Revision ae5d8470f6b8e1abdef19bf033472c63fb72b735 authored by Marco Roeland on 05 April 2006, 20:28:28 UTC, committed by Junio C Hamano on 05 April 2006, 21:07:21 UTC
The "--amend" option is used to amend the tip of the current branch. This documentation text was copied straight from the commit that implemented it. Some minor format tweaks for asciidoc were taken from work by Francis Daly in commit b0d08a5.. It looks good now also in the html page. [jc: amended further to follow the recommendation by Francis in commit 3070b60]. Signed-off-by: Marco Roeland <marco.roeland@xs4all.nl> Signed-off-by: Junio C Hamano <junkio@cox.net>
1 parent 3ffe0c2
merge-base.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.
*
*
* 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;
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));
return 0;
}
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 *parents;
int flags = commit->object.flags & 7;
tmp = list;
list = list->next;
free(tmp);
if (flags == 3) {
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 1;
if (result->next && list)
mark_reachable_commits(result, list);
while (result) {
struct commit *commit = result->item;
result = result->next;
if (commit->object.flags & UNINTERESTING)
continue;
printf("%s\n", sha1_to_hex(commit->object.sha1));
if (!show_all)
return 0;
commit->object.flags |= UNINTERESTING;
}
return 0;
}
static const char merge_base_usage[] =
"git-merge-base [--all] <commit-id> <commit-id>";
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"))
show_all = 1;
else
usage(merge_base_usage);
argc--; argv++;
}
if (argc != 3 ||
get_sha1(argv[1], rev1key) ||
get_sha1(argv[2], rev2key))
usage(merge_base_usage);
rev1 = lookup_commit_reference(rev1key);
rev2 = lookup_commit_reference(rev2key);
if (!rev1 || !rev2)
return 1;
return merge_base(rev1, rev2);
}
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