--- /dev/null
- if (!peel_iterated_oid(oid, &peeled))
+ #include "git-compat-util.h"
+ #include "pseudo-merge.h"
+ #include "date.h"
+ #include "oid-array.h"
+ #include "strbuf.h"
+ #include "config.h"
+ #include "string-list.h"
+ #include "refs.h"
+ #include "pack-bitmap.h"
+ #include "commit.h"
+ #include "alloc.h"
+ #include "progress.h"
+ #include "hex.h"
+
+ #define DEFAULT_PSEUDO_MERGE_DECAY 1.0
+ #define DEFAULT_PSEUDO_MERGE_MAX_MERGES 64
+ #define DEFAULT_PSEUDO_MERGE_SAMPLE_RATE 1
+ #define DEFAULT_PSEUDO_MERGE_THRESHOLD approxidate("1.week.ago")
+ #define DEFAULT_PSEUDO_MERGE_STABLE_THRESHOLD approxidate("1.month.ago")
+ #define DEFAULT_PSEUDO_MERGE_STABLE_SIZE 512
+
+ static double gitexp(double base, int exp)
+ {
+ double result = 1;
+ while (1) {
+ if (exp % 2)
+ result *= base;
+ exp >>= 1;
+ if (!exp)
+ break;
+ base *= base;
+ }
+ return result;
+ }
+
+ static uint32_t pseudo_merge_group_size(const struct pseudo_merge_group *group,
+ const struct pseudo_merge_matches *matches,
+ uint32_t i)
+ {
+ double C = 0.0f;
+ uint32_t n;
+
+ /*
+ * The size of pseudo-merge groups decays according to a power series,
+ * which looks like:
+ *
+ * f(n) = C * n^-k
+ *
+ * , where 'n' is the n-th pseudo-merge group, 'f(n)' is its size, 'k'
+ * is the decay rate, and 'C' is a scaling value.
+ *
+ * The value of C depends on the number of groups, decay rate, and total
+ * number of commits. It is computed such that if there are M and N
+ * total groups and commits, respectively, that:
+ *
+ * N = f(0) + f(1) + ... f(M-1)
+ *
+ * Rearranging to isolate C, we get:
+ *
+ * N = \sum_{n=1}^M C / n^k
+ *
+ * N / C = \sum_{n=1}^M n^-k
+ *
+ * C = N / \sum_{n=1}^M n^-k
+ *
+ * For example, if we have a decay rate of 'k' being equal to 1.5, 'N'
+ * total commits equal to 10,000, and 'M' being equal to 6 groups, then
+ * the (rounded) group sizes are:
+ *
+ * { 5469, 1934, 1053, 684, 489, 372 }
+ *
+ * increasing the number of total groups, say to 10, scales the group
+ * sizes appropriately:
+ *
+ * { 5012, 1772, 964, 626, 448, 341, 271, 221, 186, 158 }
+ */
+ for (n = 0; n < group->max_merges; n++)
+ C += 1.0 / gitexp(n + 1, group->decay);
+ C = matches->unstable_nr / C;
+
+ return (uint32_t)((C / gitexp(i + 1, group->decay)) + 0.5);
+ }
+
+ static void pseudo_merge_group_init(struct pseudo_merge_group *group)
+ {
+ memset(group, 0, sizeof(struct pseudo_merge_group));
+
+ strmap_init_with_options(&group->matches, NULL, 0);
+
+ group->decay = DEFAULT_PSEUDO_MERGE_DECAY;
+ group->max_merges = DEFAULT_PSEUDO_MERGE_MAX_MERGES;
+ group->sample_rate = DEFAULT_PSEUDO_MERGE_SAMPLE_RATE;
+ group->threshold = DEFAULT_PSEUDO_MERGE_THRESHOLD;
+ group->stable_threshold = DEFAULT_PSEUDO_MERGE_STABLE_THRESHOLD;
+ group->stable_size = DEFAULT_PSEUDO_MERGE_STABLE_SIZE;
+ }
+
+ static int pseudo_merge_config(const char *var, const char *value,
+ const struct config_context *ctx,
+ void *cb_data)
+ {
+ struct string_list *list = cb_data;
+ struct string_list_item *item;
+ struct pseudo_merge_group *group;
+ struct strbuf buf = STRBUF_INIT;
+ const char *sub, *key;
+ size_t sub_len;
+ int ret = 0;
+
