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Merge branch 'jc/merge-bases'

Browse Source 
Optimise the "merge-base" computation a bit, and also update its
users that do not need the full merge-base information to call a
cheaper subset.

* jc/merge-bases:
  reduce_heads(): reimplement on top of remove_redundant()
  merge-base: "--is-ancestor A B"
  get_merge_bases_many(): walk from many tips in parallel
  in_merge_bases(): use paint_down_to_common()
  merge_bases_many(): split out the logic to paint history
  in_merge_bases(): omit unnecessary redundant common ancestor reduction
  http-push: use in_merge_bases() for fast-forward check
  receive-pack: use in_merge_bases() for fast-forward check
  in_merge_bases(): support only one "other" commit
This commit is contained in:
Junio C Hamano 2012-09-11 11:35:26 -07:00
commit 34f5130af8
11 changed files with 185 additions and 113 deletions
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28
Documentation/git-merge-base.txt
View File

@ -11,6 +11,7 @@ SYNOPSIS
[verse]
'git merge-base' [-a|--all] <commit> <commit>...
'git merge-base' [-a|--all] --octopus <commit>...
'git merge-base' --is-ancestor <commit> <commit>
'git merge-base' --independent <commit>...
DESCRIPTION
@ -50,6 +51,12 @@ from linkgit:git-show-branch[1] when used with the `--merge-base` option.
from any other. This mimics the behavior of 'git show-branch
--independent'.
--is-ancestor::
Check if the first <commit> is an ancestor of the second <commit>,
and exit with status 0 if true, or with status 1 if not.
Errors are signaled by a non-zero status that is not 1.
OPTIONS
-------
-a::
@ -110,6 +117,27 @@ both '1' and '2' are merge-bases of A and B. Neither one is better than
the other (both are 'best' merge bases). When the `--all` option is not given,
it is unspecified which best one is output.
A common idiom to check "fast-forward-ness" between two commits A
and B is (or at least used to be) to compute the merge base between
A and B, and check if it is the same as A, in which case, A is an
ancestor of B. You will see this idiom used often in older scripts.
A=$(git rev-parse --verify A)
if test "$A" = "$(git merge-base A B)"
then
... A is an ancestor of B ...
fi
In modern git, you can say this in a more direct way:
if git merge-base --is-ancestor A B
then
... A is an ancestor of B ...
fi
instead.
See also
--------
linkgit:git-rev-list[1],

4
builtin/branch.c
View File

@ -130,7 +130,7 @@ static int branch_merged(int kind, const char *name,
if (!reference_rev)
reference_rev = head_rev;
merged = in_merge_bases(rev, &reference_rev, 1);
merged = in_merge_bases(rev, reference_rev);
/*
* After the safety valve is fully redefined to "check with
@ -140,7 +140,7 @@ static int branch_merged(int kind, const char *name,
* a gentle reminder is in order.
*/
if ((head_rev != reference_rev) &&
in_merge_bases(rev, &head_rev, 1) != merged) {
in_merge_bases(rev, head_rev) != merged) {
if (merged)
warning(_("deleting branch '%s' that has been merged to\n"
" '%s', but not yet merged to HEAD."),

2
builtin/fetch.c
View File

@ -323,7 +323,7 @@ static int update_local_ref(struct ref *ref,
return r;
}
if (in_merge_bases(current, &updated, 1)) {
if (in_merge_bases(current, updated)) {
char quickref[83];
int r;
strcpy(quickref, find_unique_abbrev(current->object.sha1, DEFAULT_ABBREV));

22
builtin/merge-base.c
View File

@ -26,6 +26,7 @@ static const char * const merge_base_usage[] = {
N_("git merge-base [-a|--all] <commit> <commit>..."),
N_("git merge-base [-a|--all] --octopus <commit>..."),
N_("git merge-base --independent <commit>..."),
N_("git merge-base --is-ancestor <commit> <commit>"),
NULL
};
@ -70,6 +71,20 @@ static int handle_octopus(int count, const char **args, int reduce, int show_all
return 0;
}
static int handle_is_ancestor(int argc, const char **argv)
{
struct commit *one, *two;
if (argc != 2)
die("--is-ancestor takes exactly two commits");
one = get_commit_reference(argv[0]);
two = get_commit_reference(argv[1]);
if (in_merge_bases(one, two))
return 0;
else
return 1;
}
int cmd_merge_base(int argc, const char **argv, const char *prefix)
{
struct commit **rev;
@ -77,11 +92,14 @@ int cmd_merge_base(int argc, const char **argv, const char *prefix)
int show_all = 0;
int octopus = 0;
int reduce = 0;
int is_ancestor = 0;
struct option options[] = {
OPT_BOOLEAN('a', "all", &show_all, N_("output all common ancestors")),
OPT_BOOLEAN(0, "octopus", &octopus, N_("find ancestors for a single n-way merge")),
OPT_BOOLEAN(0, "independent", &reduce, N_("list revs not reachable from others")),
OPT_BOOLEAN(0, "is-ancestor", &is_ancestor,
N_("is the first one ancestor of the other?")),
OPT_END()
};
@ -89,6 +107,10 @@ int cmd_merge_base(int argc, const char **argv, const char *prefix)
argc = parse_options(argc, argv, prefix, options, merge_base_usage, 0);
if (!octopus && !reduce && argc < 2)
usage_with_options(merge_base_usage, options);
if (is_ancestor && (show_all | octopus | reduce))
die("--is-ancestor cannot be used with other options");
if (is_ancestor)
return handle_is_ancestor(argc, argv);
if (reduce && (show_all || octopus))
die("--independent cannot be used with other options");

