list=A(2), result=C(3)
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*
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* We pop A and do the same.
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*
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* list=B(3), result=C(3)
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*
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* Next, we pop B and something very interesting happens. It has flags==3
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* so it is also placed on the result list, and its parents are marked
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* stale, retroactively, and placed back on the list:
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*
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* list=C(7), result=C(7) B(3)
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*
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* Now, list does not have any interesting commit. So we find the newest
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* commit from the result list that is not marked stale. Which is
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* commit B.
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*
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*
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* Another pathological example how this thing used to fail to mark an
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* ancestor of a merge base as STALE before we introduced the
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* postprocessing phase (mark_reachable_commits).
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*
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* 2
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* H
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* 1 / \
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* G A \
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* |\ / \
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* | B \
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* | \ \
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* \ C F
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* \ \ /
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* \ D /
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* \ | /
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* \| /
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* E
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*
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* list A B C D E F G H
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* G1 H2 - - - - - - 1 2
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* H2 E1 B1 - 1 - - 1 - 1 2
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* F2 E1 B1 A2 2 1 - - 1 2 1 2
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* E3 B1 A2 2 1 - - 3 2 1 2
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* B1 A2 2 1 - - 3 2 1 2
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* C1 A2 2 1 1 - 3 2 1 2
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* D1 A2 2 1 1 1 3 2 1 2
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* A2 2 1 1 1 3 2 1 2
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* B3 2 3 1 1 3 2 1 2
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* C7 2 3 7 1 3 2 1 2
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*
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* At this point, unfortunately, everybody in the list is
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* stale, so we fail to complete the following two
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* steps to fully marking stale commits.
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*
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* D7 2 3 7 7 3 2 1 2
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* E7 2 3 7 7 7 2 1 2
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*
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* and we ended up showing E as an interesting merge base.
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* The postprocessing phase re-injects C and continues traversal
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* to contaminate D and E.
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*/
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static void mark_reachable_commits(struct commit_list *result,
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struct commit_list *list)
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{
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struct commit_list *tmp;
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/*
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* Postprocess to fully contaminate the well.
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*/
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for (tmp = result; tmp; tmp = tmp->next) {
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struct commit *c = tmp->item;
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/* Reinject stale ones to list,
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* so we can scan their parents.
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*/
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if (c->object.flags & STALE)
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commit_list_insert(c, &list);
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}
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while (list) {
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struct commit *c = list->item;
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struct commit_list *parents;
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tmp = list;
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list = list->next;
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free(tmp);
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/* Anything taken out of the list is stale, so
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* mark all its parents stale. We do not
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* parse new ones (we already parsed all the relevant
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* ones).
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*/
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parents = c->parents;
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while (parents) {
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struct commit *p = parents->item;
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parents = parents->next;
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if (!(p->object.flags & STALE)) {
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p->object.flags |= STALE;
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commit_list_insert(p, &list);
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}
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}
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}
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}
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struct commit_list *get_merge_bases(struct commit *rev1, struct commit *rev2,
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int cleanup)
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static struct commit_list *merge_bases(struct commit *one, struct commit *two)
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{
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struct commit_list *list = NULL;
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struct commit_list *result = NULL;
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struct commit_list *tmp = NULL;
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if (rev1 == rev2)
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return commit_list_insert(rev1, &result);
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if (one == two)
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/* We do not mark this even with RESULT so we do not
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* have to clean it up.
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*/
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return commit_list_insert(one, &result);
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parse_commit(rev1);
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parse_commit(rev2);
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parse_commit(one);
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parse_commit(two);
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rev1->object.flags |= PARENT1;
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rev2->object.flags |= PARENT2;
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insert_by_date(rev1, &list);
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insert_by_date(rev2, &list);
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one->object.flags |= PARENT1;
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two->object.flags |= PARENT2;
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insert_by_date(one, &list);
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insert_by_date(two, &list);
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while (interesting(list)) {
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struct commit *commit = list->item;
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struct commit *commit;
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struct commit_list *parents;
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int flags = commit->object.flags
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& (PARENT1 | PARENT2 | STALE);
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struct commit_list *n;
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int flags;
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tmp = list;
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list = list->next;
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free(tmp);
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commit = list->item;
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n = list->next;
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free(list);
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list = n;
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flags = commit->object.flags & (PARENT1 | PARENT2 | STALE);
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if (flags == (PARENT1 | PARENT2)) {
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insert_by_date(commit, &result);
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if (!(commit->object.flags & RESULT)) {
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commit->object.flags |= RESULT;
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insert_by_date(commit, &result);
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}
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/* Mark parents of a found merge stale */
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flags |= STALE;