+ if (parse_config_key(var, "bitmappseudomerge", &sub, &sub_len, &key))
+ goto done;
+
+ if (!sub_len)
+ goto done;
+
+ strbuf_add(&buf, sub, sub_len);
+
+ item = string_list_lookup(list, buf.buf);
+ if (!item) {
+ item = string_list_insert(list, buf.buf);
+
+ item->util = xmalloc(sizeof(struct pseudo_merge_group));
+ pseudo_merge_group_init(item->util);
+ }
+
+ group = item->util;
+
+ if (!strcmp(key, "pattern")) {
+ struct strbuf re = STRBUF_INIT;
+
+ free(group->pattern);
+ if (*value != '^')
+ strbuf_addch(&re, '^');
+ strbuf_addstr(&re, value);
+
+ group->pattern = xcalloc(1, sizeof(regex_t));
+ if (regcomp(group->pattern, re.buf, REG_EXTENDED))
+ die(_("failed to load pseudo-merge regex for %s: '%s'"),
+ sub, re.buf);
+
+ strbuf_release(&re);
+ } else if (!strcmp(key, "decay")) {
+ group->decay = git_config_double(var, value, ctx->kvi);
+ if (group->decay < 0) {
+ warning(_("%s must be non-negative, using default"), var);
+ group->decay = DEFAULT_PSEUDO_MERGE_DECAY;
+ }
+ } else if (!strcmp(key, "samplerate")) {
+ group->sample_rate = git_config_double(var, value, ctx->kvi);
+ if (!(0 <= group->sample_rate && group->sample_rate <= 1)) {
+ warning(_("%s must be between 0 and 1, using default"), var);
+ group->sample_rate = DEFAULT_PSEUDO_MERGE_SAMPLE_RATE;
+ }
+ } else if (!strcmp(key, "threshold")) {
+ if (git_config_expiry_date(&group->threshold, var, value)) {
+ ret = -1;
+ goto done;
+ }
+ } else if (!strcmp(key, "maxmerges")) {
+ group->max_merges = git_config_int(var, value, ctx->kvi);
+ if (group->max_merges < 0) {
+ warning(_("%s must be non-negative, using default"), var);
+ group->max_merges = DEFAULT_PSEUDO_MERGE_MAX_MERGES;
+ }
+ } else if (!strcmp(key, "stablethreshold")) {
+ if (git_config_expiry_date(&group->stable_threshold, var, value)) {
+ ret = -1;
+ goto done;
+ }
+ } else if (!strcmp(key, "stablesize")) {
+ group->stable_size = git_config_int(var, value, ctx->kvi);
+ if (group->stable_size <= 0) {
+ warning(_("%s must be positive, using default"), var);
+ group->stable_size = DEFAULT_PSEUDO_MERGE_STABLE_SIZE;
+ }
+ }
+
+ done:
+ strbuf_release(&buf);
+
+ return ret;
+ }
+
+ void load_pseudo_merges_from_config(struct string_list *list)
+ {
+ struct string_list_item *item;
+
+ git_config(pseudo_merge_config, list);
+
+ for_each_string_list_item(item, list) {
+ struct pseudo_merge_group *group = item->util;
+ if (!group->pattern)
+ die(_("pseudo-merge group '%s' missing required pattern"),
+ item->string);
+ if (group->threshold < group->stable_threshold)
+ die(_("pseudo-merge group '%s' has unstable threshold "
+ "before stable one"), item->string);
+ }
+ }
+
+ static int find_pseudo_merge_group_for_ref(const char *refname,
+ const struct object_id *oid,
+ int flags UNUSED,
+ void *_data)
+ {
+ struct bitmap_writer *writer = _data;
+ struct object_id peeled;
+ struct commit *c;
+ uint32_t i;
+ int has_bitmap;
+
- for_each_ref(find_pseudo_merge_group_for_ref, writer);
++ if (!peel_iterated_oid(the_repository, oid, &peeled))
+ oid = &peeled;
+
+ c = lookup_commit(the_repository, oid);
+ if (!c)
+ return 0;
+
+ has_bitmap = bitmap_writer_has_bitmapped_object_id(writer, oid);
+
