Merge branch 'nd/commit-util-to-slab'

The in-core "commit" object had an all-purpose "void *util" field,
which was tricky to use especially in library-ish part of the
code.  All of the existing uses of the field has been migrated to a
more dedicated "commit-slab" mechanism and the field is eliminated.

* nd/commit-util-to-slab:
  commit.h: delete 'util' field in struct commit
  merge: use commit-slab in merge remote desc instead of commit->util
  log: use commit-slab in prepare_bases() instead of commit->util
  show-branch: note about its object flags usage
  show-branch: use commit-slab for commit-name instead of commit->util
  name-rev: use commit-slab for rev-name instead of commit->util
  bisect.c: use commit-slab for commit weight instead of commit->util
  revision.c: use commit-slab for show_source
  sequencer.c: use commit-slab to associate todo items to commits
  sequencer.c: use commit-slab to mark seen commits
  shallow.c: use commit-slab for commit depth instead of commit->util
  describe: use commit-slab for commit names instead of commit->util
  blame: use commit-slab for blame suspects instead of commit->util
  commit-slab: support shared commit-slab
  commit-slab.h: code split

bisect.c

@@ -12,6 +12,7 @@
 #include "bisect.h"
 #include "sha1-array.h"
 #include "argv-array.h"
+#include "commit-slab.h"
 
 static struct oid_array good_revs;
 static struct oid_array skipped_revs;
@@ -70,16 +71,19 @@ static void clear_distance(struct commit_list *list)
 	}
 }
 
+define_commit_slab(commit_weight, int *);
+static struct commit_weight commit_weight;
+
 #define DEBUG_BISECT 0
 
 static inline int weight(struct commit_list *elem)
 {
-	return *((int*)(elem->item->util));
+	return **commit_weight_at(&commit_weight, elem->item);
 }
 
 static inline void weight_set(struct commit_list *elem, int weight)
 {
-	*((int*)(elem->item->util)) = weight;
+	**commit_weight_at(&commit_weight, elem->item) = weight;
 }
 
 static int count_interesting_parents(struct commit *commit)
@@ -265,7 +269,7 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 		struct commit *commit = p->item;
 		unsigned flags = commit->object.flags;
 
-		p->item->util = &weights[n++];
+		*commit_weight_at(&commit_weight, p->item) = &weights[n++];
 		switch (count_interesting_parents(commit)) {
 		case 0:
 			if (!(flags & TREESAME)) {
@@ -372,6 +376,7 @@ void find_bisection(struct commit_list **commit_list, int *reaches,
 	int *weights;
 
 	show_list("bisection 2 entry", 0, 0, *commit_list);
+	init_commit_weight(&commit_weight);
 
 	/*
 	 * Count the number of total and tree-changing items on the
@@ -412,6 +417,7 @@ void find_bisection(struct commit_list **commit_list, int *reaches,
 	}
 	free(weights);
 	*commit_list = best;
+	clear_commit_weight(&commit_weight);
 }
 
 static int register_ref(const char *refname, const struct object_id *oid,

blame.c

@@ -6,6 +6,24 @@
 #include "diffcore.h"
 #include "tag.h"
 #include "blame.h"
+#include "commit-slab.h"
+
+define_commit_slab(blame_suspects, struct blame_origin *);
+static struct blame_suspects blame_suspects;
+
+struct blame_origin *get_blame_suspects(struct commit *commit)
+{
+	struct blame_origin **result;
+
+	result = blame_suspects_peek(&blame_suspects, commit);
+
+	return result ? *result : NULL;
+}
+
+static void set_blame_suspects(struct commit *commit, struct blame_origin *origin)
+{
+	*blame_suspects_at(&blame_suspects, commit) = origin;
+}
 
 void blame_origin_decref(struct blame_origin *o)
 {
@@ -15,12 +33,12 @@ void blame_origin_decref(struct blame_origin *o)
 			blame_origin_decref(o->previous);
 		free(o->file.ptr);
 		/* Should be present exactly once in commit chain */
-		for (p = o->commit->util; p; l = p, p = p->next) {
+		for (p = get_blame_suspects(o->commit); p; l = p, p = p->next) {
 			if (p == o) {
 				if (l)
 					l->next = p->next;
 				else
-					o->commit->util = p->next;
+					set_blame_suspects(o->commit, p->next);
 				free(o);
 				return;
 			}
@@ -41,8 +59,8 @@ static struct blame_origin *make_origin(struct commit *commit, const char *path)
 	FLEX_ALLOC_STR(o, path, path);
 	o->commit = commit;
 	o->refcnt = 1;
-	o->next = commit->util;
+	o->next = get_blame_suspects(commit);
-	commit->util = o;
+	set_blame_suspects(commit, o);
 	return o;
 }
 
@@ -54,13 +72,13 @@ static struct blame_origin *get_origin(struct commit *commit, const char *path)
 {
 	struct blame_origin *o, *l;
 
-	for (o = commit->util, l = NULL; o; l = o, o = o->next) {
+	for (o = get_blame_suspects(commit), l = NULL; o; l = o, o = o->next) {
 		if (!strcmp(o->path, path)) {
 			/* bump to front */
 			if (l) {
 				l->next = o->next;
-				o->next = commit->util;
+				o->next = get_blame_suspects(commit);
-				commit->util = o;
+				set_blame_suspects(commit, o);
 			}
 			return blame_origin_incref(o);
 		}
@@ -478,7 +496,7 @@ static void queue_blames(struct blame_scoreboard *sb, struct blame_origin *porig
 		porigin->suspects = blame_merge(porigin->suspects, sorted);
 	else {
 		struct blame_origin *o;
-		for (o = porigin->commit->util; o; o = o->next) {
+		for (o = get_blame_suspects(porigin->commit); o; o = o->next) {
 			if (o->suspects) {
 				porigin->suspects = sorted;
 				return;
@@ -525,7 +543,7 @@ static struct blame_origin *find_origin(struct commit *parent,
 	const char *paths[2];
 
