Store peeled refs in packed-refs file.

This would speed up "show-ref -d" in a repository with mostly
packed tags.

Signed-off-by: Junio C Hamano <junkio@cox.net>

builtin-pack-refs.c

@@ -1,5 +1,7 @@
 #include "cache.h"
 #include "refs.h"
+#include "object.h"
+#include "tag.h"
 
 static const char builtin_pack_refs_usage[] =
 "git-pack-refs [--all] [--prune]";
@@ -29,12 +31,26 @@ static int handle_one_ref(const char *path, const unsigned char *sha1,
 			  int flags, void *cb_data)
 {
 	struct pack_refs_cb_data *cb = cb_data;
+	int is_tag_ref;
 
-	if (!cb->all && strncmp(path, "refs/tags/", 10))
-		return 0;
 	/* Do not pack the symbolic refs */
-	if (!(flags & REF_ISSYMREF))
-		fprintf(cb->refs_file, "%s %s\n", sha1_to_hex(sha1), path);
+	if ((flags & REF_ISSYMREF))
+		return 0;
+	is_tag_ref = !strncmp(path, "refs/tags/", 10);
+	if (!cb->all && !is_tag_ref)
+		return 0;
+
+	fprintf(cb->refs_file, "%s %s\n", sha1_to_hex(sha1), path);
+	if (is_tag_ref) {
+		struct object *o = parse_object(sha1);
+		if (o->type == OBJ_TAG) {
+			o = deref_tag(o, path, 0);
+			if (o)
+				fprintf(cb->refs_file, "%s  %s^{}\n",
+					sha1_to_hex(o->sha1), path);
+		}
+	}
+
 	if (cb->prune && !do_not_prune(flags)) {
 		int namelen = strlen(path) + 1;
 		struct ref_to_prune *n = xcalloc(1, sizeof(*n) + namelen);

builtin-show-ref.c

@@ -13,6 +13,7 @@ static int show_ref(const char *refname, const unsigned char *sha1, int flag, vo
 {
 	struct object *obj;
 	const char *hex;
+	unsigned char peeled[20];
 
 	if (tags_only || heads_only) {
 		int match;
@@ -44,12 +45,15 @@ static int show_ref(const char *refname, const unsigned char *sha1, int flag, vo
 
 match:
 	found_match++;
-	obj = parse_object(sha1);
-	if (!obj) {
-		if (quiet)
-			return 0;
-		die("git-show-ref: bad ref %s (%s)", refname, sha1_to_hex(sha1));
-	}
+
+	/* This changes the semantics slightly that even under quiet we
+	 * detect and return error if the repository is corrupt and
+	 * ref points at a nonexistent object.
+	 */
+	if (!has_sha1_file(sha1))
+		die("git-show-ref: bad ref %s (%s)", refname,
+		    sha1_to_hex(sha1));
+
 	if (quiet)
 		return 0;
 
@@ -58,11 +62,25 @@ static int show_ref(const char *refname, const unsigned char *sha1, int flag, vo
 		printf("%s\n", hex);
 	else
 		printf("%s %s\n", hex, refname);
-	if (deref_tags && obj->type == OBJ_TAG) {
-		obj = deref_tag(obj, refname, 0);
-		hex = find_unique_abbrev(obj->sha1, abbrev);
+
+	if (!deref_tags)
+		return 0;
+
+	if ((flag & REF_ISPACKED) && !peel_ref(refname, peeled)) {
+		hex = find_unique_abbrev(peeled, abbrev);
 		printf("%s %s^{}\n", hex, refname);
 	}
+	else {
+		obj = parse_object(sha1);
+		if (!obj)
+			die("git-show-ref: bad ref %s (%s)", refname,
+			    sha1_to_hex(sha1));
+		if (obj->type == OBJ_TAG) {
+			obj = deref_tag(obj, refname, 0);
+			hex = find_unique_abbrev(obj->sha1, abbrev);
+			printf("%s %s^{}\n", hex, refname);
+		}
+	}
 	return 0;
 }
 

refs.c

@@ -1,16 +1,18 @@
 #include "refs.h"
 #include "cache.h"
+#include "object.h"
+#include "tag.h"
 
 #include <errno.h>
 
 struct ref_list {
 	struct ref_list *next;
-	unsigned char flag; /* ISSYMREF? ISPACKED? */
+	unsigned char flag; /* ISSYMREF? ISPACKED? ISPEELED? */
 	unsigned char sha1[20];
 	char name[FLEX_ARRAY];
 };
 
