git/commit-reach.c
Abhishek Kumar 8d00d7c3df commit-reach: use corrected commit dates in paint_down_to_common()
091f4cf (commit: don't use generation numbers if not needed,
2018-08-30) changed paint_down_to_common() to use commit dates instead
of generation numbers v1 (topological levels) as the performance
regressed on certain topologies. With generation number v2 (corrected
commit dates) implemented, we no longer have to rely on commit dates and
can use generation numbers.

For example, the command `git merge-base v4.8 v4.9` on the Linux
repository walks 167468 commits, taking 0.135s for committer date and
167496 commits, taking 0.157s for corrected committer date respectively.

While using corrected commit dates, Git walks nearly the same number of
commits as commit date, the process is slower as for each comparision we
have to access a commit-slab (for corrected committer date) instead of
accessing struct member (for committer date).

This change incidentally broke the fragile t6404-recursive-merge test.
t6404-recursive-merge sets up a unique repository where all commits have
the same committer date without a well-defined merge-base.

While running tests with GIT_TEST_COMMIT_GRAPH unset, we use committer
date as a heuristic in paint_down_to_common(). 6404.1 'combined merge
conflicts' merges commits in the order:
- Merge C with B to form an intermediate commit.
- Merge the intermediate commit with A.

With GIT_TEST_COMMIT_GRAPH=1, we write a commit-graph and subsequently
use the corrected committer date, which changes the order in which
commits are merged:
- Merge A with B to form an intermediate commit.
- Merge the intermediate commit with C.

While resulting repositories are equivalent, 6404.4 'virtual trees were
processed' fails with GIT_TEST_COMMIT_GRAPH=1 as we are selecting
different merge-bases and thus have different object ids for the
intermediate commits.

As this has already causes problems (as noted in 859fdc0 (commit-graph:
define GIT_TEST_COMMIT_GRAPH, 2018-08-29)), we disable commit graph
within t6404-recursive-merge.

Signed-off-by: Abhishek Kumar <abhishekkumar8222@gmail.com>
Reviewed-by: Taylor Blau <me@ttaylorr.com>
Reviewed-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-01-18 16:21:18 -08:00

