Merge branch 'jc/ref-locking' into next

* jc/ref-locking:
  Teach receive-pack about ref-log
  update a few Porcelain-ish for ref lock safety.
  update-ref: -d flag and ref creation safety.
  Clean-up lock-ref implementation

Documentation/git-update-ref.txt

@@ -7,7 +7,7 @@ git-update-ref - update the object name stored in a ref safely
 
 SYNOPSIS
 --------
-'git-update-ref' [-m <reason>] <ref> <newvalue> [<oldvalue>]
+'git-update-ref' [-m <reason>] (-d <ref> <oldvalue> | <ref> <newvalue> [<oldvalue>])
 
 DESCRIPTION
 -----------
@@ -20,7 +20,9 @@ possibly dereferencing the symbolic refs, after verifying that
 the current value of the <ref> matches <oldvalue>.
 E.g. `git-update-ref refs/heads/master <newvalue> <oldvalue>`
 updates the master branch head to <newvalue> only if its current
-value is <oldvalue>.
+value is <oldvalue>.  You can specify 40 "0" or an empty string
+as <oldvalue> to make sure that the ref you are creating does
+not exist.
 
 It also allows a "ref" file to be a symbolic pointer to another
 ref file by starting with the four-byte header sequence of
@@ -49,6 +51,10 @@ for reading but not for writing (so we'll never write through a
 ref symlink to some other tree, if you have copied a whole
 archive by creating a symlink tree).
 
+With `-d` flag, it deletes the named <ref> after verifying it
+still contains <oldvalue>.
+
+
 Logging Updates
 ---------------
 If config parameter "core.logAllRefUpdates" is true or the file

builtin-pack-refs.c

@@ -53,7 +53,7 @@ static int handle_one_ref(const char *path, const unsigned char *sha1,
 /* make sure nobody touched the ref, and unlink */
 static void prune_ref(struct ref_to_prune *r)
 {
-	struct ref_lock *lock = lock_ref_sha1(r->name + 5, r->sha1, 1);
+	struct ref_lock *lock = lock_ref_sha1(r->name + 5, r->sha1);
 
 	if (lock) {
 		unlink(git_path("%s", r->name));

builtin-update-ref.c

@@ -3,15 +3,16 @@
 #include "builtin.h"
 
 static const char git_update_ref_usage[] =
-"git-update-ref <refname> <value> [<oldval>] [-m <reason>]";
+"git-update-ref [-m <reason>] (-d <refname> <value> | <refname> <value> [<oldval>])";
 
 int cmd_update_ref(int argc, const char **argv, const char *prefix)
 {
 	const char *refname=NULL, *value=NULL, *oldval=NULL, *msg=NULL;
 	struct ref_lock *lock;
 	unsigned char sha1[20], oldsha1[20];
-	int i;
+	int i, delete;
 
+	delete = 0;
 	setup_ident();
 	git_config(git_default_config);
 
@@ -26,6 +27,10 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
 				die("Refusing to perform update with \\n in message.");
 			continue;
 		}
+		if (!strcmp("-d", argv[i])) {
+			delete = 1;
+			continue;
+		}
 		if (!refname) {
 			refname = argv[i];
 			continue;
@@ -44,11 +49,18 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
 
 	if (get_sha1(value, sha1))
 		die("%s: not a valid SHA1", value);
+
+	if (delete) {
+		if (oldval)
+			usage(git_update_ref_usage);
+		return delete_ref(refname, sha1);
+	}
+
 	hashclr(oldsha1);
-	if (oldval && get_sha1(oldval, oldsha1))
+	if (oldval && *oldval && get_sha1(oldval, oldsha1))
 		die("%s: not a valid old SHA1", oldval);
 
-	lock = lock_any_ref_for_update(refname, oldval ? oldsha1 : NULL, 0);
+	lock = lock_any_ref_for_update(refname, oldval ? oldsha1 : NULL);
 	if (!lock)
 		return 1;
 	if (write_ref_sha1(lock, sha1, msg) < 0)

cache.h

@@ -179,6 +179,7 @@ struct lock_file {
 extern int hold_lock_file_for_update(struct lock_file *, const char *path, int);
 extern int commit_lock_file(struct lock_file *);
 extern void rollback_lock_file(struct lock_file *);
+extern int delete_ref(const char *, unsigned char *sha1);
 