 	/* First check any existing origins */
-	for (porigin = parent->util; porigin; porigin = porigin->next)
+	for (porigin = get_blame_suspects(parent); porigin; porigin = porigin->next)
 		if (!strcmp(porigin->path, origin->path)) {
 			/*
 			 * The same path between origin and its parent
@@ -1550,7 +1568,7 @@ void assign_blame(struct blame_scoreboard *sb, int opt)
 
 	while (commit) {
 		struct blame_entry *ent;
-		struct blame_origin *suspect = commit->util;
+		struct blame_origin *suspect = get_blame_suspects(commit);
 
 		/* find one suspect to break down */
 		while (suspect && !suspect->suspects)
@@ -1752,6 +1770,8 @@ void setup_scoreboard(struct blame_scoreboard *sb, const char *path, struct blam
 	struct commit *final_commit = NULL;
 	enum object_type type;
 
+	init_blame_suspects(&blame_suspects);
+
 	if (sb->reverse && sb->contents_from)
 		die(_("--contents and --reverse do not blend well."));
 
@@ -1815,7 +1835,7 @@ void setup_scoreboard(struct blame_scoreboard *sb, const char *path, struct blam
 	}
 
 	if (is_null_oid(&sb->final->object.oid)) {
-		o = sb->final->util;
+		o = get_blame_suspects(sb->final);
 		sb->final_buf = xmemdupz(o->file.ptr, o->file.size);
 		sb->final_buf_size = o->file.size;
 	}

blame.h

@@ -172,4 +172,6 @@ extern void setup_scoreboard(struct blame_scoreboard *sb, const char *path, stru
 
 extern struct blame_entry *blame_entry_prepend(struct blame_entry *head, long start, long end, struct blame_origin *o);
 
+extern struct blame_origin *get_blame_suspects(struct commit *commit);
+
 #endif /* BLAME_H */

builtin/blame.c

@@ -543,7 +543,7 @@ static void output(struct blame_scoreboard *sb, int option)
 			struct commit *commit = ent->suspect->commit;
 			if (commit->object.flags & MORE_THAN_ONE_PATH)
 				continue;
-			for (suspect = commit->util; suspect; suspect = suspect->next) {
+			for (suspect = get_blame_suspects(commit); suspect; suspect = suspect->next) {
 				if (suspect->guilty && count++) {
 					commit->object.flags |= MORE_THAN_ONE_PATH;
 					break;

builtin/describe.c

@@ -15,9 +15,12 @@
 #include "run-command.h"
 #include "revision.h"
 #include "list-objects.h"
+#include "commit-slab.h"
 
 #define MAX_TAGS	(FLAG_BITS - 1)
 
+define_commit_slab(commit_names, struct commit_name *);
+
 static const char * const describe_usage[] = {
 	N_("git describe [<options>] [<commit-ish>...]"),
 	N_("git describe [<options>] --dirty"),
@@ -37,6 +40,7 @@ static struct string_list patterns = STRING_LIST_INIT_NODUP;
 static struct string_list exclude_patterns = STRING_LIST_INIT_NODUP;
 static int always;
 static const char *suffix, *dirty, *broken;
+static struct commit_names commit_names;
 
 /* diff-index command arguments to check if working tree is dirty. */
 static const char *diff_index_args[] = {
@@ -321,11 +325,14 @@ static void describe_commit(struct object_id *oid, struct strbuf *dst)
 	if (!have_util) {
 		struct hashmap_iter iter;
 		struct commit *c;
-		struct commit_name *n = hashmap_iter_first(&names, &iter);
+		struct commit_name *n;
+
+		init_commit_names(&commit_names);
+		n = hashmap_iter_first(&names, &iter);
 		for (; n; n = hashmap_iter_next(&iter)) {
 			c = lookup_commit_reference_gently(&n->peeled, 1);
 			if (c)
-				c->util = n;
+				*commit_names_at(&commit_names, c) = n;
 		}
 		have_util = 1;
 	}
@@ -336,8 +343,11 @@ static void describe_commit(struct object_id *oid, struct strbuf *dst)
 	while (list) {
 		struct commit *c = pop_commit(&list);
 		struct commit_list *parents = c->parents;
+		struct commit_name **slot;
+
 		seen_commits++;
-		n = c->util;
+		slot = commit_names_peek(&commit_names, c);
+		n = slot ? *slot : NULL;
 		if (n) {
 			if (!tags && !all && n->prio < 2) {
 				unannotated_cnt++;

builtin/fast-export.c

@@ -22,6 +22,7 @@
 #include "quote.h"
 #include "remote.h"
 #include "blob.h"
+#include "commit-slab.h"
 
 static const char *fast_export_usage[] = {
 	N_("git fast-export [rev-list-opts]"),
@@ -38,6 +39,7 @@ static int full_tree;
 static struct string_list extra_refs = STRING_LIST_INIT_NODUP;
 static struct refspec refspecs = REFSPEC_INIT_FETCH;
 static int anonymize;
+static struct revision_sources revision_sources;
 
 static int parse_opt_signed_tag_mode(const struct option *opt,
 				     const char *arg, int unset)
@@ -589,7 +591,7 @@ static void handle_commit(struct commit *commit, struct rev_info *rev,
 		if (!S_ISGITLINK(diff_queued_diff.queue[i]->two->mode))
 			export_blob(&diff_queued_diff.queue[i]->two->oid);
 
-	refname = commit->util;
+	refname = *revision_sources_at(&revision_sources, commit);
 	if (anonymize) {
 		refname = anonymize_refname(refname);
 		anonymize_ident_line(&committer, &committer_end);
@@ -861,10 +863,11 @@ static void get_tags_and_duplicates(struct rev_cmdline_info *info)
 		 * This ref will not be updated through a commit, lets make
 		 * sure it gets properly updated eventually.
 		 */
-		if (commit->util || commit->object.flags & SHOWN)
+		if (*revision_sources_at(&revision_sources, commit) ||
+		    commit->object.flags & SHOWN)
 			string_list_append(&extra_refs, full_name)->util = commit;
-		if (!commit->util)
+		if (!*revision_sources_at(&revision_sources, commit))
-			commit->util = full_name;
+			*revision_sources_at(&revision_sources, commit) = full_name;
 	}
 }
 
