Make ref resolution saner

The old code used to totally mix up the notion of a ref-name and the path
that that ref was associated with.  That was not only horribly ugly (a
number of users got the path, and then wanted to try to turn it back into
a ref-name again), but it fundamnetally doesn't work at all once we do any
setup where a ref doesn't have a 1:1 relationship with a particular
pathname.

This fixes things up so that we use the ref-name throughout, and only
turn it into a pathname once we actually look it up in the filesystem.
That makes a lot of things much clearer and more straightforward.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

7 files changed, 74 insertions, 84 deletions

diff --git a/builtin-fmt-merge-msg.c b/builtin-fmt-merge-msg.c
index c407c033e..b93c17c2f 100644
--- a/builtin-fmt-merge-msg.c
+++ b/builtin-fmt-merge-msg.c
@@ -249,7 +249,7 @@ int cmd_fmt_merge_msg(int argc, const char **argv, const char *prefix)
 	FILE *in = stdin;
 	const char *sep = "";
 	unsigned char head_sha1[20];
-	const char *head, *current_branch;
+	const char *current_branch;
 
 	git_config(fmt_merge_msg_config);
 
@@ -277,10 +277,7 @@ int cmd_fmt_merge_msg(int argc, const char **argv, const char *prefix)
 		usage(fmt_merge_msg_usage);
 
 	/* get current branch */
-	head = xstrdup(git_path("HEAD"));
-	current_branch = resolve_ref(head, head_sha1, 1);
-	current_branch += strlen(head) - 4;
-	free((char *)head);
+	current_branch = resolve_ref("HEAD", head_sha1, 1);
 	if (!strncmp(current_branch, "refs/heads/", 11))
 		current_branch += 11;
 
diff --git a/builtin-init-db.c b/builtin-init-db.c
index 5085018e4..23b7714f8 100644
--- a/builtin-init-db.c
+++ b/builtin-init-db.c
@@ -218,8 +218,8 @@ static void create_default_files(const char *git_dir, const char *template_path)
 	 * branch, if it does not exist yet.
 	 */
 	strcpy(path + len, "HEAD");
-	if (read_ref(path, sha1) < 0) {
-		if (create_symref(path, "refs/heads/master") < 0)
+	if (read_ref("HEAD", sha1) < 0) {
+		if (create_symref("HEAD", "refs/heads/master") < 0)
 			exit(1);
 	}
 
diff --git a/builtin-show-branch.c b/builtin-show-branch.c
index 578c9fafd..4d8db0c10 100644
--- a/builtin-show-branch.c
+++ b/builtin-show-branch.c
@@ -437,21 +437,13 @@ static void snarf_refs(int head, int tag)
 	}
 }
 
-static int rev_is_head(char *head_path, int headlen, char *name,
+static int rev_is_head(char *head, int headlen, char *name,
 		       unsigned char *head_sha1, unsigned char *sha1)
 {
-	int namelen;
-	if ((!head_path[0]) ||
+	if ((!head[0]) ||
 	    (head_sha1 && sha1 && hashcmp(head_sha1, sha1)))
 		return 0;
-	namelen = strlen(name);
-	if ((headlen < namelen) ||
-	    memcmp(head_path + headlen - namelen, name, namelen))
-		return 0;
-	if (headlen == namelen ||
-	    head_path[headlen - namelen - 1] == '/')
-		return 1;
-	return 0;
+	return !strcmp(head, name);
 }
 
 static int show_merge_base(struct commit_list *seen, int num_rev)
@@ -559,9 +551,9 @@ int cmd_show_branch(int ac, const char **av, const char *prefix)
 	int all_heads = 0, all_tags = 0;
 	int all_mask, all_revs;
 	int lifo = 1;
-	char head_path[128];
-	const char *head_path_p;
-	int head_path_len;
+	char head[128];
+	const char *head_p;
+	int head_len;
 	unsigned char head_sha1[20];
 	int merge_base = 0;
 	int independent = 0;
@@ -638,31 +630,31 @@ int cmd_show_branch(int ac, const char **av, const char *prefix)
 		ac--; av++;
 	}
 