 /* Environment bits from configuration mechanism */
 extern int use_legacy_headers;

fetch.c

@@ -266,7 +266,7 @@ int pull(int targets, char **target, const char **write_ref,
 		if (!write_ref || !write_ref[i])
 			continue;
 
-		lock[i] = lock_ref_sha1(write_ref[i], NULL, 0);
+		lock[i] = lock_ref_sha1(write_ref[i], NULL);
 		if (!lock[i]) {
 			error("Can't lock ref %s", write_ref[i]);
 			goto unlock_and_fail;

git-branch.sh

@@ -42,8 +42,7 @@ If you are sure you want to delete it, run 'git branch -D $branch_name'."
 	    esac
 	    ;;
 	esac
-	rm -f "$GIT_DIR/logs/refs/heads/$branch_name"
-	rm -f "$GIT_DIR/refs/heads/$branch_name"
+	git update-ref -d "refs/heads/$branch_name" "$branch"
 	echo "Deleted branch $branch_name."
     done
     exit 0
@@ -122,6 +121,7 @@ then
 	done
 fi
 
+prev=''
 if git-show-ref --verify --quiet -- "refs/heads/$branchname"
 then
 	if test '' = "$force"
@@ -131,10 +131,11 @@ then
 	then
 		die "cannot force-update the current branch."
 	fi
+	prev=`git rev-parse --verify "refs/heads/$branchname"`
 fi
 if test "$create_log" = 'yes'
 then
 	mkdir -p $(dirname "$GIT_DIR/logs/refs/heads/$branchname")
 	touch "$GIT_DIR/logs/refs/heads/$branchname"
 fi
-git update-ref -m "branch: Created from $head" "refs/heads/$branchname" $rev
+git update-ref -m "branch: Created from $head" "refs/heads/$branchname" "$rev" "$prev"

git-commit.sh

@@ -547,15 +547,15 @@ then
 		PARENTS=$(git-cat-file commit HEAD |
 			sed -n -e '/^$/q' -e 's/^parent /-p /p')
 	fi
-	current=$(git-rev-parse --verify HEAD)
+	current="$(git-rev-parse --verify HEAD)"
 else
 	if [ -z "$(git-ls-files)" ]; then
 		echo >&2 Nothing to commit
 		exit 1
 	fi
 	PARENTS=""
-	current=
 	rloga='commit (initial)'
+	current=''
 fi
 
 if test -z "$no_edit"
@@ -631,7 +631,7 @@ then
 	fi &&
 	commit=$(cat "$GIT_DIR"/COMMIT_MSG | git-commit-tree $tree $PARENTS) &&
 	rlogm=$(sed -e 1q "$GIT_DIR"/COMMIT_MSG) &&
-	git-update-ref -m "$rloga: $rlogm" HEAD $commit $current &&
+	git-update-ref -m "$rloga: $rlogm" HEAD $commit "$current" &&
 	rm -f -- "$GIT_DIR/MERGE_HEAD" &&
 	if test -f "$NEXT_INDEX"
 	then

git-tag.sh

@@ -63,8 +63,11 @@ done
 
 name="$1"
 [ "$name" ] || usage
-if [ -e "$GIT_DIR/refs/tags/$name" -a -z "$force" ]; then
-    die "tag '$name' already exists"
+prev=0000000000000000000000000000000000000000
+if test -e "$GIT_DIR/refs/tags/$name"
+then
+    test -n "$force" || die "tag '$name' already exists"
+    prev=`git rev-parse "refs/tags/$name"`
 fi
 shift
 git-check-ref-format "tags/$name" ||
@@ -109,4 +112,4 @@ fi
 
 leading=`expr "refs/tags/$name" : '\(.*\)/'` &&
 mkdir -p "$GIT_DIR/$leading" &&
-echo $object > "$GIT_DIR/refs/tags/$name"
+GIT_DIR="$GIT_DIR" git update-ref "refs/tags/$name" "$object" "$prev"

receive-pack.c

@@ -43,34 +43,6 @@ struct command {
 
 static struct command *commands;
 