@@ -1028,8 +1031,9 @@ int cmd_fast_export(int argc, const char **argv, const char *prefix)
 	git_config(git_default_config, NULL);
 
 	init_revisions(&revs, prefix);
+	init_revision_sources(&revision_sources);
 	revs.topo_order = 1;
-	revs.show_source = 1;
+	revs.sources = &revision_sources;
 	revs.rewrite_parents = 1;
 	argc = parse_options(argc, argv, prefix, options, fast_export_usage,
 			PARSE_OPT_KEEP_ARGV0 | PARSE_OPT_KEEP_UNKNOWN);

builtin/log.c

@@ -28,6 +28,7 @@
 #include "mailmap.h"
 #include "gpg-interface.h"
 #include "progress.h"
+#include "commit-slab.h"
 
 #define MAIL_DEFAULT_WRAP 72
 
@@ -148,6 +149,7 @@ static void cmd_log_init_finish(int argc, const char **argv, const char *prefix,
 	static struct string_list decorate_refs_include = STRING_LIST_INIT_NODUP;
 	struct decoration_filter decoration_filter = {&decorate_refs_include,
 						      &decorate_refs_exclude};
+	static struct revision_sources revision_sources;
 
 	const struct option builtin_log_options[] = {
 		OPT__QUIET(&quiet, N_("suppress diff output")),
@@ -194,8 +196,10 @@ static void cmd_log_init_finish(int argc, const char **argv, const char *prefix,
 	    rev->diffopt.filter || rev->diffopt.flags.follow_renames)
 		rev->always_show_header = 0;
 
-	if (source)
+	if (source) {
-		rev->show_source = 1;
+		init_revision_sources(&revision_sources);
+		rev->sources = &revision_sources;
+	}
 
 	if (mailmap) {
 		rev->mailmap = xcalloc(1, sizeof(struct string_list));
@@ -1337,6 +1341,8 @@ static struct commit *get_base_commit(const char *base_commit,
 	return base;
 }
 
+define_commit_slab(commit_base, int);
+
 static void prepare_bases(struct base_tree_info *bases,
 			  struct commit *base,
 			  struct commit **list,
@@ -1345,11 +1351,13 @@ static void prepare_bases(struct base_tree_info *bases,
 	struct commit *commit;
 	struct rev_info revs;
 	struct diff_options diffopt;
+	struct commit_base commit_base;
 	int i;
 
 	if (!base)
 		return;
 
+	init_commit_base(&commit_base);
 	diff_setup(&diffopt);
 	diffopt.flags.recursive = 1;
 	diff_setup_done(&diffopt);
@@ -1362,7 +1370,7 @@ static void prepare_bases(struct base_tree_info *bases,
 	for (i = 0; i < total; i++) {
 		list[i]->object.flags &= ~UNINTERESTING;
 		add_pending_object(&revs, &list[i]->object, "rev_list");
-		list[i]->util = (void *)1;
+		*commit_base_at(&commit_base, list[i]) = 1;
 	}
 	base->object.flags |= UNINTERESTING;
 	add_pending_object(&revs, &base->object, "base");
@@ -1376,7 +1384,7 @@ static void prepare_bases(struct base_tree_info *bases,
 	while ((commit = get_revision(&revs)) != NULL) {
 		struct object_id oid;
 		struct object_id *patch_id;
-		if (commit->util)
+		if (*commit_base_at(&commit_base, commit))
 			continue;
 		if (commit_patch_id(commit, &diffopt, &oid, 0))
 			die(_("cannot get patch id"));
@@ -1385,6 +1393,7 @@ static void prepare_bases(struct base_tree_info *bases,
 		oidcpy(patch_id, &oid);
 		bases->nr_patch_id++;
 	}
+	clear_commit_base(&commit_base);
 }
 
 static void print_bases(struct base_tree_info *bases, FILE *file)

builtin/merge.c

@@ -445,6 +445,7 @@ static void merge_name(const char *remote, struct strbuf *msg)
 	struct object_id branch_head;
 	struct strbuf buf = STRBUF_INIT;
 	struct strbuf bname = STRBUF_INIT;
+	struct merge_remote_desc *desc;
 	const char *ptr;
 	char *found_ref;
 	int len, early;
@@ -517,8 +518,6 @@ static void merge_name(const char *remote, struct strbuf *msg)
 		strbuf_release(&truname);
 	}
 
-	if (remote_head->util) {
-		struct merge_remote_desc *desc;
 	desc = merge_remote_util(remote_head);
 	if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
 		strbuf_addf(msg, "%s\t\t%s '%s'\n",
@@ -527,7 +526,6 @@ static void merge_name(const char *remote, struct strbuf *msg)
 			    remote);
 		goto cleanup;
 	}
-	}
 
 	strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 		oid_to_hex(&remote_head->object.oid), remote);
@@ -934,8 +932,11 @@ static void write_merge_heads(struct commit_list *remoteheads)
 	for (j = remoteheads; j; j = j->next) {
 		struct object_id *oid;
 		struct commit *c = j->item;
-		if (c->util && merge_remote_util(c)->obj) {
+		struct merge_remote_desc *desc;
-			oid = &merge_remote_util(c)->obj->oid;
+
+		desc = merge_remote_util(c);
+		if (desc && desc->obj) {
+			oid = &desc->obj->oid;
 		} else {
 			oid = &c->object.oid;
 		}

builtin/name-rev.c

@@ -6,6 +6,7 @@
 #include "refs.h"
 #include "parse-options.h"
 #include "sha1-lookup.h"
+#include "commit-slab.h"
 
 #define CUTOFF_DATE_SLOP 86400 /* one day */
 
@@ -17,11 +18,26 @@ typedef struct rev_name {
 	int from_tag;
 } rev_name;
 
+define_commit_slab(commit_rev_name, struct rev_name *);
+
 static timestamp_t cutoff = TIME_MAX;
+static struct commit_rev_name rev_names;
 
 /* How many generations are maximally preferred over _one_ merge traversal? */
 #define MERGE_TRAVERSAL_WEIGHT 65535
 