-	head_path_p = resolve_ref(git_path("HEAD"), head_sha1, 1);
-	if (head_path_p) {
-		head_path_len = strlen(head_path_p);
-		memcpy(head_path, head_path_p, head_path_len + 1);
+	head_p = resolve_ref("HEAD", head_sha1, 1);
+	if (head_p) {
+		head_len = strlen(head_p);
+		memcpy(head, head_p, head_len + 1);
 	}
 	else {
-		head_path_len = 0;
-		head_path[0] = 0;
+		head_len = 0;
+		head[0] = 0;
 	}
 
-	if (with_current_branch && head_path_p) {
+	if (with_current_branch && head_p) {
 		int has_head = 0;
 		for (i = 0; !has_head && i < ref_name_cnt; i++) {
 			/* We are only interested in adding the branch
 			 * HEAD points at.
 			 */
-			if (rev_is_head(head_path,
-					head_path_len,
+			if (rev_is_head(head,
+					head_len,
 					ref_name[i],
 					head_sha1, NULL))
 				has_head++;
 		}
 		if (!has_head) {
-			int pfxlen = strlen(git_path("refs/heads/"));
-			append_one_rev(head_path + pfxlen);
+			int pfxlen = strlen("refs/heads/");
+			append_one_rev(head + pfxlen);
 		}
 	}
 
@@ -713,8 +705,8 @@ int cmd_show_branch(int ac, const char **av, const char *prefix)
 	if (1 < num_rev || extra < 0) {
 		for (i = 0; i < num_rev; i++) {
 			int j;
-			int is_head = rev_is_head(head_path,
-						  head_path_len,
+			int is_head = rev_is_head(head,
+						  head_len,
 						  ref_name[i],
 						  head_sha1,
 						  rev[i]->object.sha1);
diff --git a/builtin-symbolic-ref.c b/builtin-symbolic-ref.c
index 1d3a5e229..6f18db870 100644
--- a/builtin-symbolic-ref.c
+++ b/builtin-symbolic-ref.c
@@ -7,15 +7,11 @@ static const char git_symbolic_ref_usage[] =
 static void check_symref(const char *HEAD)
 {
 	unsigned char sha1[20];
-	const char *git_HEAD = xstrdup(git_path("%s", HEAD));
-	const char *git_refs_heads_master = resolve_ref(git_HEAD, sha1, 0);
-	if (git_refs_heads_master) {
-		/* we want to strip the .git/ part */
-		int pfxlen = strlen(git_HEAD) - strlen(HEAD);
-		puts(git_refs_heads_master + pfxlen);
-	}
-	else
+	const char *refs_heads_master = resolve_ref("HEAD", sha1, 0);
+
+	if (!refs_heads_master)
 		die("No such ref: %s", HEAD);
+	puts(refs_heads_master);
 }
 
 int cmd_symbolic_ref(int argc, const char **argv, const char *prefix)
@@ -26,7 +22,7 @@ int cmd_symbolic_ref(int argc, const char **argv, const char *prefix)
 		check_symref(argv[1]);
 		break;
 	case 3:
-		create_symref(xstrdup(git_path("%s", argv[1])), argv[2]);
+		create_symref(argv[1], argv[2]);
 		break;
 	default:
 		usage(git_symbolic_ref_usage);
diff --git a/cache.h b/cache.h
index 57db7c9b2..282eed6f0 100644
--- a/cache.h
+++ b/cache.h
@@ -287,8 +287,8 @@ extern int get_sha1_hex(const char *hex, unsigned char *sha1);
 extern char *sha1_to_hex(const unsigned char *sha1);	/* static buffer result! */
 extern int read_ref(const char *filename, unsigned char *sha1);
 extern const char *resolve_ref(const char *path, unsigned char *sha1, int);
-extern int create_symref(const char *git_HEAD, const char *refs_heads_master);
-extern int validate_symref(const char *git_HEAD);
+extern int create_symref(const char *ref, const char *refs_heads_master);
+extern int validate_symref(const char *ref);
 
 extern int base_name_compare(const char *name1, int len1, int mode1, const char *name2, int len2, int mode2);
 extern int cache_name_compare(const char *name1, int len1, const char *name2, int len2);
diff --git a/refs.c b/refs.c
index 72e22834f..50c25d3d2 100644
--- a/refs.c
+++ b/refs.c
@@ -93,11 +93,11 @@ static struct ref_list *get_ref_dir(const char *base, struct ref_list *list)
 	if (dir) {
 		struct dirent *de;
 		int baselen = strlen(base);
-		char *path = xmalloc(baselen + 257);
+		char *ref = xmalloc(baselen + 257);
 
