зеркало из https://github.com/microsoft/git.git
148 строки
3.5 KiB
C
148 строки
3.5 KiB
C
#include <stdlib.h>
|
|
#include "cache.h"
|
|
#include "commit.h"
|
|
|
|
#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.
|
|
*/
|
|
|
|
static struct commit *common_ancestor(struct commit *rev1, struct commit *rev2)
|
|
{
|
|
struct commit_list *list = NULL;
|
|
struct commit_list *result = NULL;
|
|
|
|
if (rev1 == rev2)
|
|
return rev1;
|
|
|
|
parse_commit(rev1);
|
|
parse_commit(rev2);
|
|
|
|
rev1->object.flags |= 1;
|
|
rev2->object.flags |= 2;
|
|
insert_by_date(rev1, &list);
|
|
insert_by_date(rev2, &list);
|
|
|
|
while (interesting(list)) {
|
|
struct commit *commit = list->item;
|
|
struct commit_list *tmp = list, *parents;
|
|
int flags = commit->object.flags & 7;
|
|
|
|
list = list->next;
|
|
free(tmp);
|
|
if (flags == 3) {
|
|
insert_by_date(commit, &result);
|
|
|
|
/* Mark children 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);
|
|
}
|
|
}
|
|
return interesting(result);
|
|
}
|
|
|
|
int main(int argc, char **argv)
|
|
{
|
|
struct commit *rev1, *rev2, *ret;
|
|
unsigned char rev1key[20], rev2key[20];
|
|
|
|
if (argc != 3 ||
|
|
get_sha1(argv[1], rev1key) ||
|
|
get_sha1(argv[2], rev2key)) {
|
|
usage("git-merge-base <commit-id> <commit-id>");
|
|
}
|
|
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;
|
|
}
|