+static struct rev_name *get_commit_rev_name(struct commit *commit)
+{
+	struct rev_name **slot = commit_rev_name_peek(&rev_names, commit);
+
+	return slot ? *slot : NULL;
+}
+
+static void set_commit_rev_name(struct commit *commit, struct rev_name *name)
+{
+	*commit_rev_name_at(&rev_names, commit) = name;
+}
+
 static int is_better_name(struct rev_name *name,
 			  const char *tip_name,
 			  timestamp_t taggerdate,
@@ -65,7 +81,7 @@ static void name_rev(struct commit *commit,
 		int generation, int distance, int from_tag,
 		int deref)
 {
-	struct rev_name *name = (struct rev_name *)commit->util;
+	struct rev_name *name = get_commit_rev_name(commit);
 	struct commit_list *parents;
 	int parent_number = 1;
 	char *to_free = NULL;
@@ -84,7 +100,7 @@ static void name_rev(struct commit *commit,
 
 	if (name == NULL) {
 		name = xmalloc(sizeof(rev_name));
-		commit->util = name;
+		set_commit_rev_name(commit, name);
 		goto copy_data;
 	} else if (is_better_name(name, tip_name, taggerdate,
 				  generation, distance, from_tag)) {
@@ -296,7 +312,7 @@ static const char *get_rev_name(const struct object *o, struct strbuf *buf)
 	if (o->type != OBJ_COMMIT)
 		return get_exact_ref_match(o);
 	c = (struct commit *) o;
-	n = c->util;
+	n = get_commit_rev_name(c);
 	if (!n)
 		return NULL;
 
@@ -413,6 +429,7 @@ int cmd_name_rev(int argc, const char **argv, const char *prefix)
 		OPT_END(),
 	};
 
+	init_commit_rev_name(&rev_names);
 	git_config(git_default_config, NULL);
 	argc = parse_options(argc, argv, prefix, opts, name_rev_usage, 0);
 	if (all + transform_stdin + !!argc > 1) {

builtin/show-branch.c

@@ -7,6 +7,7 @@
 #include "argv-array.h"
 #include "parse-options.h"
 #include "dir.h"
+#include "commit-slab.h"
 
 static const char* show_branch_usage[] = {
     N_("git show-branch [-a | --all] [-r | --remotes] [--topo-order | --date-order]\n"
@@ -21,6 +22,11 @@ static int showbranch_use_color = -1;
 
 static struct argv_array default_args = ARGV_ARRAY_INIT;
 
+/*
+ * TODO: convert this use of commit->object.flags to commit-slab
+ * instead to store a pointer to ref name directly. Then use the same
+ * UNINTERESTING definition from revision.h here.
+ */
 #define UNINTERESTING	01
 
 #define REV_SHIFT	 2
@@ -59,15 +65,27 @@ struct commit_name {
 	int generation; /* how many parents away from head_name */
 };
 
+define_commit_slab(commit_name_slab, struct commit_name *);
+static struct commit_name_slab name_slab;
+
+static struct commit_name *commit_to_name(struct commit *commit)
+{
+	return *commit_name_slab_at(&name_slab, commit);
+}
+
+
 /* Name the commit as nth generation ancestor of head_name;
  * we count only the first-parent relationship for naming purposes.
  */
 static void name_commit(struct commit *commit, const char *head_name, int nth)
 {
 	struct commit_name *name;
-	if (!commit->util)
+
-		commit->util = xmalloc(sizeof(struct commit_name));
+	name = *commit_name_slab_at(&name_slab, commit);
-	name = commit->util;
+	if (!name) {
+		name = xmalloc(sizeof(*name));
+		*commit_name_slab_at(&name_slab, commit) = name;
+	}
 	name->head_name = head_name;
 	name->generation = nth;
 }
@@ -79,8 +97,8 @@ static void name_commit(struct commit *commit, const char *head_name, int nth)
  */
 static void name_parent(struct commit *commit, struct commit *parent)
 {
-	struct commit_name *commit_name = commit->util;
+	struct commit_name *commit_name = commit_to_name(commit);
-	struct commit_name *parent_name = parent->util;
+	struct commit_name *parent_name = commit_to_name(parent);
 	if (!commit_name)
 		return;
 	if (!parent_name ||
@@ -94,12 +112,12 @@ static int name_first_parent_chain(struct commit *c)
 	int i = 0;
 	while (c) {
 		struct commit *p;
-		if (!c->util)
+		if (!commit_to_name(c))
 			break;
 		if (!c->parents)
 			break;
 		p = c->parents->item;
-		if (!p->util) {
+		if (!commit_to_name(p)) {
 			name_parent(c, p);
 			i++;
 		}
@@ -122,7 +140,7 @@ static void name_commits(struct commit_list *list,
 	/* First give names to the given heads */
 	for (cl = list; cl; cl = cl->next) {
 		c = cl->item;
-		if (c->util)
+		if (commit_to_name(c))
 			continue;
 		for (i = 0; i < num_rev; i++) {
 			if (rev[i] == c) {
@@ -148,9 +166,9 @@ static void name_commits(struct commit_list *list,
 			struct commit_name *n;
 			int nth;
 			c = cl->item;
-			if (!c->util)
+			if (!commit_to_name(c))
 				continue;
-			n = c->util;
+			n = commit_to_name(c);
 			parents = c->parents;
 			nth = 0;
 			while (parents) {
@@ -158,7 +176,7 @@ static void name_commits(struct commit_list *list,
 				struct strbuf newname = STRBUF_INIT;
 				parents = parents->next;
 				nth++;
-				if (p->util)
+				if (commit_to_name(p))
 					continue;
 				switch (n->generation) {
 				case 0:
@@ -271,7 +289,7 @@ static void show_one_commit(struct commit *commit, int no_name)
 {
 	struct strbuf pretty = STRBUF_INIT;
 	const char *pretty_str = "(unavailable)";
-	struct commit_name *name = commit->util;
+	struct commit_name *name = commit_to_name(commit);
 
 	if (commit->object.parsed) {
 		pp_commit_easy(CMIT_FMT_ONELINE, commit, &pretty);
@@ -660,6 +678,8 @@ int cmd_show_branch(int ac, const char **av, const char *prefix)
 		OPT_END()
 	};
 
+	init_commit_name_slab(&name_slab);
+
 	git_config(git_show_branch_config, NULL);
 