-		memcpy(path, base, baselen);
+		memcpy(ref, base, baselen);
 		if (baselen && base[baselen-1] != '/')
-			path[baselen++] = '/';
+			ref[baselen++] = '/';
 
 		while ((de = readdir(dir)) != NULL) {
 			unsigned char sha1[20];
@@ -111,20 +111,20 @@ static struct ref_list *get_ref_dir(const char *base, struct ref_list *list)
 				continue;
 			if (has_extension(de->d_name, ".lock"))
 				continue;
-			memcpy(path + baselen, de->d_name, namelen+1);
-			if (stat(git_path("%s", path), &st) < 0)
+			memcpy(ref + baselen, de->d_name, namelen+1);
+			if (stat(git_path("%s", ref), &st) < 0)
 				continue;
 			if (S_ISDIR(st.st_mode)) {
-				list = get_ref_dir(path, list);
+				list = get_ref_dir(ref, list);
 				continue;
 			}
-			if (read_ref(git_path("%s", path), sha1) < 0) {
-				error("%s points nowhere!", path);
+			if (read_ref(ref, sha1) < 0) {
+				error("%s points nowhere!", ref);
 				continue;
 			}
-			list = add_ref(path, sha1, list);
+			list = add_ref(ref, sha1, list);
 		}
-		free(path);
+		free(ref);
 		closedir(dir);
 	}
 	return list;
@@ -145,12 +145,14 @@ static struct ref_list *get_loose_refs(void)
 /* We allow "recursive" symbolic refs. Only within reason, though */
 #define MAXDEPTH 5
 
-const char *resolve_ref(const char *path, unsigned char *sha1, int reading)
+const char *resolve_ref(const char *ref, unsigned char *sha1, int reading)
 {
 	int depth = MAXDEPTH, len;
 	char buffer[256];
+	static char ref_buffer[256];
 
 	for (;;) {
+		const char *path = git_path("%s", ref);
 		struct stat st;
 		char *buf;
 		int fd;
@@ -169,14 +171,16 @@ const char *resolve_ref(const char *path, unsigned char *sha1, int reading)
 			if (reading || errno != ENOENT)
 				return NULL;
 			hashclr(sha1);
-			return path;
+			return ref;
 		}
 
 		/* Follow "normalized" - ie "refs/.." symlinks by hand */
 		if (S_ISLNK(st.st_mode)) {
 			len = readlink(path, buffer, sizeof(buffer)-1);
 			if (len >= 5 && !memcmp("refs/", buffer, 5)) {
-				path = git_path("%.*s", len, buffer);
+				buffer[len] = 0;
+				strcpy(ref_buffer, buffer);
+				ref = ref_buffer;
 				continue;
 			}
 		}
@@ -201,19 +205,22 @@ const char *resolve_ref(const char *path, unsigned char *sha1, int reading)
 		while (len && isspace(*buf))
 			buf++, len--;
 		while (len && isspace(buf[len-1]))
-			buf[--len] = 0;
-		path = git_path("%.*s", len, buf);
+			len--;
+		buf[len] = 0;
+		memcpy(ref_buffer, buf, len + 1);
+		ref = ref_buffer;
 	}
 	if (len < 40 || get_sha1_hex(buffer, sha1))
 		return NULL;
-	return path;
+	return ref;
 }
 
-int create_symref(const char *git_HEAD, const char *refs_heads_master)
+int create_symref(const char *ref_target, const char *refs_heads_master)
 {
 	const char *lockpath;
 	char ref[1000];
 	int fd, len, written;
+	const char *git_HEAD = git_path("%s", ref_target);
 
 #ifndef NO_SYMLINK_HEAD
 	if (prefer_symlink_refs) {
@@ -251,9 +258,9 @@ int create_symref(const char *git_HEAD, const char *refs_heads_master)
 	return 0;
 }
 