8
builtin/receive-pack.c
View File

@ -480,7 +480,6 @@ static const char *update(struct command *cmd)
!prefixcmp(name, "refs/heads/")) {
struct object *old_object, *new_object;
struct commit *old_commit, *new_commit;
struct commit_list *bases, *ent;
old_object = parse_object(old_sha1);
new_object = parse_object(new_sha1);
@ -493,12 +492,7 @@ static const char *update(struct command *cmd)
}
old_commit = (struct commit *)old_object;
new_commit = (struct commit *)new_object;
bases = get_merge_bases(old_commit, new_commit, 1);
for (ent = bases; ent; ent = ent->next)
if (!hashcmp(old_sha1, ent->item->object.sha1))
break;
free_commit_list(bases);
if (!ent) {
if (!in_merge_bases(old_commit, new_commit)) {
rp_error("denying non-fast-forward %s"
" (you should pull first)", name);
return "non-fast-forward";

213
commit.c
View File

@ -607,28 +607,12 @@ static struct commit *interesting(struct commit_list *list)
return NULL;
}
static struct commit_list *merge_bases_many(struct commit *one, int n, struct commit **twos)
static struct commit_list *paint_down_to_common(struct commit *one, int n, struct commit **twos)
{
struct commit_list *list = NULL;
struct commit_list *result = NULL;
int i;
for (i = 0; i < n; i++) {
if (one == twos[i])
/*
* We do not mark this even with RESULT so we do not
* have to clean it up.
*/
return commit_list_insert(one, &result);
}
if (parse_commit(one))
return NULL;
for (i = 0; i < n; i++) {
if (parse_commit(twos[i]))
return NULL;
}
one->object.flags |= PARENT1;
commit_list_insert_by_date(one, &list);
for (i = 0; i < n; i++) {
@ -669,9 +653,34 @@ static struct commit_list *merge_bases_many(struct commit *one, int n, struct co
}
}
/* Clean up the result to remove stale ones */
free_commit_list(list);
list = result; result = NULL;
return result;
}
static struct commit_list *merge_bases_many(struct commit *one, int n, struct commit **twos)
{
struct commit_list *list = NULL;
struct commit_list *result = NULL;
int i;
for (i = 0; i < n; i++) {
if (one == twos[i])
/*
* We do not mark this even with RESULT so we do not
* have to clean it up.
*/
return commit_list_insert(one, &result);
}
if (parse_commit(one))
return NULL;
for (i = 0; i < n; i++) {
if (parse_commit(twos[i]))
return NULL;
}
list = paint_down_to_common(one, n, twos);
while (list) {
struct commit_list *next = list->next;
if (!(list->item->object.flags & STALE))
@ -709,6 +718,60 @@ struct commit_list *get_octopus_merge_bases(struct commit_list *in)
return ret;
}
static int remove_redundant(struct commit **array, int cnt)
{
/*
* Some commit in the array may be an ancestor of
* another commit. Move such commit to the end of
* the array, and return the number of commits that
* are independent from each other.
*/
struct commit **work;
unsigned char *redundant;
int *filled_index;
int i, j, filled;
work = xcalloc(cnt, sizeof(*work));
redundant = xcalloc(cnt, 1);
filled_index = xmalloc(sizeof(*filled_index) * (cnt - 1));
for (i = 0; i < cnt; i++) {
struct commit_list *common;
if (redundant[i])
continue;
for (j = filled = 0; j < cnt; j++) {
if (i == j || redundant[j])
continue;
filled_index[filled] = j;
work[filled++] = array[j];
}
common = paint_down_to_common(array[i], filled, work);
if (array[i]->object.flags & PARENT2)
redundant[i] = 1;
for (j = 0; j < filled; j++)
if (work[j]->object.flags & PARENT1)
redundant[filled_index[j]] = 1;
clear_commit_marks(array[i], all_flags);
for (j = 0; j < filled; j++)
clear_commit_marks(work[j], all_flags);
free_commit_list(common);
}
/* Now collect the result */
memcpy(work, array, sizeof(*array) * cnt);
for (i = filled = 0; i < cnt; i++)
if (!redundant[i])
array[filled++] = work[i];
for (j = filled, i = 0; i < cnt; i++)
if (redundant[i])
array[j++] = work[i];
free(work);
free(redundant);
free(filled_index);
return filled;
}
struct commit_list *get_merge_bases_many(struct commit *one,
int n,
struct commit **twos,
@ -717,7 +780,7 @@ struct commit_list *get_merge_bases_many(struct commit *one,
struct commit_list *list;
struct commit **rslt;
struct commit_list *result;
int cnt, i, j;
int cnt, i;
result = merge_bases_many(one, n, twos);