 	/* If nothing is specified, try the default first */

commit-slab-decl.h

@@ -0,0 +1,43 @@
+#ifndef COMMIT_SLAB_HDR_H
+#define COMMIT_SLAB_HDR_H
+
+/* allocate ~512kB at once, allowing for malloc overhead */
+#ifndef COMMIT_SLAB_SIZE
+#define COMMIT_SLAB_SIZE (512*1024-32)
+#endif
+
+#define declare_commit_slab(slabname, elemtype) 			\
+									\
+struct slabname {							\
+	unsigned slab_size;						\
+	unsigned stride;						\
+	unsigned slab_count;						\
+	elemtype **slab;						\
+}
+
+/*
+ * Statically initialize a commit slab named "var". Note that this
+ * evaluates "stride" multiple times! Example:
+ *
+ *   struct indegree indegrees = COMMIT_SLAB_INIT(1, indegrees);
+ *
+ */
+#define COMMIT_SLAB_INIT(stride, var) { \
+	COMMIT_SLAB_SIZE / sizeof(**((var).slab)) / (stride), \
+	(stride), 0, NULL \
+}
+
+#define declare_commit_slab_prototypes(slabname, elemtype)		\
+									\
+void init_ ##slabname## _with_stride(struct slabname *s, unsigned stride); \
+void init_ ##slabname(struct slabname *s);				\
+void clear_ ##slabname(struct slabname *s);				\
+elemtype *slabname## _at_peek(struct slabname *s, const struct commit *c, int add_if_missing); \
+elemtype *slabname## _at(struct slabname *s, const struct commit *c);	\
+elemtype *slabname## _peek(struct slabname *s, const struct commit *c)
+
+#define define_shared_commit_slab(slabname, elemtype) \
+	declare_commit_slab(slabname, elemtype); \
+	declare_commit_slab_prototypes(slabname, elemtype)
+
+#endif /* COMMIT_SLAB_HDR_H */

commit-slab-impl.h

@@ -0,0 +1,97 @@
+#ifndef COMMIT_SLAB_IMPL_H
+#define COMMIT_SLAB_IMPL_H
+
+#define MAYBE_UNUSED __attribute__((__unused__))
+
+#define implement_static_commit_slab(slabname, elemtype) \
+	implement_commit_slab(slabname, elemtype, static MAYBE_UNUSED)
+
+#define implement_shared_commit_slab(slabname, elemtype) \
+	implement_commit_slab(slabname, elemtype, )
+
+#define implement_commit_slab(slabname, elemtype, scope)		\
+									\
+static int stat_ ##slabname## realloc;					\
+									\
+scope void init_ ##slabname## _with_stride(struct slabname *s,		\
+						   unsigned stride)	\
+{									\
+	unsigned int elem_size;						\
+	if (!stride)							\
+		stride = 1;						\
+	s->stride = stride;						\
+	elem_size = sizeof(elemtype) * stride;				\
+	s->slab_size = COMMIT_SLAB_SIZE / elem_size;			\
+	s->slab_count = 0;						\
+	s->slab = NULL;							\
+}									\
+									\
+scope void init_ ##slabname(struct slabname *s)				\
+{									\
+	init_ ##slabname## _with_stride(s, 1);				\
+}									\
+									\
+scope void clear_ ##slabname(struct slabname *s)			\
+{									\
+	unsigned int i;							\
+	for (i = 0; i < s->slab_count; i++)				\
+		free(s->slab[i]);					\
+	s->slab_count = 0;						\
+	FREE_AND_NULL(s->slab);						\
+}									\
+									\
+scope elemtype *slabname## _at_peek(struct slabname *s,			\
+						  const struct commit *c, \
+						  int add_if_missing)   \
+{									\
+	unsigned int nth_slab, nth_slot;				\
+									\
+	nth_slab = c->index / s->slab_size;				\
+	nth_slot = c->index % s->slab_size;				\
+									\
+	if (s->slab_count <= nth_slab) {				\
+		unsigned int i;						\
+		if (!add_if_missing)					\
+			return NULL;					\
+		REALLOC_ARRAY(s->slab, nth_slab + 1);			\
+		stat_ ##slabname## realloc++;				\
+		for (i = s->slab_count; i <= nth_slab; i++)		\
+			s->slab[i] = NULL;				\
+		s->slab_count = nth_slab + 1;				\
+	}								\
+	if (!s->slab[nth_slab]) {					\
+		if (!add_if_missing)					\
+			return NULL;					\
+		s->slab[nth_slab] = xcalloc(s->slab_size,		\
+					    sizeof(**s->slab) * s->stride);		\
+	}								\
+	return &s->slab[nth_slab][nth_slot * s->stride];		\
+}									\
+									\
+scope elemtype *slabname## _at(struct slabname *s,			\
+					     const struct commit *c)	\
+{									\
+	return slabname##_at_peek(s, c, 1);				\
+}									\
+									\
+scope elemtype *slabname## _peek(struct slabname *s,			\
+					     const struct commit *c)	\
+{									\
+	return slabname##_at_peek(s, c, 0);				\
+}									\
+									\
+struct slabname
+
+/*
+ * Note that this redundant forward declaration is required
+ * to allow a terminating semicolon, which makes instantiations look
+ * like function declarations.  I.e., the expansion of
+ *
+ *    implement_commit_slab(indegree, int, static);
+ *
+ * ends in 'struct indegree;'.  This would otherwise
+ * be a syntax error according (at least) to ISO C.  It's hard to
+ * catch because GCC silently parses it by default.
+ */
+
+#endif	/* COMMIT_SLAB_IMPL_H */

commit-slab.h

@@ -1,6 +1,9 @@
 #ifndef COMMIT_SLAB_H
 #define COMMIT_SLAB_H
 
+#include "commit-slab-decl.h"
+#include "commit-slab-impl.h"
+
 /*
  * define_commit_slab(slabname, elemtype) creates boilerplate code to define
  * a new struct (struct slabname) that is used to associate a piece of data
@@ -41,114 +44,8 @@
  *   leaking memory.
  */
 