-int read_ref(const char *filename, unsigned char *sha1)
+int read_ref(const char *ref, unsigned char *sha1)
 {
-	if (resolve_ref(filename, sha1, 1))
+	if (resolve_ref(ref, sha1, 1))
 		return 0;
 	return -1;
 }
@@ -306,7 +313,7 @@ static int do_for_each_ref(const char *base, int (*fn)(const char *path, const u
 int head_ref(int (*fn)(const char *path, const unsigned char *sha1))
 {
 	unsigned char sha1[20];
-	if (!read_ref(git_path("HEAD"), sha1))
+	if (!read_ref("HEAD", sha1))
 		return fn("HEAD", sha1);
 	return 0;
 }
@@ -335,7 +342,7 @@ int get_ref_sha1(const char *ref, unsigned char *sha1)
 {
 	if (check_ref_format(ref))
 		return -1;
-	return read_ref(git_path("refs/%s", ref), sha1);
+	return read_ref(mkpath("refs/%s", ref), sha1);
 }
 
 /*
@@ -416,31 +423,30 @@ static struct ref_lock *verify_lock(struct ref_lock *lock,
 	return lock;
 }
 
-static struct ref_lock *lock_ref_sha1_basic(const char *path,
+static struct ref_lock *lock_ref_sha1_basic(const char *ref,
 	int plen,
 	const unsigned char *old_sha1, int mustexist)
 {
-	const char *orig_path = path;
+	const char *orig_ref = ref;
 	struct ref_lock *lock;
 	struct stat st;
 
 	lock = xcalloc(1, sizeof(struct ref_lock));
 	lock->lock_fd = -1;
 
-	plen = strlen(path) - plen;
-	path = resolve_ref(path, lock->old_sha1, mustexist);
-	if (!path) {
+	ref = resolve_ref(ref, lock->old_sha1, mustexist);
+	if (!ref) {
 		int last_errno = errno;
 		error("unable to resolve reference %s: %s",
-			orig_path, strerror(errno));
+			orig_ref, strerror(errno));
 		unlock_ref(lock);
 		errno = last_errno;
 		return NULL;
 	}
 	lock->lk = xcalloc(1, sizeof(struct lock_file));
 
-	lock->ref_file = xstrdup(path);
-	lock->log_file = xstrdup(git_path("logs/%s", lock->ref_file + plen));
+	lock->ref_file = xstrdup(git_path("%s", ref));
+	lock->log_file = xstrdup(git_path("logs/%s", ref));
 	lock->force_write = lstat(lock->ref_file, &st) && errno == ENOENT;
 
 	if (safe_create_leading_directories(lock->ref_file))
@@ -455,15 +461,14 @@ struct ref_lock *lock_ref_sha1(const char *ref,
 {
 	if (check_ref_format(ref))
 		return NULL;
-	return lock_ref_sha1_basic(git_path("refs/%s", ref),
+	return lock_ref_sha1_basic(mkpath("refs/%s", ref),
 		5 + strlen(ref), old_sha1, mustexist);
 }
 
 struct ref_lock *lock_any_ref_for_update(const char *ref,
 	const unsigned char *old_sha1, int mustexist)
 {
-	return lock_ref_sha1_basic(git_path("%s", ref),
-		strlen(ref), old_sha1, mustexist);
+	return lock_ref_sha1_basic(ref, strlen(ref), old_sha1, mustexist);
 }
 
 void unlock_ref(struct ref_lock *lock)
diff --git a/sha1_name.c b/sha1_name.c
index 1fbc44380..b4975289d 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -247,8 +247,8 @@ static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 		NULL
 	};
 	static const char *warning = "warning: refname '%.*s' is ambiguous.\n";
-	const char **p, *pathname;
-	char *real_path = NULL;
+	const char **p, *ref;
+	char *real_ref = NULL;
 	int refs_found = 0, am;
 	unsigned long at_time = (unsigned long)-1;
 	unsigned char *this_result;
@@ -276,10 +276,10 @@ static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 
 	for (p = fmt; *p; p++) {
 		this_result = refs_found ? sha1_from_ref : sha1;
-		pathname = resolve_ref(git_path(*p, len, str), this_result, 1);
-		if (pathname) {
+		ref = resolve_ref(mkpath(*p, len, str), this_result, 1);
+		if (ref) {
 			if (!refs_found++)
-				real_path = xstrdup(pathname);
+				real_ref = xstrdup(ref);
 			if (!warn_ambiguous_refs)
 				break;
 		}
@@ -293,12 +293,12 @@ static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 
 	if (at_time != (unsigned long)-1) {
 		read_ref_at(
-			real_path + strlen(git_path(".")) - 1,
+			real_ref,
 			at_time,
 			sha1);
 	}
 
-	free(real_path);
+	free(real_ref);
 	return 0;
 }