+ for (i = 0; i < writer->pseudo_merge_groups.nr; i++) {
+ struct pseudo_merge_group *group;
+ struct pseudo_merge_matches *matches;
+ struct strbuf group_name = STRBUF_INIT;
+ regmatch_t captures[16];
+ size_t j;
+
+ group = writer->pseudo_merge_groups.items[i].util;
+ if (regexec(group->pattern, refname, ARRAY_SIZE(captures),
+ captures, 0))
+ continue;
+
+ if (captures[ARRAY_SIZE(captures) - 1].rm_so != -1)
+ warning(_("pseudo-merge regex from config has too many capture "
+ "groups (max=%"PRIuMAX")"),
+ (uintmax_t)ARRAY_SIZE(captures) - 2);
+
+ for (j = !!group->pattern->re_nsub; j < ARRAY_SIZE(captures); j++) {
+ regmatch_t *match = &captures[j];
+ if (match->rm_so == -1)
+ continue;
+
+ if (group_name.len)
+ strbuf_addch(&group_name, '-');
+
+ strbuf_add(&group_name, refname + match->rm_so,
+ match->rm_eo - match->rm_so);
+ }
+
+ matches = strmap_get(&group->matches, group_name.buf);
+ if (!matches) {
+ matches = xcalloc(1, sizeof(*matches));
+ strmap_put(&group->matches, strbuf_detach(&group_name, NULL),
+ matches);
+ }
+
+ if (c->date <= group->stable_threshold) {
+ ALLOC_GROW(matches->stable, matches->stable_nr + 1,
+ matches->stable_alloc);
+ matches->stable[matches->stable_nr++] = c;
+ } else if (c->date <= group->threshold && !has_bitmap) {
+ ALLOC_GROW(matches->unstable, matches->unstable_nr + 1,
+ matches->unstable_alloc);
+ matches->unstable[matches->unstable_nr++] = c;
+ }
+
+ strbuf_release(&group_name);
+ }
+
+ return 0;
+ }
+
+ static struct commit *push_pseudo_merge(struct pseudo_merge_group *group)
+ {
+ struct commit *merge;
+
+ ALLOC_GROW(group->merges, group->merges_nr + 1, group->merges_alloc);
+
+ merge = alloc_commit_node(the_repository);
+ merge->object.parsed = 1;
+ merge->object.flags |= BITMAP_PSEUDO_MERGE;
+
+ group->merges[group->merges_nr++] = merge;
+
+ return merge;
+ }
+
+ static struct pseudo_merge_commit_idx *pseudo_merge_idx(kh_oid_map_t *pseudo_merge_commits,
+ const struct object_id *oid)
+
+ {
+ struct pseudo_merge_commit_idx *pmc;
+ int hash_ret;
+ khiter_t hash_pos = kh_put_oid_map(pseudo_merge_commits, *oid,
+ &hash_ret);
+
+ if (hash_ret) {
+ CALLOC_ARRAY(pmc, 1);
+ kh_value(pseudo_merge_commits, hash_pos) = pmc;
+ } else {
+ pmc = kh_value(pseudo_merge_commits, hash_pos);
+ }
+
+ return pmc;
+ }
+
+ #define MIN_PSEUDO_MERGE_SIZE 8
+
+ static void select_pseudo_merges_1(struct bitmap_writer *writer,
+ struct pseudo_merge_group *group,
+ struct pseudo_merge_matches *matches)
+ {
+ uint32_t i, j;
+ uint32_t stable_merges_nr;
+
+ if (!matches->stable_nr && !matches->unstable_nr)
+ return; /* all tips in this group already have bitmaps */
+
+ stable_merges_nr = matches->stable_nr / group->stable_size;
+ if (matches->stable_nr % group->stable_size)
+ stable_merges_nr++;
+
+ /* make stable_merges_nr pseudo merges for stable commits */
+ for (i = 0, j = 0; i < stable_merges_nr; i++) {
+ struct commit *merge;
+ struct commit_list **p;
+
+ merge = push_pseudo_merge(group);
+ p = &merge->parents;
+
+ /*
+ * For each pseudo-merge created above, add parents to the
+ * allocated commit node from the stable set of commits
+ * (un-bitmapped, newer than the stable threshold).