-/* allocate ~512kB at once, allowing for malloc overhead */
-#ifndef COMMIT_SLAB_SIZE
-#define COMMIT_SLAB_SIZE (512*1024-32)
-#endif
-
-#define MAYBE_UNUSED __attribute__((__unused__))
-
 #define define_commit_slab(slabname, elemtype) \
-									\
+	declare_commit_slab(slabname, elemtype); \
-struct slabname {							\
+	implement_static_commit_slab(slabname, elemtype)
-	unsigned slab_size;						\
-	unsigned stride;						\
-	unsigned slab_count;						\
-	elemtype **slab;						\
-};									\
-static int stat_ ##slabname## realloc;					\
-									\
-static MAYBE_UNUSED void init_ ##slabname## _with_stride(struct slabname *s, \
-						   unsigned stride)	\
-{									\
-	unsigned int elem_size;						\
-	if (!stride)							\
-		stride = 1;						\
-	s->stride = stride;						\
-	elem_size = sizeof(elemtype) * stride;				\
-	s->slab_size = COMMIT_SLAB_SIZE / elem_size;			\
-	s->slab_count = 0;						\
-	s->slab = NULL;							\
-}									\
-									\
-static MAYBE_UNUSED void init_ ##slabname(struct slabname *s)		\
-{									\
-	init_ ##slabname## _with_stride(s, 1);				\
-}									\
-									\
-static MAYBE_UNUSED void clear_ ##slabname(struct slabname *s)		\
-{									\
-	unsigned int i;							\
-	for (i = 0; i < s->slab_count; i++)				\
-		free(s->slab[i]);					\
-	s->slab_count = 0;						\
-	FREE_AND_NULL(s->slab);						\
-}									\
-									\
-static MAYBE_UNUSED elemtype *slabname## _at_peek(struct slabname *s,	\
-						  const struct commit *c, \
-						  int add_if_missing)   \
-{									\
-	unsigned int nth_slab, nth_slot;				\
-									\
-	nth_slab = c->index / s->slab_size;				\
-	nth_slot = c->index % s->slab_size;				\
-									\
-	if (s->slab_count <= nth_slab) {				\
-		unsigned int i;						\
-		if (!add_if_missing)					\
-			return NULL;					\
-		REALLOC_ARRAY(s->slab, nth_slab + 1);			\
-		stat_ ##slabname## realloc++;				\
-		for (i = s->slab_count; i <= nth_slab; i++)		\
-			s->slab[i] = NULL;				\
-		s->slab_count = nth_slab + 1;				\
-	}								\
-	if (!s->slab[nth_slab]) {					\
-		if (!add_if_missing)					\
-			return NULL;					\
-		s->slab[nth_slab] = xcalloc(s->slab_size,		\
-					    sizeof(**s->slab) * s->stride);		\
-	}								\
-	return &s->slab[nth_slab][nth_slot * s->stride];		\
-}									\
-									\
-static MAYBE_UNUSED elemtype *slabname## _at(struct slabname *s,	\
-					     const struct commit *c)	\
-{									\
-	return slabname##_at_peek(s, c, 1);				\
-}									\
-									\
-static MAYBE_UNUSED elemtype *slabname## _peek(struct slabname *s,	\
-					     const struct commit *c)	\
-{									\
-	return slabname##_at_peek(s, c, 0);				\
-}									\
-									\
-struct slabname
-
-/*
- * Note that this redundant forward declaration is required
- * to allow a terminating semicolon, which makes instantiations look
- * like function declarations.  I.e., the expansion of
- *
- *    define_commit_slab(indegree, int);
- *
- * ends in 'struct indegree;'.  This would otherwise
- * be a syntax error according (at least) to ISO C.  It's hard to
- * catch because GCC silently parses it by default.
- */
-
-/*
- * Statically initialize a commit slab named "var". Note that this
- * evaluates "stride" multiple times! Example:
- *
- *   struct indegree indegrees = COMMIT_SLAB_INIT(1, indegrees);
- *
- */
-#define COMMIT_SLAB_INIT(stride, var) { \
-	COMMIT_SLAB_SIZE / sizeof(**((var).slab)) / (stride), \
-	(stride), 0, NULL \
-}
 
 #endif /* COMMIT_SLAB_H */

commit.c

@@ -1605,13 +1605,21 @@ out:
 	return result;
 }
 
+define_commit_slab(merge_desc_slab, struct merge_remote_desc *);
+static struct merge_desc_slab merge_desc_slab = COMMIT_SLAB_INIT(1, merge_desc_slab);
+
+struct merge_remote_desc *merge_remote_util(struct commit *commit)
+{
+	return *merge_desc_slab_at(&merge_desc_slab, commit);
+}
+
 void set_merge_remote_desc(struct commit *commit,
 			   const char *name, struct object *obj)
 {
 	struct merge_remote_desc *desc;
 	FLEX_ALLOC_STR(desc, name, name);
 	desc->obj = obj;
-	commit->util = desc;
+	*merge_desc_slab_at(&merge_desc_slab, commit) = desc;
 }
 
 struct commit *get_merge_parent(const char *name)
@@ -1623,7 +1631,7 @@ struct commit *get_merge_parent(const char *name)
 		return NULL;
 	obj = parse_object(&oid);
 	commit = (struct commit *)peel_to_type(name, 0, obj, OBJ_COMMIT);
-	if (commit && !commit->util)
+	if (commit && !merge_remote_util(commit))
 		set_merge_remote_desc(commit, name, obj);
 	return commit;
 }

commit.h

@@ -16,9 +16,13 @@ struct commit_list {
 	struct commit_list *next;
 };
 
+/*
+ * The size of this struct matters in full repo walk operations like
+ * 'git clone' or 'git gc'. Consider using commit-slab to attach data
+ * to a commit instead of adding new fields here.
+ */
 struct commit {
 	struct object object;
-	void *util;
 	timestamp_t date;
 	struct commit_list *parents;
 
@@ -312,7 +316,7 @@ struct merge_remote_desc {
 	struct object *obj; /* the named object, could be a tag */
 	char name[FLEX_ARRAY];
 };
-#define merge_remote_util(commit) ((struct merge_remote_desc *)((commit)->util))
+extern struct merge_remote_desc *merge_remote_util(struct commit *);
 extern void set_merge_remote_desc(struct commit *commit,
 				  const char *name, struct object *obj);
 

log-tree.c

@@ -295,8 +295,12 @@ void show_decorations(struct rev_info *opt, struct commit *commit)
 {
 	struct strbuf sb = STRBUF_INIT;
 