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}
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@ -1059,35 +919,75 @@ struct commit_list *get_merge_bases(struct commit *rev1, struct commit *rev2,
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}
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}
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if (!result)
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goto finish;
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if (result->next && list)
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mark_reachable_commits(result, list);
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/* cull duplicates */
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for (tmp = result, list = NULL; tmp; ) {
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struct commit *commit = tmp->item;
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struct commit_list *next = tmp->next;
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if (commit->object.flags & STALE) {
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if (list != NULL)
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list->next = next;
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free(tmp);
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} else {
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if (list == NULL)
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result = tmp;
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list = tmp;
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commit->object.flags |= STALE;
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}
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tmp = next;
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/* Clean up the result to remove stale ones */
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list = result; result = NULL;
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while (list) {
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struct commit_list *n = list->next;
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if (!(list->item->object.flags & STALE))
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insert_by_date(list->item, &result);
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free(list);
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list = n;
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}
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finish:
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if (cleanup) {
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clear_commit_marks(rev1, PARENT1 | PARENT2 | STALE);
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clear_commit_marks(rev2, PARENT1 | PARENT2 | STALE);
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}
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return result;
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}
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struct commit_list *get_merge_bases(struct commit *one,
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struct commit *two,
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int cleanup)
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{
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const unsigned all_flags = (PARENT1 | PARENT2 | STALE | RESULT);
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struct commit_list *list;
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struct commit **rslt;
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struct commit_list *result;
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int cnt, i, j;
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result = merge_bases(one, two);
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if (one == two)
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return result;
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if (!result || !result->next) {
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if (cleanup) {
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clear_commit_marks(one, all_flags);
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clear_commit_marks(two, all_flags);
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}
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return result;
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}
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/* There are more than one */
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cnt = 0;
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list = result;
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while (list) {
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list = list->next;
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cnt++;
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}
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rslt = xcalloc(cnt, sizeof(*rslt));
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for (list = result, i = 0; list; list = list->next)
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rslt[i++] = list->item;
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free_commit_list(result);
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clear_commit_marks(one, all_flags);
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clear_commit_marks(two, all_flags);
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for (i = 0; i < cnt - 1; i++) {
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for (j = i+1; j < cnt; j++) {
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if (!rslt[i] || !rslt[j])
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continue;
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result = merge_bases(rslt[i], rslt[j]);
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clear_commit_marks(rslt[i], all_flags);
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clear_commit_marks(rslt[j], all_flags);
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for (list = result; list; list = list->next) {
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if (rslt[i] == list->item)
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rslt[i] = NULL;
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if (rslt[j] == list->item)
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rslt[j] = NULL;
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}
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}
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}
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/* Surviving ones in rslt[] are the independent results */
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result = NULL;
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for (i = 0; i < cnt; i++) {
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if (rslt[i])
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insert_by_date(rslt[i], &result);
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}
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free(rslt);
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return result;
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}
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@ -44,6 +44,43 @@ A=$(doit 1 A $B)
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G=$(doit 7 G $B $E)
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H=$(doit 8 H $A $F)
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# Setup for second test to demonstrate that relying on timestamps in a
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# distributed SCM to provide a _consistent_ partial ordering of commits
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# leads to insanity.
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#
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# Relative
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# Structure timestamps
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#
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# PL PR +4 +4
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# / \/ \ / \/ \
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# L2 C2 R2 +3 -1 +3
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# | | | | | |
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# L1 C1 R1 +2 -2 +2
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# | | | | | |
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# L0 C0 R0 +1 -3 +1
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# \ | / \ | /
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# S 0
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#
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# The left and right chains of commits can be of any length and complexity as
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# long as all of the timestamps are greater than that of S.
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S=$(doit 0 S)
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C0=$(doit -3 C0 $S)
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C1=$(doit -2 C1 $C0)
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C2=$(doit -1 C2 $C1)
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L0=$(doit 1 L0 $S)
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L1=$(doit 2 L1 $L0)
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L2=$(doit 3 L2 $L1)
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R0=$(doit 1 R0 $S)
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R1=$(doit 2 R1 $R0)
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R2=$(doit 3 R2 $R1)
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PL=$(doit 4 PL $L2 $C2)
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PR=$(doit 4 PR $C2 $R2)
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test_expect_success 'compute merge-base (single)' \
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'MB=$(git-merge-base G H) &&
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expr "$(git-name-rev "$MB")" : "[0-9a-f]* tags/B"'
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@ -56,4 +93,12 @@ test_expect_success 'compute merge-base with show-branch' \
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'MB=$(git-show-branch --merge-base G H) &&
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expr "$(git-name-rev "$MB")" : "[0-9a-f]* tags/B"'
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test_expect_success 'compute merge-base (single)' \
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'MB=$(git-merge-base PL PR) &&
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expr "$(git-name-rev "$MB")" : "[0-9a-f]* tags/C2"'
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test_expect_success 'compute merge-base (all)' \
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'MB=$(git-merge-base --all PL PR) &&
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expr "$(git-name-rev "$MB")" : "[0-9a-f]* tags/C2"'
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test_done
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