+ */
+ do {
+ struct commit *c;
+ struct pseudo_merge_commit_idx *pmc;
+
+ if (j >= matches->stable_nr)
+ break;
+
+ c = matches->stable[j++];
+ /*
+ * Here and below, make sure that we keep our mapping of
+ * commits -> pseudo-merge(s) which include the key'd
+ * commit up-to-date.
+ */
+ pmc = pseudo_merge_idx(writer->pseudo_merge_commits,
+ &c->object.oid);
+
+ ALLOC_GROW(pmc->pseudo_merge, pmc->nr + 1, pmc->alloc);
+
+ pmc->pseudo_merge[pmc->nr++] = writer->pseudo_merges_nr;
+ p = commit_list_append(c, p);
+ } while (j % group->stable_size);
+
+ bitmap_writer_push_commit(writer, merge, 1);
+ writer->pseudo_merges_nr++;
+ }
+
+ /* make up to group->max_merges pseudo merges for unstable commits */
+ for (i = 0, j = 0; i < group->max_merges; i++) {
+ struct commit *merge;
+ struct commit_list **p;
+ uint32_t size, end;
+
+ merge = push_pseudo_merge(group);
+ p = &merge->parents;
+
+ size = pseudo_merge_group_size(group, matches, i);
+ end = size < MIN_PSEUDO_MERGE_SIZE ? matches->unstable_nr : j + size;
+
+ /*
+ * For each pseudo-merge commit created above, add parents to
+ * the allocated commit node from the unstable set of commits
+ * (newer than the stable threshold).
+ *
+ * Account for the sample rate, since not every candidate from
+ * the set of stable commits will be included as a pseudo-merge
+ * parent.
+ */
+ for (; j < end && j < matches->unstable_nr; j++) {
+ struct commit *c = matches->unstable[j];
+ struct pseudo_merge_commit_idx *pmc;
+
+ if (j % (uint32_t)(1.0 / group->sample_rate))
+ continue;
+
+ pmc = pseudo_merge_idx(writer->pseudo_merge_commits,
+ &c->object.oid);
+
+ ALLOC_GROW(pmc->pseudo_merge, pmc->nr + 1, pmc->alloc);
+
+ pmc->pseudo_merge[pmc->nr++] = writer->pseudo_merges_nr;
+ p = commit_list_append(c, p);
+ }
+
+ bitmap_writer_push_commit(writer, merge, 1);
+ writer->pseudo_merges_nr++;
+ if (end >= matches->unstable_nr)
+ break;
+ }
+ }
+
+ static int commit_date_cmp(const void *va, const void *vb)
+ {
+ timestamp_t a = (*(const struct commit **)va)->date;
+ timestamp_t b = (*(const struct commit **)vb)->date;
+
+ if (a < b)
+ return -1;
+ else if (a > b)
+ return 1;
+ return 0;
+ }
+
+ static void sort_pseudo_merge_matches(struct pseudo_merge_matches *matches)
+ {
+ QSORT(matches->stable, matches->stable_nr, commit_date_cmp);
+ QSORT(matches->unstable, matches->unstable_nr, commit_date_cmp);
+ }
+
+ void select_pseudo_merges(struct bitmap_writer *writer,
+ struct commit **commits, size_t commits_nr)
+ {
+ struct progress *progress = NULL;
+ uint32_t i;
+
+ if (!writer->pseudo_merge_groups.nr)
+ return;
+
+ if (writer->show_progress)
+ progress = start_progress("Selecting pseudo-merge commits",
+ writer->pseudo_merge_groups.nr);