805 lines
20 KiB
C

#include "cache.h"
#include "commit.h"
#include "commit-graph.h"
#include "decorate.h"
#include "prio-queue.h"
#include "tree.h"
#include "ref-filter.h"
#include "revision.h"
#include "tag.h"
#include "commit-reach.h"
/* Remember to update object flag allocation in object.h */
#define PARENT1 (1u<<16)
#define PARENT2 (1u<<17)
#define STALE (1u<<18)
#define RESULT (1u<<19)
static const unsigned all_flags = (PARENT1 | PARENT2 | STALE | RESULT);
static int queue_has_nonstale(struct prio_queue *queue)
{
int i;
for (i = 0; i < queue->nr; i++) {
struct commit *commit = queue->array[i].data;
if (!(commit->object.flags & STALE))
return 1;
}
return 0;
}
/* all input commits in one and twos[] must have been parsed! */
static struct commit_list *paint_down_to_common(struct repository *r,
struct commit *one, int n,
struct commit **twos,
timestamp_t min_generation)
{
struct prio_queue queue = { compare_commits_by_gen_then_commit_date };
struct commit_list *result = NULL;
int i;
timestamp_t last_gen = GENERATION_NUMBER_INFINITY;
if (!min_generation && !corrected_commit_dates_enabled(r))
queue.compare = compare_commits_by_commit_date;
one->object.flags |= PARENT1;
if (!n) {
commit_list_append(one, &result);
return result;
}
prio_queue_put(&queue, one);
for (i = 0; i < n; i++) {
twos[i]->object.flags |= PARENT2;
prio_queue_put(&queue, twos[i]);
}
while (queue_has_nonstale(&queue)) {
struct commit *commit = prio_queue_get(&queue);
struct commit_list *parents;
int flags;
timestamp_t generation = commit_graph_generation(commit);
if (min_generation && generation > last_gen)
BUG("bad generation skip %"PRItime" > %"PRItime" at %s",
generation, last_gen,
oid_to_hex(&commit->object.oid));
last_gen = generation;
if (generation < min_generation)
break;
flags = commit->object.flags & (PARENT1 | PARENT2 | STALE);
if (flags == (PARENT1 | PARENT2)) {
if (!(commit->object.flags & RESULT)) {
commit->object.flags |= RESULT;
commit_list_insert_by_date(commit, &result);
}
/* Mark parents of a found merge stale */
flags |= STALE;
}
parents = commit->parents;
while (parents) {
struct commit *p = parents->item;
parents = parents->next;
if ((p->object.flags & flags) == flags)
continue;
if (repo_parse_commit(r, p))
return NULL;
p->object.flags |= flags;
prio_queue_put(&queue, p);
}
}
clear_prio_queue(&queue);
return result;
}
static struct commit_list *merge_bases_many(struct repository *r,
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 (repo_parse_commit(r, one))
return NULL;
for (i = 0; i < n; i++) {
if (repo_parse_commit(r, twos[i]))
return NULL;
}
list = paint_down_to_common(r, one, n, twos, 0);
while (list) {
struct commit *commit = pop_commit(&list);
if (!(commit->object.flags & STALE))
commit_list_insert_by_date(commit, &result);
}
return result;
}
struct commit_list *get_octopus_merge_bases(struct commit_list *in)
{
struct commit_list *i, *j, *k, *ret = NULL;
if (!in)
return ret;
commit_list_insert(in->item, &ret);
for (i = in->next; i; i = i->next) {
struct commit_list *new_commits = NULL, *end = NULL;
for (j = ret; j; j = j->next) {
struct commit_list *bases;
bases = get_merge_bases(i->item, j->item);
if (!new_commits)
new_commits = bases;
else
end->next = bases;
for (k = bases; k; k = k->next)
end = k;
}
ret = new_commits;
}
return ret;
}
static int remove_redundant(struct repository *r, 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);
ALLOC_ARRAY(filled_index, cnt - 1);
for (i = 0; i < cnt; i++)
repo_parse_commit(r, array[i]);
for (i = 0; i < cnt; i++) {
struct commit_list *common;
timestamp_t min_generation = commit_graph_generation(array[i]);
if (redundant[i])
continue;
for (j = filled = 0; j < cnt; j++) {
timestamp_t curr_generation;
if (i == j || redundant[j])
continue;
filled_index[filled] = j;
work[filled++] = array[j];
curr_generation = commit_graph_generation(array[j]);
if (curr_generation < min_generation)
min_generation = curr_generation;
}
common = paint_down_to_common(r, array[i], filled,
work, min_generation);
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);
clear_commit_marks_many(filled, work, all_flags);
free_commit_list(common);
}
/* Now collect the result */
COPY_ARRAY(work, 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;
}
static struct commit_list *get_merge_bases_many_0(struct repository *r,
struct commit *one,
int n,
struct commit **twos,
int cleanup)
{
struct commit_list *list;
struct commit **rslt;
struct commit_list *result;
int cnt, i;
result = merge_bases_many(r, one, n, twos);
