revision.c: update show_object_with_name() without using malloc()

Allocating and then immediately freeing temporary memory a million times
when listing a million objects is distasteful.

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

revision.c

diff --git a/revision.c b/revision.c
index c5b38cc..072ddac 100644
--- a/revision.c
+++ b/revision.c
@@ -40,23 +40,45 @@
 	return n;
 }
 
+static int show_path_component_truncated(FILE *out, const char *name, int len)
+{
+	int cnt;
+	for (cnt = 0; cnt < len; cnt++) {
+		int ch = name[cnt];
+		if (!ch || ch == '\n')
+			return -1;
+		fputc(ch, out);
+	}
+	return len;
+}
+
+static int show_path_truncated(FILE *out, const struct name_path *path)
+{
+	int emitted, ours;
+
+	if (!path)
+		return 0;
+	emitted = show_path_truncated(out, path->up);
+	if (emitted < 0)
+		return emitted;
+	if (emitted)
+		fputc('/', out);
+	ours = show_path_component_truncated(out, path->elem, path->elem_len);
+	if (ours < 0)
+		return ours;
+	return ours || emitted;
+}
+
 void show_object_with_name(FILE *out, struct object *obj, const struct name_path *path, const char *component)
 {
-	char *name = path_name(path, component);
-	const char *ep = strchr(name, '\n');
+	struct name_path leaf;
+	leaf.up = (struct name_path *)path;
+	leaf.elem = component;
+	leaf.elem_len = strlen(component);
 
-	/*
-	 * An object with name "foo\n0000000..." can be used to
-	 * confuse downstream "git pack-objects" very badly.
-	 */
-	if (ep) {
-		fprintf(out, "%s %.*s\n", sha1_to_hex(obj->sha1),
-			(int) (ep - name),
-			name);
-	}
-	else
-		fprintf(out, "%s %s\n", sha1_to_hex(obj->sha1), name);
-	free(name);
+	fprintf(out, "%s ", sha1_to_hex(obj->sha1));
+	show_path_truncated(out, &leaf);
+	fputc('\n', out);
 }
 
 void add_object(struct object *obj,