-	if (opt->show_source && commit->util)
+	if (opt->sources) {
-		fprintf(opt->diffopt.file, "\t%s", (char *) commit->util);
+		char **slot = revision_sources_peek(opt->sources, commit);
+
+		if (slot && *slot)
+			fprintf(opt->diffopt.file, "\t%s", *slot);
+	}
 	if (!opt->show_decorations)
 		return;
 	format_decorations(&sb, commit, opt->diffopt.use_color);

merge-recursive.c

@@ -286,10 +286,12 @@ static void output(struct merge_options *o, int v, const char *fmt, ...)
 
 static void output_commit_title(struct merge_options *o, struct commit *commit)
 {
+	struct merge_remote_desc *desc;
+
 	strbuf_addchars(&o->obuf, ' ', o->call_depth * 2);
-	if (commit->util)
+	desc = merge_remote_util(commit);
-		strbuf_addf(&o->obuf, "virtual %s\n",
+	if (desc)
-			merge_remote_util(commit)->name);
+		strbuf_addf(&o->obuf, "virtual %s\n", desc->name);
 	else {
 		strbuf_add_unique_abbrev(&o->obuf, &commit->object.oid,
 					 DEFAULT_ABBREV);

object.h

@@ -42,6 +42,7 @@ struct object_array {
  * builtin/index-pack.c:                                     2021
  * builtin/pack-objects.c:                                   20
  * builtin/reflog.c:                   10--12
+ * builtin/show-branch.c:    0-------------------------------------------26
  * builtin/unpack-objects.c:                                 2021
  */
 #define FLAG_BITS  27

revision.c

@@ -29,6 +29,8 @@ volatile show_early_output_fn_t show_early_output;
 static const char *term_bad;
 static const char *term_good;
 
+implement_shared_commit_slab(revision_sources, char *);
+
 void show_object_with_name(FILE *out, struct object *obj, const char *name)
 {
 	const char *p;
@@ -265,14 +267,19 @@ static struct commit *handle_commit(struct rev_info *revs,
 	 */
 	if (object->type == OBJ_COMMIT) {
 		struct commit *commit = (struct commit *)object;
+
 		if (parse_commit(commit) < 0)
 			die("unable to parse commit %s", name);
 		if (flags & UNINTERESTING) {
 			mark_parents_uninteresting(commit);
 			revs->limited = 1;
 		}
-		if (revs->show_source && !commit->util)
+		if (revs->sources) {
-			commit->util = xstrdup(name);
+			char **slot = revision_sources_at(revs->sources, commit);
+
+			if (!*slot)
+				*slot = xstrdup(name);
+		}
 		return commit;
 	}
 
@@ -824,8 +831,12 @@ static int add_parents_to_list(struct rev_info *revs, struct commit *commit,
 			}
 			return -1;
 		}
-		if (revs->show_source && !p->util)
+		if (revs->sources) {
-			p->util = commit->util;
+			char **slot = revision_sources_at(revs->sources, p);
+
+			if (!*slot)
+				*slot = *revision_sources_at(revs->sources, commit);
+		}
 		p->object.flags |= left_flag;
 		if (!(p->object.flags & SEEN)) {
 			p->object.flags |= SEEN;

revision.h

@@ -6,6 +6,7 @@
 #include "notes.h"
 #include "pretty.h"
 #include "diff.h"
+#include "commit-slab-decl.h"
 
 /* Remember to update object flag allocation in object.h */
 #define SEEN		(1u<<0)
@@ -29,6 +30,7 @@ struct rev_info;
 struct log_info;
 struct string_list;
 struct saved_parents;
+define_shared_commit_slab(revision_sources, char *);
 
 struct rev_cmdline_info {
 	unsigned int nr;
@@ -111,7 +113,6 @@ struct rev_info {
 			right_only:1,
 			rewrite_parents:1,
 			print_parents:1,
-			show_source:1,
 			show_decorations:1,
 			reverse:1,
 			reverse_output_stage:1,
@@ -224,6 +225,8 @@ struct rev_info {
 
 	struct commit_list *previous_parents;
 	const char *break_bar;
+
+	struct revision_sources *sources;
 };
 
 extern int ref_excluded(struct string_list *, const char *path);

sequencer.c

@@ -27,6 +27,7 @@
 #include "worktree.h"
 #include "oidmap.h"
 #include "oidset.h"
+#include "commit-slab.h"
 #include "alias.h"
 
 #define GIT_REFLOG_ACTION "GIT_REFLOG_ACTION"
@@ -4238,6 +4239,7 @@ static enum check_level get_missing_commit_check_level(void)
 	return CHECK_IGNORE;
 }
 
+define_commit_slab(commit_seen, unsigned char);
 /*
  * Check if the user dropped some commits by mistake
  * Behaviour determined by rebase.missingCommitsCheck.
@@ -4251,6 +4253,9 @@ int check_todo_list(void)
 	struct todo_list todo_list = TODO_LIST_INIT;
 	struct strbuf missing = STRBUF_INIT;
 	int advise_to_edit_todo = 0, res = 0, i;
+	struct commit_seen commit_seen;
+
+	init_commit_seen(&commit_seen);
 
 	strbuf_addstr(&todo_file, rebase_path_todo());
 	if (strbuf_read_file_or_whine(&todo_list.buf, todo_file.buf) < 0) {
@@ -4267,7 +4272,7 @@ int check_todo_list(void)
 	for (i = 0; i < todo_list.nr; i++) {
 		struct commit *commit = todo_list.items[i].commit;
 		if (commit)
-			commit->util = (void *)1;
+			*commit_seen_at(&commit_seen, commit) = 1;
 	}
 
 	todo_list_release(&todo_list);
@@ -4283,11 +4288,11 @@ int check_todo_list(void)
 	for (i = todo_list.nr - 1; i >= 0; i--) {
 		struct todo_item *item = todo_list.items + i;
 		struct commit *commit = item->commit;
-		if (commit && !commit->util) {
+		if (commit && !*commit_seen_at(&commit_seen, commit)) {
 			strbuf_addf(&missing, " - %s %.*s\n",
 				    short_commit_name(commit),
 				    item->arg_len, item->arg);
-			commit->util = (void *)1;
+			*commit_seen_at(&commit_seen, commit) = 1;
 		}
 	}
 