+
++ refs_for_each_ref(get_main_ref_store(the_repository),
++ find_pseudo_merge_group_for_ref, writer);
+
+ for (i = 0; i < writer->pseudo_merge_groups.nr; i++) {
+ struct pseudo_merge_group *group;
+ struct hashmap_iter iter;
+ struct strmap_entry *e;
+
+ group = writer->pseudo_merge_groups.items[i].util;
+ strmap_for_each_entry(&group->matches, &iter, e) {
+ struct pseudo_merge_matches *matches = e->value;
+
+ sort_pseudo_merge_matches(matches);
+
+ select_pseudo_merges_1(writer, group, matches);
+ }
+
+ display_progress(progress, i + 1);
+ }
+
+ stop_progress(&progress);
+ }
+
+ void free_pseudo_merge_map(struct pseudo_merge_map *pm)
+ {
+ uint32_t i;
+ for (i = 0; i < pm->nr; i++) {
+ ewah_pool_free(pm->v[i].commits);
+ ewah_pool_free(pm->v[i].bitmap);
+ }
+ free(pm->v);
+ }
+
+ struct pseudo_merge_commit_ext {
+ uint32_t nr;
+ const unsigned char *ptr;
+ };
+
+ static int pseudo_merge_ext_at(const struct pseudo_merge_map *pm,
+ struct pseudo_merge_commit_ext *ext, size_t at)
+ {
+ if (at >= pm->map_size)
+ return error(_("extended pseudo-merge read out-of-bounds "
+ "(%"PRIuMAX" >= %"PRIuMAX")"),
+ (uintmax_t)at, (uintmax_t)pm->map_size);
+ if (at + 4 >= pm->map_size)
+ return error(_("extended pseudo-merge entry is too short "
+ "(%"PRIuMAX" >= %"PRIuMAX")"),
+ (uintmax_t)(at + 4), (uintmax_t)pm->map_size);
+
+ ext->nr = get_be32(pm->map + at);
+ ext->ptr = pm->map + at + sizeof(uint32_t);
+
+ return 0;
+ }
+
+ struct ewah_bitmap *pseudo_merge_bitmap(const struct pseudo_merge_map *pm,
+ struct pseudo_merge *merge)
+ {
+ if (!merge->loaded_commits)
+ BUG("cannot use unloaded pseudo-merge bitmap");
+
+ if (!merge->loaded_bitmap) {
+ size_t at = merge->bitmap_at;
+
+ merge->bitmap = read_bitmap(pm->map, pm->map_size, &at);
+ merge->loaded_bitmap = 1;
+ }
+
+ return merge->bitmap;
+ }
+
+ struct pseudo_merge *use_pseudo_merge(const struct pseudo_merge_map *pm,
+ struct pseudo_merge *merge)
+ {
+ if (!merge->loaded_commits) {
+ size_t pos = merge->at;
+
+ merge->commits = read_bitmap(pm->map, pm->map_size, &pos);
+ merge->bitmap_at = pos;
+ merge->loaded_commits = 1;
+ }
+ return merge;
+ }
+
+ static struct pseudo_merge *pseudo_merge_at(const struct pseudo_merge_map *pm,
+ struct object_id *oid,
+ size_t want)
+ {
+ size_t lo = 0;
+ size_t hi = pm->nr;
+
+ while (lo < hi) {
+ size_t mi = lo + (hi - lo) / 2;
+ size_t got = pm->v[mi].at;
+
+ if (got == want)
+ return use_pseudo_merge(pm, &pm->v[mi]);
+ else if (got < want)
+ hi = mi;
+ else
+ lo = mi + 1;
+ }
+
+ warning(_("could not find pseudo-merge for commit %s at offset %"PRIuMAX),
+ oid_to_hex(oid), (uintmax_t)want);
+
+ return NULL;
+ }
+
+ struct pseudo_merge_commit {