for (i = 0; i < n; i++) {
@ -748,28 +811,11 @@ struct commit_list *get_merge_bases_many(struct commit *one,
clear_commit_marks(one, all_flags);
for (i = 0; i < n; i++)
clear_commit_marks(twos[i], all_flags);
for (i = 0; i < cnt - 1; i++) {
for (j = i+1; j < cnt; j++) {
if (!rslt[i] || !rslt[j])
continue;
result = merge_bases_many(rslt[i], 1, &rslt[j]);
clear_commit_marks(rslt[i], all_flags);
clear_commit_marks(rslt[j], all_flags);
for (list = result; list; list = list->next) {
if (rslt[i] == list->item)
rslt[i] = NULL;
if (rslt[j] == list->item)
rslt[j] = NULL;
}
}
}
/* Surviving ones in rslt[] are the independent results */
cnt = remove_redundant(rslt, cnt);
result = NULL;
for (i = 0; i < cnt; i++) {
if (rslt[i])
commit_list_insert_by_date(rslt[i], &result);
}
for (i = 0; i < cnt; i++)
commit_list_insert_by_date(rslt[i], &result);
free(rslt);
return result;
}
@ -780,6 +826,9 @@ struct commit_list *get_merge_bases(struct commit *one, struct commit *two,
return get_merge_bases_many(one, 1, &two, cleanup);
}
/*
* Is "commit" a decendant of one of the elements on the "with_commit" list?
*/
int is_descendant_of(struct commit *commit, struct commit_list *with_commit)
{
if (!with_commit)
@ -789,28 +838,28 @@ int is_descendant_of(struct commit *commit, struct commit_list *with_commit)
other = with_commit->item;
with_commit = with_commit->next;
if (in_merge_bases(other, &commit, 1))
if (in_merge_bases(other, commit))
return 1;
}
return 0;
}
int in_merge_bases(struct commit *commit, struct commit **reference, int num)
/*
* Is "commit" an ancestor of (i.e. reachable from) the "reference"?
*/
int in_merge_bases(struct commit *commit, struct commit *reference)
{
struct commit_list *bases, *b;
struct commit_list *bases;
int ret = 0;
if (num == 1)
bases = get_merge_bases(commit, *reference, 1);
else
die("not yet");
for (b = bases; b; b = b->next) {
if (!hashcmp(commit->object.sha1, b->item->object.sha1)) {
ret = 1;
break;
}
}
if (parse_commit(commit) || parse_commit(reference))
return ret;
bases = paint_down_to_common(commit, 1, &reference);
if (commit->object.flags & PARENT2)
ret = 1;
clear_commit_marks(commit, all_flags);
clear_commit_marks(reference, all_flags);
free_commit_list(bases);
return ret;
}
@ -819,51 +868,31 @@ struct commit_list *reduce_heads(struct commit_list *heads)
{
struct commit_list *p;
struct commit_list *result = NULL, **tail = &result;
struct commit **other;
size_t num_head, num_other;
struct commit **array;
int num_head, i;
if (!heads)
return NULL;
/* Avoid unnecessary reallocations */
for (p = heads, num_head = 0; p; p = p->next)
num_head++;
other = xcalloc(sizeof(*other), num_head);
/* For each commit, see if it can be reached by others */
for (p = heads; p; p = p->next) {
struct commit_list *q, *base;
/* Do we already have this in the result? */
for (q = result; q; q = q->next)
if (p->item == q->item)
break;
if (q)
/* Uniquify */
for (p = heads; p; p = p->next)
p->item->object.flags &= ~STALE;
for (p = heads, num_head = 0; p; p = p->next) {
if (p->item->object.flags & STALE)
continue;
num_other = 0;
for (q = heads; q; q = q->next) {
if (p->item == q->item)
continue;
other[num_other++] = q->item;
}
if (num_other)
base = get_merge_bases_many(p->item, num_other, other, 1);
else
base = NULL;
/*
* If p->item does not have anything common with other
* commits, there won't be any merge base. If it is
* reachable from some of the others, p->item will be
* the merge base. If its history is connected with
* others, but p->item is not reachable by others, we
* will get something other than p->item back.
*/
if (!base || (base->item != p->item))
tail = &(commit_list_insert(p->item, tail)->next);
free_commit_list(base);
p->item->object.flags |= STALE;
num_head++;
}
free(other);
array = xcalloc(sizeof(*array), num_head);
for (p = heads, i = 0; p; p = p->next) {
if (p->item->object.flags & STALE) {
array[i++] = p->item;
p->item->object.flags &= ~STALE;
}
}
num_head = remove_redundant(array, num_head);
for (i = 0; i < num_head; i++)
tail = &commit_list_insert(array[i], tail)->next;
return result;
}