@@ -4313,6 +4318,7 @@ int check_todo_list(void)
 		"The possible behaviours are: ignore, warn, error.\n\n"));
 
 leave_check:
+	clear_commit_seen(&commit_seen);
 	strbuf_release(&todo_file);
 	todo_list_release(&todo_list);
 
@@ -4433,6 +4439,8 @@ static int subject2item_cmp(const void *fndata,
 	return key ? strcmp(a->subject, key) : strcmp(a->subject, b->subject);
 }
 
+define_commit_slab(commit_todo_item, struct todo_item *);
+
 /*
  * Rearrange the todo list that has both "pick commit-id msg" and "pick
  * commit-id fixup!/squash! msg" in it so that the latter is put immediately
@@ -4449,6 +4457,7 @@ int rearrange_squash(void)
 	struct hashmap subject2item;
 	int res = 0, rearranged = 0, *next, *tail, i;
 	char **subjects;
+	struct commit_todo_item commit_todo;
 
 	if (strbuf_read_file_or_whine(&todo_list.buf, todo_file) < 0)
 		return -1;
@@ -4457,6 +4466,7 @@ int rearrange_squash(void)
 		return -1;
 	}
 
+	init_commit_todo_item(&commit_todo);
 	/*
 	 * The hashmap maps onelines to the respective todo list index.
 	 *
@@ -4487,10 +4497,11 @@ int rearrange_squash(void)
 
 		if (is_fixup(item->command)) {
 			todo_list_release(&todo_list);
+			clear_commit_todo_item(&commit_todo);
 			return error(_("the script was already rearranged."));
 		}
 
-		item->commit->util = item;
+		*commit_todo_item_at(&commit_todo, item->commit) = item;
 
 		parse_commit(item->commit);
 		commit_buffer = get_commit_buffer(item->commit, NULL);
@@ -4517,9 +4528,9 @@ int rearrange_squash(void)
 			else if (!strchr(p, ' ') &&
 				 (commit2 =
 				  lookup_commit_reference_by_name(p)) &&
-				 commit2->util)
+				 *commit_todo_item_at(&commit_todo, commit2))
 				/* found by commit name */
-				i2 = (struct todo_item *)commit2->util
+				i2 = *commit_todo_item_at(&commit_todo, commit2)
 					- todo_list.items;
 			else {
 				/* copy can be a prefix of the commit subject */
@@ -4596,5 +4607,6 @@ int rearrange_squash(void)
 	hashmap_free(&subject2item, 1);
 	todo_list_release(&todo_list);
 
+	clear_commit_todo_item(&commit_todo);
 	return res;
 }

shallow.c

@@ -12,6 +12,7 @@
 #include "commit-slab.h"
 #include "revision.h"
 #include "list-objects.h"
+#include "commit-slab.h"
 
 static int is_shallow = -1;
 static struct stat_validity shallow_stat;
@@ -74,6 +75,11 @@ int is_repository_shallow(void)
 	return is_shallow;
 }
 
+/*
+ * TODO: use "int" elemtype instead of "int *" when/if commit-slab
+ * supports a "valid" flag.
+ */
+define_commit_slab(commit_depth, int *);
 struct commit_list *get_shallow_commits(struct object_array *heads, int depth,
 		int shallow_flag, int not_shallow_flag)
 {
@@ -82,25 +88,29 @@ struct commit_list *get_shallow_commits(struct object_array *heads, int depth,
 	struct object_array stack = OBJECT_ARRAY_INIT;
 	struct commit *commit = NULL;
 	struct commit_graft *graft;
+	struct commit_depth depths;
 
+	init_commit_depth(&depths);
 	while (commit || i < heads->nr || stack.nr) {
 		struct commit_list *p;
 		if (!commit) {
 			if (i < heads->nr) {
+				int **depth_slot;
 				commit = (struct commit *)
 					deref_tag(heads->objects[i++].item, NULL, 0);
 				if (!commit || commit->object.type != OBJ_COMMIT) {
 					commit = NULL;
 					continue;
 				}
-				if (!commit->util)
+				depth_slot = commit_depth_at(&depths, commit);
-					commit->util = xmalloc(sizeof(int));
+				if (!*depth_slot)
-				*(int *)commit->util = 0;
+					*depth_slot = xmalloc(sizeof(int));
+				**depth_slot = 0;
 				cur_depth = 0;
 			} else {
 				commit = (struct commit *)
 					object_array_pop(&stack);
-				cur_depth = *(int *)commit->util;
+				cur_depth = **commit_depth_at(&depths, commit);
 			}
 		}
 		parse_commit_or_die(commit);
@@ -116,25 +126,31 @@ struct commit_list *get_shallow_commits(struct object_array *heads, int depth,
 		}
 		commit->object.flags |= not_shallow_flag;
 		for (p = commit->parents, commit = NULL; p; p = p->next) {
-			if (!p->item->util) {
+			int **depth_slot = commit_depth_at(&depths, p->item);
-				int *pointer = xmalloc(sizeof(int));
+			if (!*depth_slot) {
-				p->item->util = pointer;
+				*depth_slot = xmalloc(sizeof(int));
-				*pointer =  cur_depth;
+				**depth_slot = cur_depth;
 			} else {
-				int *pointer = p->item->util;
+				if (cur_depth >= **depth_slot)
-				if (cur_depth >= *pointer)
 					continue;
-				*pointer = cur_depth;
+				**depth_slot = cur_depth;
 			}
 			if (p->next)
 				add_object_array(&p->item->object,
 						NULL, &stack);
 			else {
 				commit = p->item;
-				cur_depth = *(int *)commit->util;
+				cur_depth = **commit_depth_at(&depths, commit);
 			}
 		}
 	}
+	for (i = 0; i < depths.slab_count; i++) {
+		int j;
+
+		for (j = 0; j < depths.slab_size; j++)
+			free(depths.slab[i][j]);
+	}
+	clear_commit_depth(&depths);
 
 	return result;
 }