for (i = 0; i < n; i++) {
if (one == twos[i])
return result;
}
if (!result || !result->next) {
if (cleanup) {
clear_commit_marks(one, all_flags);
clear_commit_marks_many(n, twos, all_flags);
}
return result;
}
/* There are more than one */
cnt = commit_list_count(result);
rslt = xcalloc(cnt, sizeof(*rslt));
for (list = result, i = 0; list; list = list->next)
rslt[i++] = list->item;
free_commit_list(result);
clear_commit_marks(one, all_flags);
clear_commit_marks_many(n, twos, all_flags);
cnt = remove_redundant(r, rslt, cnt);
result = NULL;
for (i = 0; i < cnt; i++)
commit_list_insert_by_date(rslt[i], &result);
free(rslt);
return result;
}
struct commit_list *repo_get_merge_bases_many(struct repository *r,
struct commit *one,
int n,
struct commit **twos)
{
return get_merge_bases_many_0(r, one, n, twos, 1);
}
struct commit_list *repo_get_merge_bases_many_dirty(struct repository *r,
struct commit *one,
int n,
struct commit **twos)
{
return get_merge_bases_many_0(r, one, n, twos, 0);
}
struct commit_list *repo_get_merge_bases(struct repository *r,
struct commit *one,
struct commit *two)
{
return get_merge_bases_many_0(r, one, 1, &two, 1);
}
/*
* Is "commit" a descendant of one of the elements on the "with_commit" list?
*/
int repo_is_descendant_of(struct repository *r,
struct commit *commit,
struct commit_list *with_commit)
{
if (!with_commit)
return 1;
if (generation_numbers_enabled(the_repository)) {
struct commit_list *from_list = NULL;
int result;
commit_list_insert(commit, &from_list);
result = can_all_from_reach(from_list, with_commit, 0);
free_commit_list(from_list);
return result;
} else {
while (with_commit) {
struct commit *other;
other = with_commit->item;
with_commit = with_commit->next;
if (repo_in_merge_bases_many(r, other, 1, &commit))
return 1;
}
return 0;
}
}
/*
* Is "commit" an ancestor of one of the "references"?
*/
int repo_in_merge_bases_many(struct repository *r, struct commit *commit,
int nr_reference, struct commit **reference)
{
struct commit_list *bases;
int ret = 0, i;
timestamp_t generation, max_generation = GENERATION_NUMBER_ZERO;
if (repo_parse_commit(r, commit))
return ret;
for (i = 0; i < nr_reference; i++) {
if (repo_parse_commit(r, reference[i]))
return ret;
generation = commit_graph_generation(reference[i]);
if (generation > max_generation)
max_generation = generation;
}
generation = commit_graph_generation(commit);
if (generation > max_generation)
return ret;
bases = paint_down_to_common(r, commit,
nr_reference, reference,
generation);
if (commit->object.flags & PARENT2)
ret = 1;
clear_commit_marks(commit, all_flags);
clear_commit_marks_many(nr_reference, reference, all_flags);
free_commit_list(bases);
return ret;
}
/*
* Is "commit" an ancestor of (i.e. reachable from) the "reference"?
*/
int repo_in_merge_bases(struct repository *r,
struct commit *commit,
struct commit *reference)
{
int res;
struct commit_list *list = NULL;
struct commit_list **next = &list;
next = commit_list_append(commit, next);
res = repo_is_descendant_of(r, reference, list);
free_commit_list(list);
return res;
}
struct commit_list *reduce_heads(struct commit_list *heads)
{
struct commit_list *p;
struct commit_list *result = NULL, **tail = &result;
struct commit **array;
int num_head, i;
if (!heads)
return NULL;
/* 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;
p->item->object.flags |= STALE;
num_head++;
}
array = xcalloc(num_head, sizeof(*array));
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(the_repository, array, num_head);
for (i = 0; i < num_head; i++)
tail = &commit_list_insert(array[i], tail)->next;
free(array);
return result;
}
void reduce_heads_replace(struct commit_list **heads)
{
struct commit_list *result = reduce_heads(*heads);
free_commit_list(*heads);
*heads = result;
}
int ref_newer(const struct object_id *new_oid, const struct object_id *old_oid)
{
struct object *o;
struct commit *old_commit, *new_commit;
struct commit_list *old_commit_list = NULL;
int ret;
/*
* Both new_commit and old_commit must be commit-ish and new_commit is descendant of
* old_commit. Otherwise we require --force.
*/
o = deref_tag(the_repository, parse_object(the_repository, old_oid),
NULL, 0);
if (!o || o->type != OBJ_COMMIT)
return 0;
old_commit = (struct commit *) o;
o = deref_tag(the_repository, parse_object(the_repository, new_oid),
NULL, 0);
if (!o || o->type != OBJ_COMMIT)
return 0;
new_commit = (struct commit *) o;
if (parse_commit(new_commit) < 0)
return 0;