2
commit.h
View File

@ -171,7 +171,7 @@ extern struct commit_list *get_shallow_commits(struct object_array *heads,
int depth, int shallow_flag, int not_shallow_flag);
int is_descendant_of(struct commit *, struct commit_list *);
int in_merge_bases(struct commit *, struct commit **, int);
int in_merge_bases(struct commit *, struct commit *);
extern int interactive_add(int argc, const char **argv, const char *prefix, int patch);
extern int run_add_interactive(const char *revision, const char *patch_mode,

2
contrib/examples/builtin-fetch--tool.c
View File

@ -96,7 +96,7 @@ static int update_local_ref(const char *name,
strcpy(oldh, find_unique_abbrev(current->object.sha1, DEFAULT_ABBREV));
strcpy(newh, find_unique_abbrev(sha1_new, DEFAULT_ABBREV));
if (in_merge_bases(current, &updated, 1)) {
if (in_merge_bases(current, updated)) {
fprintf(stderr, "* %s: fast-forward to %s\n",
name, note);
fprintf(stderr, " old..new: %s..%s\n", oldh, newh);

2
fast-import.c
View File

@ -1691,7 +1691,7 @@ static int update_branch(struct branch *b)
return error("Branch %s is missing commits.", b->name);
}
if (!in_merge_bases(old_cmit, &new_cmit, 1)) {
if (!in_merge_bases(old_cmit, new_cmit)) {
unlock_ref(lock);
warning("Not updating %s"
" (new tip %s does not contain %s)",

3
http-push.c
View File

@ -1610,9 +1610,8 @@ static int verify_merge_base(unsigned char *head_sha1, struct ref *remote)
{
struct commit *head = lookup_commit_or_die(head_sha1, "HEAD");
struct commit *branch = lookup_commit_or_die(remote->old_sha1, remote->name);
struct commit_list *merge_bases = get_merge_bases(head, branch, 1);
return (merge_bases && !merge_bases->next && merge_bases->item == branch);
return in_merge_bases(branch, head);
}
static int delete_remote_branch(const char *pattern, int force)

12
submodule.c
View File

@ -788,7 +788,7 @@ static int find_first_merges(struct object_array *result, const char *path,
die("revision walk setup failed");
while ((commit = get_revision(&revs)) != NULL) {
struct object *o = &(commit->object);
if (in_merge_bases(b, &commit, 1))
if (in_merge_bases(b, commit))
add_object_array(o, NULL, &merges);
}
reset_revision_walk();
@ -803,7 +803,7 @@ static int find_first_merges(struct object_array *result, const char *path,
contains_another = 0;
for (j = 0; j < merges.nr; j++) {
struct commit *m2 = (struct commit *) merges.objects[j].item;
if (i != j && in_merge_bases(m2, &m1, 1)) {
if (i != j && in_merge_bases(m2, m1)) {
contains_another = 1;
break;
}
@ -865,18 +865,18 @@ int merge_submodule(unsigned char result[20], const char *path,
}
/* check whether both changes are forward */
if (!in_merge_bases(commit_base, &commit_a, 1) ||
!in_merge_bases(commit_base, &commit_b, 1)) {
if (!in_merge_bases(commit_base, commit_a) ||
!in_merge_bases(commit_base, commit_b)) {
MERGE_WARNING(path, "commits don't follow merge-base");
return 0;
}
/* Case #1: a is contained in b or vice versa */
if (in_merge_bases(commit_a, &commit_b, 1)) {
if (in_merge_bases(commit_a, commit_b)) {
hashcpy(result, b);
return 1;
}
if (in_merge_bases(commit_b, &commit_a, 1)) {
if (in_merge_bases(commit_b, commit_a)) {
hashcpy(result, a);
return 1;
}