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merge-base: fully contaminate the well. 

The discussion on the list demonstrated a pathological case where
an ancestor of a merge-base can be left interesting.  This commit
introduces a postprocessing phase to fix it.

Signed-off-by: Junio C Hamano <junkio@cox.net>
maint
Junio C Hamano 2005-11-10 17:21:54 -08:00
parent 592ee97d8f
commit ed9a540b2b
1 changed files with 77 additions and 1 deletions
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78
merge-base.c
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@ -80,6 +80,45 @@ 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 int show_all = 0;
@ -88,6 +127,7 @@ 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 +144,10 @@ 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 +171,41 @@ static int merge_base(struct commit *rev1, struct commit *rev2)
if (!result)
return 1;

/*
* 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);
}
}
}

while (result) {
struct commit *commit = result->item;
result = result->next;