commit_list_insert(old_commit, &old_commit_list);
ret = repo_is_descendant_of(the_repository,
new_commit, old_commit_list);
free_commit_list(old_commit_list);
return ret;
}
/*
* Mimicking the real stack, this stack lives on the heap, avoiding stack
* overflows.
*
* At each recursion step, the stack items points to the commits whose
* ancestors are to be inspected.
*/
struct contains_stack {
int nr, alloc;
struct contains_stack_entry {
struct commit *commit;
struct commit_list *parents;
} *contains_stack;
};
static int in_commit_list(const struct commit_list *want, struct commit *c)
{
for (; want; want = want->next)
if (oideq(&want->item->object.oid, &c->object.oid))
return 1;
return 0;
}
/*
* Test whether the candidate is contained in the list.
* Do not recurse to find out, though, but return -1 if inconclusive.
*/
static enum contains_result contains_test(struct commit *candidate,
const struct commit_list *want,
struct contains_cache *cache,
timestamp_t cutoff)
{
enum contains_result *cached = contains_cache_at(cache, candidate);
/* If we already have the answer cached, return that. */
if (*cached)
return *cached;
/* or are we it? */
if (in_commit_list(want, candidate)) {
*cached = CONTAINS_YES;
return CONTAINS_YES;
}
/* Otherwise, we don't know; prepare to recurse */
parse_commit_or_die(candidate);
if (commit_graph_generation(candidate) < cutoff)
return CONTAINS_NO;
return CONTAINS_UNKNOWN;
}
static void push_to_contains_stack(struct commit *candidate, struct contains_stack *contains_stack)
{
ALLOC_GROW(contains_stack->contains_stack, contains_stack->nr + 1, contains_stack->alloc);
contains_stack->contains_stack[contains_stack->nr].commit = candidate;
contains_stack->contains_stack[contains_stack->nr++].parents = candidate->parents;
}
static enum contains_result contains_tag_algo(struct commit *candidate,
const struct commit_list *want,
struct contains_cache *cache)
{
struct contains_stack contains_stack = { 0, 0, NULL };
enum contains_result result;
timestamp_t cutoff = GENERATION_NUMBER_INFINITY;
const struct commit_list *p;
for (p = want; p; p = p->next) {
timestamp_t generation;
struct commit *c = p->item;
load_commit_graph_info(the_repository, c);
generation = commit_graph_generation(c);
if (generation < cutoff)
cutoff = generation;
}
result = contains_test(candidate, want, cache, cutoff);
if (result != CONTAINS_UNKNOWN)
return result;
push_to_contains_stack(candidate, &contains_stack);
while (contains_stack.nr) {
struct contains_stack_entry *entry = &contains_stack.contains_stack[contains_stack.nr - 1];
struct commit *commit = entry->commit;
struct commit_list *parents = entry->parents;
if (!parents) {
*contains_cache_at(cache, commit) = CONTAINS_NO;
contains_stack.nr--;
}
/*
* If we just popped the stack, parents->item has been marked,
* therefore contains_test will return a meaningful yes/no.
*/
else switch (contains_test(parents->item, want, cache, cutoff)) {
case CONTAINS_YES:
*contains_cache_at(cache, commit) = CONTAINS_YES;
contains_stack.nr--;
break;
case CONTAINS_NO:
entry->parents = parents->next;
break;
case CONTAINS_UNKNOWN:
push_to_contains_stack(parents->item, &contains_stack);
break;
}
}
free(contains_stack.contains_stack);
return contains_test(candidate, want, cache, cutoff);
}
int commit_contains(struct ref_filter *filter, struct commit *commit,
struct commit_list *list, struct contains_cache *cache)
{
if (filter->with_commit_tag_algo)
return contains_tag_algo(commit, list, cache) == CONTAINS_YES;
return repo_is_descendant_of(the_repository, commit, list);
}
static int compare_commits_by_gen(const void *_a, const void *_b)
{
const struct commit *a = *(const struct commit * const *)_a;
const struct commit *b = *(const struct commit * const *)_b;
timestamp_t generation_a = commit_graph_generation(a);
timestamp_t generation_b = commit_graph_generation(b);
if (generation_a < generation_b)
return -1;
if (generation_a > generation_b)
return 1;
return 0;
}
int can_all_from_reach_with_flag(struct object_array *from,
unsigned int with_flag,
unsigned int assign_flag,
time_t min_commit_date,
timestamp_t min_generation)
{
struct commit **list = NULL;
int i;
int nr_commits;
int result = 1;
ALLOC_ARRAY(list, from->nr);
nr_commits = 0;
for (i = 0; i < from->nr; i++) {
struct object *from_one = from->objects[i].item;
if (!from_one || from_one->flags & assign_flag)
continue;
from_one = deref_tag(the_repository, from_one,
"a from object", 0);
if (!from_one || from_one->type != OBJ_COMMIT) {
/*
* no way to tell if this is reachable by