+ uint32_t commit_pos;
+ uint64_t pseudo_merge_ofs;
+ };
+
+ #define PSEUDO_MERGE_COMMIT_RAWSZ (sizeof(uint32_t)+sizeof(uint64_t))
+
+ static void read_pseudo_merge_commit_at(struct pseudo_merge_commit *merge,
+ const unsigned char *at)
+ {
+ merge->commit_pos = get_be32(at);
+ merge->pseudo_merge_ofs = get_be64(at + sizeof(uint32_t));
+ }
+
+ static int nth_pseudo_merge_ext(const struct pseudo_merge_map *pm,
+ struct pseudo_merge_commit_ext *ext,
+ struct pseudo_merge_commit *merge,
+ uint32_t n)
+ {
+ size_t ofs;
+
+ if (n >= ext->nr)
+ return error(_("extended pseudo-merge lookup out-of-bounds "
+ "(%"PRIu32" >= %"PRIu32")"), n, ext->nr);
+
+ ofs = get_be64(ext->ptr + st_mult(n, sizeof(uint64_t)));
+ if (ofs >= pm->map_size)
+ return error(_("out-of-bounds read: (%"PRIuMAX" >= %"PRIuMAX")"),
+ (uintmax_t)ofs, (uintmax_t)pm->map_size);
+
+ read_pseudo_merge_commit_at(merge, pm->map + ofs);
+
+ return 0;
+ }
+
+ static unsigned apply_pseudo_merge(const struct pseudo_merge_map *pm,
+ struct pseudo_merge *merge,
+ struct bitmap *result,
+ struct bitmap *roots)
+ {
+ if (merge->satisfied)
+ return 0;
+
+ if (!ewah_bitmap_is_subset(merge->commits, roots ? roots : result))
+ return 0;
+
+ bitmap_or_ewah(result, pseudo_merge_bitmap(pm, merge));
+ if (roots)
+ bitmap_or_ewah(roots, pseudo_merge_bitmap(pm, merge));
+ merge->satisfied = 1;
+
+ return 1;
+ }
+
+ static int pseudo_merge_commit_cmp(const void *va, const void *vb)
+ {
+ struct pseudo_merge_commit merge;
+ uint32_t key = *(uint32_t*)va;
+
+ read_pseudo_merge_commit_at(&merge, vb);
+
+ if (key < merge.commit_pos)
+ return -1;
+ if (key > merge.commit_pos)
+ return 1;
+ return 0;
+ }
+
+ static struct pseudo_merge_commit *find_pseudo_merge(const struct pseudo_merge_map *pm,
+ uint32_t pos)
+ {
+ if (!pm->commits_nr)
+ return NULL;
+
+ return bsearch(&pos, pm->commits, pm->commits_nr,
+ PSEUDO_MERGE_COMMIT_RAWSZ, pseudo_merge_commit_cmp);
+ }
+
+ int apply_pseudo_merges_for_commit(const struct pseudo_merge_map *pm,
+ struct bitmap *result,
+ struct commit *commit, uint32_t commit_pos)
+ {
+ struct pseudo_merge *merge;
+ struct pseudo_merge_commit *merge_commit;
+ int ret = 0;
+
+ merge_commit = find_pseudo_merge(pm, commit_pos);
+ if (!merge_commit)
+ return 0;
+
+ if (merge_commit->pseudo_merge_ofs & ((uint64_t)1<<63)) {
+ struct pseudo_merge_commit_ext ext = { 0 };
+ off_t ofs = merge_commit->pseudo_merge_ofs & ~((uint64_t)1<<63);
+ uint32_t i;
+
+ if (pseudo_merge_ext_at(pm, &ext, ofs) < -1) {
+ warning(_("could not read extended pseudo-merge table "
+ "for commit %s"),
+ oid_to_hex(&commit->object.oid));
+ return ret;
+ }
+
+ for (i = 0; i < ext.nr; i++) {
+ if (nth_pseudo_merge_ext(pm, &ext, merge_commit, i) < 0)