-static int is_all_zeroes(const char *hex)
-{
-	int i;
-	for (i = 0; i < 40; i++)
-		if (*hex++ != '0')
-			return 0;
-	return 1;
-}
-
-static int verify_old_ref(const char *name, char *hex_contents)
-{
-	int fd, ret;
-	char buffer[60];
-
-	if (is_all_zeroes(hex_contents))
-		return 0;
-	fd = open(name, O_RDONLY);
-	if (fd < 0)
-		return -1;
-	ret = read(fd, buffer, 40);
-	close(fd);
-	if (ret != 40)
-		return -1;
-	if (memcmp(buffer, hex_contents, 40))
-		return -1;
-	return 0;
-}
-
 static char update_hook[] = "hooks/update";
 
 static int run_update_hook(const char *refname,
@@ -107,8 +79,8 @@ static int update(struct command *cmd)
 	const char *name = cmd->ref_name;
 	unsigned char *old_sha1 = cmd->old_sha1;
 	unsigned char *new_sha1 = cmd->new_sha1;
-	char new_hex[60], *old_hex, *lock_name;
-	int newfd, namelen, written;
+	char new_hex[41], old_hex[41];
+	struct ref_lock *lock;
 
 	cmd->error_string = NULL;
 	if (!strncmp(name, "refs/", 5) && check_ref_format(name + 5)) {
@@ -117,13 +89,8 @@ static int update(struct command *cmd)
 			     name);
 	}
 
-	namelen = strlen(name);
-	lock_name = xmalloc(namelen + 10);
-	memcpy(lock_name, name, namelen);
-	memcpy(lock_name + namelen, ".lock", 6);
-
 	strcpy(new_hex, sha1_to_hex(new_sha1));
-	old_hex = sha1_to_hex(old_sha1);
+	strcpy(old_hex, sha1_to_hex(old_sha1));
 	if (!has_sha1_file(new_sha1)) {
 		cmd->error_string = "bad pack";
 		return error("unpack should have generated %s, "
@@ -144,47 +111,20 @@ static int update(struct command *cmd)
 			return error("denying non-fast forward;"
 				     " you should pull first");
 	}
-	safe_create_leading_directories(lock_name);
-
-	newfd = open(lock_name, O_CREAT | O_EXCL | O_WRONLY, 0666);
-	if (newfd < 0) {
-		cmd->error_string = "can't lock";
-		return error("unable to create %s (%s)",
-			     lock_name, strerror(errno));
-	}
-
-	/* Write the ref with an ending '\n' */
-	new_hex[40] = '\n';
-	new_hex[41] = 0;
-	written = write(newfd, new_hex, 41);
-	/* Remove the '\n' again */
-	new_hex[40] = 0;
-
-	close(newfd);
-	if (written != 41) {
-		unlink(lock_name);
-		cmd->error_string = "can't write";
-		return error("unable to write %s", lock_name);
-	}
-	if (verify_old_ref(name, old_hex) < 0) {
-		unlink(lock_name);
-		cmd->error_string = "raced";
-		return error("%s changed during push", name);
-	}
 	if (run_update_hook(name, old_hex, new_hex)) {
-		unlink(lock_name);
 		cmd->error_string = "hook declined";
 		return error("hook declined to update %s", name);
 	}
-	else if (rename(lock_name, name) < 0) {
-		unlink(lock_name);
-		cmd->error_string = "can't rename";
-		return error("unable to replace %s", name);
-	}
-	else {
-		fprintf(stderr, "%s: %s -> %s\n", name, old_hex, new_hex);
-		return 0;
+
+	lock = lock_any_ref_for_update(name, old_sha1);
+	if (!lock) {
+		cmd->error_string = "failed to lock";
+		return error("failed to lock %s", name);
 	}
+	write_ref_sha1(lock, new_sha1, "push");
+
+	fprintf(stderr, "%s: %s -> %s\n", name, old_hex, new_hex);
+	return 0;
 }
 
 static char update_post_hook[] = "hooks/post-update";
@@ -335,9 +275,11 @@ int main(int argc, char **argv)
 	if (!dir)
 		usage(receive_pack_usage);
 