* looking at the ancestry chain alone, so
* leave a note to ourselves not to worry about
* this object anymore.
*/
from->objects[i].item->flags |= assign_flag;
continue;
}
list[nr_commits] = (struct commit *)from_one;
if (parse_commit(list[nr_commits]) ||
commit_graph_generation(list[nr_commits]) < min_generation) {
result = 0;
goto cleanup;
}
nr_commits++;
}
QSORT(list, nr_commits, compare_commits_by_gen);
for (i = 0; i < nr_commits; i++) {
/* DFS from list[i] */
struct commit_list *stack = NULL;
list[i]->object.flags |= assign_flag;
commit_list_insert(list[i], &stack);
while (stack) {
struct commit_list *parent;
if (stack->item->object.flags & (with_flag | RESULT)) {
pop_commit(&stack);
if (stack)
stack->item->object.flags |= RESULT;
continue;
}
for (parent = stack->item->parents; parent; parent = parent->next) {
if (parent->item->object.flags & (with_flag | RESULT))
stack->item->object.flags |= RESULT;
if (!(parent->item->object.flags & assign_flag)) {
parent->item->object.flags |= assign_flag;
if (parse_commit(parent->item) ||
parent->item->date < min_commit_date ||
commit_graph_generation(parent->item) < min_generation)
continue;
commit_list_insert(parent->item, &stack);
break;
}
}
if (!parent)
pop_commit(&stack);
}
if (!(list[i]->object.flags & (with_flag | RESULT))) {
result = 0;
goto cleanup;
}
}
cleanup:
clear_commit_marks_many(nr_commits, list, RESULT | assign_flag);
free(list);
for (i = 0; i < from->nr; i++)
from->objects[i].item->flags &= ~assign_flag;
return result;
}
int can_all_from_reach(struct commit_list *from, struct commit_list *to,
int cutoff_by_min_date)
{
struct object_array from_objs = OBJECT_ARRAY_INIT;
time_t min_commit_date = cutoff_by_min_date ? from->item->date : 0;
struct commit_list *from_iter = from, *to_iter = to;
int result;
timestamp_t min_generation = GENERATION_NUMBER_INFINITY;
while (from_iter) {
add_object_array(&from_iter->item->object, NULL, &from_objs);
if (!parse_commit(from_iter->item)) {
timestamp_t generation;
if (from_iter->item->date < min_commit_date)
min_commit_date = from_iter->item->date;
generation = commit_graph_generation(from_iter->item);
if (generation < min_generation)
min_generation = generation;
}
from_iter = from_iter->next;
}
while (to_iter) {
if (!parse_commit(to_iter->item)) {
timestamp_t generation;
if (to_iter->item->date < min_commit_date)
min_commit_date = to_iter->item->date;
generation = commit_graph_generation(to_iter->item);
if (generation < min_generation)
min_generation = generation;
}
to_iter->item->object.flags |= PARENT2;
to_iter = to_iter->next;
}
result = can_all_from_reach_with_flag(&from_objs, PARENT2, PARENT1,
min_commit_date, min_generation);
while (from) {
clear_commit_marks(from->item, PARENT1);
from = from->next;
}
while (to) {
clear_commit_marks(to->item, PARENT2);
to = to->next;
}
object_array_clear(&from_objs);
return result;
}
struct commit_list *get_reachable_subset(struct commit **from, int nr_from,
struct commit **to, int nr_to,
unsigned int reachable_flag)
{
struct commit **item;
struct commit *current;
struct commit_list *found_commits = NULL;
struct commit **to_last = to + nr_to;
struct commit **from_last = from + nr_from;
timestamp_t min_generation = GENERATION_NUMBER_INFINITY;
int num_to_find = 0;
struct prio_queue queue = { compare_commits_by_gen_then_commit_date };
for (item = to; item < to_last; item++) {
timestamp_t generation;
struct commit *c = *item;
parse_commit(c);
generation = commit_graph_generation(c);
if (generation < min_generation)
min_generation = generation;
if (!(c->object.flags & PARENT1)) {
c->object.flags |= PARENT1;
num_to_find++;
}
}
for (item = from; item < from_last; item++) {
struct commit *c = *item;
if (!(c->object.flags & PARENT2)) {
c->object.flags |= PARENT2;
parse_commit(c);
prio_queue_put(&queue, *item);
}
}
while (num_to_find && (current = prio_queue_get(&queue)) != NULL) {
struct commit_list *parents;
if (current->object.flags & PARENT1) {
current->object.flags &= ~PARENT1;
current->object.flags |= reachable_flag;
commit_list_insert(current, &found_commits);
num_to_find--;
}
for (parents = current->parents; parents; parents = parents->next) {
struct commit *p = parents->item;
parse_commit(p);
if (commit_graph_generation(p) < min_generation)
continue;
if (p->object.flags & PARENT2)
continue;
p->object.flags |= PARENT2;
prio_queue_put(&queue, p);
}
}
clear_commit_marks_many(nr_to, to, PARENT1);
clear_commit_marks_many(nr_from, from, PARENT2);
return found_commits;
}