show-branch: use commit-slab for commit-name instead of commit->util

It's done so that commit->util can be removed. See more explanation in
the commit that removes commit->util.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

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"
@@ -59,15 +60,27 @@ 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->util;
+
+	name = *commit_name_slab_at(&name_slab, commit);
+	if (!name) {
+		name = xmalloc(sizeof(*name));
+		*commit_name_slab_at(&name_slab, commit) = name;
+	}
 	name->head_name = head_name;
 	name->generation = nth;
 }
@@ -79,8 +92,8 @@ 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 *parent_name = parent->util;
+	struct commit_name *commit_name = commit_to_name(commit);
+	struct commit_name *parent_name = commit_to_name(parent);
 	if (!commit_name)
 		return;
 	if (!parent_name ||
@@ -94,12 +107,12 @@ 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 +135,7 @@ 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 +161,9 @@ 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 +171,7 @@ 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 +284,7 @@ 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 +673,8 @@ 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 */