-	if(!enter_repo(dir, 0))
+	if (!enter_repo(dir, 0))
 		die("'%s': unable to chdir or not a git archive", dir);
 
+	git_config(git_default_config);
+
 	write_head_info();
 
 	/* EOF */

refs.c

@@ -378,6 +378,32 @@ int get_ref_sha1(const char *ref, unsigned char *sha1)
 	return read_ref(mkpath("refs/%s", ref), sha1);
 }
 
+int delete_ref(const char *refname, unsigned char *sha1)
+{
+	struct ref_lock *lock;
+	int err, i, ret = 0;
+
+	lock = lock_any_ref_for_update(refname, sha1);
+	if (!lock)
+		return 1;
+	i = strlen(lock->lk->filename) - 5; /* .lock */
+	lock->lk->filename[i] = 0;
+	err = unlink(lock->lk->filename);
+	if (err) {
+		ret = 1;
+		error("unlink(%s) failed: %s",
+		      lock->lk->filename, strerror(errno));
+	}
+	lock->lk->filename[i] = '.';
+
+	err = unlink(lock->log_file);
+	if (err && errno != ENOENT)
+		fprintf(stderr, "warning: unlink(%s) failed: %s",
+			lock->log_file, strerror(errno));
+
+	return ret;
+}
+
 /*
  * Make sure "ref" is something reasonable to have under ".git/refs/";
  * We do not like it if:
@@ -447,12 +473,13 @@ static struct ref_lock *verify_lock(struct ref_lock *lock,
 	return lock;
 }
 
-static struct ref_lock *lock_ref_sha1_basic(const char *ref, const unsigned char *old_sha1, int mustexist)
+static struct ref_lock *lock_ref_sha1_basic(const char *ref, const unsigned char *old_sha1)
 {
 	char *ref_file;
 	const char *orig_ref = ref;
 	struct ref_lock *lock;
 	struct stat st;
+	int mustexist = (old_sha1 && !is_null_sha1(old_sha1));
 
 	lock = xcalloc(1, sizeof(struct ref_lock));
 	lock->lock_fd = -1;
@@ -480,20 +507,18 @@ static struct ref_lock *lock_ref_sha1_basic(const char *ref, const unsigned char
 	return old_sha1 ? verify_lock(lock, old_sha1, mustexist) : lock;
 }
 
-struct ref_lock *lock_ref_sha1(const char *ref,
-	const unsigned char *old_sha1, int mustexist)
+struct ref_lock *lock_ref_sha1(const char *ref, const unsigned char *old_sha1)
 {
 	char refpath[PATH_MAX];
 	if (check_ref_format(ref))
 		return NULL;
 	strcpy(refpath, mkpath("refs/%s", ref));
-	return lock_ref_sha1_basic(refpath, old_sha1, mustexist);
+	return lock_ref_sha1_basic(refpath, old_sha1);
 }
 
-struct ref_lock *lock_any_ref_for_update(const char *ref,
-	const unsigned char *old_sha1, int mustexist)
+struct ref_lock *lock_any_ref_for_update(const char *ref, const unsigned char *old_sha1)
 {
-	return lock_ref_sha1_basic(ref, old_sha1, mustexist);
+	return lock_ref_sha1_basic(ref, old_sha1);
 }
 
 void unlock_ref(struct ref_lock *lock)

refs.h

@@ -27,10 +27,10 @@ extern int for_each_remote_ref(each_ref_fn, void *);
 extern int get_ref_sha1(const char *ref, unsigned char *sha1);
 
 /** Locks a "refs/" ref returning the lock on success and NULL on failure. **/
-extern struct ref_lock *lock_ref_sha1(const char *ref, const unsigned char *old_sha1, int mustexist);
+extern struct ref_lock *lock_ref_sha1(const char *ref, const unsigned char *old_sha1);
 
 /** Locks any ref (for 'HEAD' type refs). */
-extern struct ref_lock *lock_any_ref_for_update(const char *ref, const unsigned char *old_sha1, int mustexist);
+extern struct ref_lock *lock_any_ref_for_update(const char *ref, const unsigned char *old_sha1);
 
 /** Release any lock taken but not written. **/
 extern void unlock_ref(struct ref_lock *lock);