-static const char *parse_ref_line(char *line, unsigned char *sha1)
+static const char *parse_ref_line(char *line, unsigned char *sha1, int *flag)
 {
 	/*
 	 * 42: the answer to everything.
@@ -21,6 +23,7 @@ static const char *parse_ref_line(char *line, unsigned char *sha1)
 	 *  +1 (newline at the end of the line)
 	 */
 	int len = strlen(line) - 42;
+	int peeled = 0;
 
 	if (len <= 0)
 		return NULL;
@@ -29,11 +32,24 @@ static const char *parse_ref_line(char *line, unsigned char *sha1)
 	if (!isspace(line[40]))
 		return NULL;
 	line += 41;
-	if (isspace(*line))
-		return NULL;
+
+	if (isspace(*line)) {
+		/* "SHA-1 SP SP refs/tags/tagname^{} LF"? */
+		line++;
+		len--;
+		peeled = 1;
+	}
 	if (line[len] != '\n')
 		return NULL;
 	line[len] = 0;
+
+	if (peeled && (len < 3 || strcmp(line + len - 3, "^{}")))
+		return NULL;
+
+	if (!peeled)
+		*flag &= ~REF_ISPEELED;
+	else
+		*flag |= REF_ISPEELED;
 	return line;
 }
 
@@ -108,10 +124,12 @@ static struct ref_list *get_packed_refs(void)
 			char refline[PATH_MAX];
 			while (fgets(refline, sizeof(refline), f)) {
 				unsigned char sha1[20];
-				const char *name = parse_ref_line(refline, sha1);
+				int flag = REF_ISPACKED;
+				const char *name =
+					parse_ref_line(refline, sha1, &flag);
 				if (!name)
 					continue;
-				list = add_ref(name, sha1, REF_ISPACKED, list);
+				list = add_ref(name, sha1, flag, list);
 			}
 			fclose(f);
 			refs = list;
@@ -207,7 +225,8 @@ const char *resolve_ref(const char *ref, unsigned char *sha1, int reading, int *
 		if (lstat(path, &st) < 0) {
 			struct ref_list *list = get_packed_refs();
 			while (list) {
-				if (!strcmp(ref, list->name)) {
+				if (!(list->flag & REF_ISPEELED) &&
+				    !strcmp(ref, list->name)) {
 					hashcpy(sha1, list->sha1);
 					if (flag)
 						*flag |= REF_ISPACKED;
@@ -329,6 +348,8 @@ static int do_one_ref(const char *base, each_ref_fn fn, int trim,
 		return 0;
 	if (is_null_sha1(entry->sha1))
 		return 0;
+	if (entry->flag & REF_ISPEELED)
+		return 0;
 	if (!has_sha1_file(entry->sha1)) {
 		error("%s does not point to a valid object!", entry->name);
 		return 0;
@@ -336,6 +357,44 @@ static int do_one_ref(const char *base, each_ref_fn fn, int trim,
 	return fn(entry->name + trim, entry->sha1, entry->flag, cb_data);
 }
 
+int peel_ref(const char *ref, unsigned char *sha1)
+{
+	int flag;
+	unsigned char base[20];
+	struct object *o;
+
+	if (!resolve_ref(ref, base, 1, &flag))
+		return -1;
+
+	if ((flag & REF_ISPACKED)) {
+		struct ref_list *list = get_packed_refs();
+		int len = strlen(ref);
+
+		while (list) {
+			if ((list->flag & REF_ISPEELED) &&
+			    !strncmp(list->name, ref, len) &&
+			    strlen(list->name) == len + 3 &&
+			    !strcmp(list->name + len, "^{}")) {
+				hashcpy(sha1, list->sha1);
+				return 0;
+			}
+			list = list->next;
+		}
+		/* older pack-refs did not leave peeled ones in */
+	}
+
+	/* otherwise ... */
+	o = parse_object(base);
+	if (o->type == OBJ_TAG) {
+		o = deref_tag(o, ref, 0);
+		if (o) {
+			hashcpy(sha1, o->sha1);
+			return 0;
+		}
+	}
+	return -1;
+}
+
 static int do_for_each_ref(const char *base, each_ref_fn fn, int trim,
 			   void *cb_data)
 {

refs.h

@@ -16,6 +16,8 @@ struct ref_lock {
  */
 #define REF_ISSYMREF 01
 #define REF_ISPACKED 02
+#define REF_ISPEELED 04 /* internal use */
+
 typedef int each_ref_fn(const char *refname, const unsigned char *sha1, int flags, void *cb_data);
 extern int head_ref(each_ref_fn, void *);
 extern int for_each_ref(each_ref_fn, void *);
@@ -23,6 +25,8 @@ extern int for_each_tag_ref(each_ref_fn, void *);
 extern int for_each_branch_ref(each_ref_fn, void *);
 extern int for_each_remote_ref(each_ref_fn, void *);
 
+extern int peel_ref(const char *, unsigned char *);
+
 /** Reads the refs file specified into sha1 **/
 extern int get_ref_sha1(const char *ref, unsigned char *sha1);