+ return ret;
+
+ merge = pseudo_merge_at(pm, &commit->object.oid,
+ merge_commit->pseudo_merge_ofs);
+
+ if (!merge)
+ return ret;
+
+ if (apply_pseudo_merge(pm, merge, result, NULL))
+ ret++;
+ }
+ } else {
+ merge = pseudo_merge_at(pm, &commit->object.oid,
+ merge_commit->pseudo_merge_ofs);
+
+ if (!merge)
+ return ret;
+
+ if (apply_pseudo_merge(pm, merge, result, NULL))
+ ret++;
+ }
+
+ if (ret)
+ cascade_pseudo_merges(pm, result, NULL);
+
+ return ret;
+ }
+
+ int cascade_pseudo_merges(const struct pseudo_merge_map *pm,
+ struct bitmap *result,
+ struct bitmap *roots)
+ {
+ unsigned any_satisfied;
+ int ret = 0;
+
+ do {
+ struct pseudo_merge *merge;
+ uint32_t i;
+
+ any_satisfied = 0;
+
+ for (i = 0; i < pm->nr; i++) {
+ merge = use_pseudo_merge(pm, &pm->v[i]);
+ if (apply_pseudo_merge(pm, merge, result, roots)) {
+ any_satisfied |= 1;
+ ret++;
+ }
+ }
+ } while (any_satisfied);
+
+ return ret;
+ }
+
+ struct pseudo_merge *pseudo_merge_for_parents(const struct pseudo_merge_map *pm,
+ struct bitmap *parents)
+ {
+ struct pseudo_merge *match = NULL;
+ size_t i;
+
+ if (!pm->nr)
+ return NULL;
+
+ /*
+ * NOTE: this loop is quadratic in the worst-case (where no
+ * matching pseudo-merge bitmaps are found), but in practice
+ * this is OK for a few reasons:
+ *
+ * - Rejecting pseudo-merge bitmaps that do not match the
+ * given commit is done quickly (i.e. `bitmap_equals_ewah()`
+ * returns early when we know the two bitmaps aren't equal.
+ *
+ * - Already matched pseudo-merge bitmaps (which we track with
+ * the `->satisfied` bit here) are skipped as potential
+ * candidates.
+ *
+ * - The number of pseudo-merges should be small (in the
+ * hundreds for most repositories).
+ *
+ * If in the future this semi-quadratic behavior does become a
+ * problem, another approach would be to keep track of which
+ * pseudo-merges are still "viable" after enumerating the
+ * pseudo-merge commit's parents:
+ *
+ * - A pseudo-merge bitmap becomes non-viable when the bit(s)
+ * corresponding to one or more parent(s) of the given
+ * commit are not set in a candidate pseudo-merge's commits
+ * bitmap.
+ *
+ * - After processing all bits, enumerate the remaining set of
+ * viable pseudo-merge bitmaps, and check that their
+ * popcount() matches the number of parents in the given
+ * commit.
+ */
+ for (i = 0; i < pm->nr; i++) {
+ struct pseudo_merge *candidate = use_pseudo_merge(pm, &pm->v[i]);
+ if (!candidate || candidate->satisfied)
+ continue;
+ if (!bitmap_equals_ewah(parents, candidate->commits))
+ continue;
+
+ match = candidate;
+ match->satisfied = 1;
+ break;
+ }
+
+ return match;
+ }
projects / thirdparty / git.git / commitdiff
