Merge branch 'np/dreflog'

* np/dreflog:
  show-branch -g: default to the current branch.
  Let git-checkout always drop any detached head
  Enable HEAD@{...} and make it independent from the current branch
  scan reflogs independently from refs
  add reflog when moving HEAD to a new branch
  create_symref(): do not assume pathname from git_path() persists long enough
  add logref support to git-symbolic-ref
  move create_symref() past log_ref_write()
  add reflog entries for HEAD when detached
  enable separate reflog for HEAD
  lock_ref_sha1_basic(): remember the original name of a ref when resolving it
  make reflog filename independent from struct ref_lock

14 files changed, 232 insertions, 135 deletions

diff --git a/Documentation/git-show-branch.txt b/Documentation/git-show-branch.txt
index b38633c..ba5313d 100644
--- a/Documentation/git-show-branch.txt
+++ b/Documentation/git-show-branch.txt
@@ -11,7 +11,7 @@ SYNOPSIS
 'git-show-branch' [--all] [--remotes] [--topo-order] [--current]
 		[--more=<n> | --list | --independent | --merge-base]
 		[--no-name | --sha1-name] [--topics] [<rev> | <glob>]...
-'git-show-branch' (-g|--reflog)[=<n>[,<base>]] [--list] <ref>
+'git-show-branch' (-g|--reflog)[=<n>[,<base>]] [--list] [<ref>]
 
 DESCRIPTION
 -----------
@@ -97,11 +97,13 @@ OPTIONS
 	will show the revisions given by "git rev-list {caret}master
 	topic1 topic2"
 
---reflog[=<n>[,<base>]] <ref>::
+--reflog[=<n>[,<base>]] [<ref>]::
 	Shows <n> most recent ref-log entries for the given
 	ref.  If <base> is given, <n> entries going back from
 	that entry.  <base> can be specified as count or date.
-	`-g` can be used as a short-hand for this option.
+	`-g` can be used as a short-hand for this option.  When
+	no explicit <ref> parameter is given, it defaults to the
+	current branch (or `HEAD` if it is detached).
 
 Note that --more, --list, --independent and --merge-base options
 are mutually exclusive.
diff --git a/Documentation/git-symbolic-ref.txt b/Documentation/git-symbolic-ref.txt
index f93b79a..a88f722 100644
--- a/Documentation/git-symbolic-ref.txt
+++ b/Documentation/git-symbolic-ref.txt
@@ -7,7 +7,7 @@ git-symbolic-ref - Read and modify symbolic refs
 
 SYNOPSIS
 --------
-'git-symbolic-ref' [-q] <name> [<ref>]
+'git-symbolic-ref' [-q] [-m <reason>] <name> [<ref>]
 
 DESCRIPTION
 -----------
@@ -31,6 +31,10 @@ OPTIONS
 	symbolic ref but a detached HEAD; instead exit with
 	non-zero status silently.
 
+-m::
+	Update the reflog for <name> with <reason>.  This is valid only
+	when creating or updating a symbolic ref.
+
 NOTES
 -----
 In the past, `.git/HEAD` was a symbolic link pointing at
diff --git a/builtin-branch.c b/builtin-branch.c
index 9b68d3b..2d8d61b 100644
--- a/builtin-branch.c
+++ b/builtin-branch.c
@@ -387,7 +387,8 @@ static void rename_branch(const char *oldname, const char *newname, int force)
 	if (rename_ref(oldref, newref, logmsg))
 		die("Branch rename failed");
 
-	if (!strcmp(oldname, head) && create_symref("HEAD", newref))
+	/* no need to pass logmsg here as HEAD didn't really move */
+	if (!strcmp(oldname, head) && create_symref("HEAD", newref, NULL))
 		die("Branch renamed to %s, but HEAD is not updated!", newname);
 }
 
diff --git a/builtin-fsck.c b/builtin-fsck.c
index f6f1967..6da3814 100644
--- a/builtin-fsck.c
+++ b/builtin-fsck.c
@@ -477,6 +477,12 @@ static int fsck_handle_reflog_ent(unsigned char *osha1, unsigned char *nsha1,
 	return 0;
 }
 
+static int fsck_handle_reflog(const char *logname, const unsigned char *sha1, int flag, void *cb_data)
+{
+	for_each_reflog_ent(logname, fsck_handle_reflog_ent, NULL);
+	return 0;
+}
+
 static int fsck_handle_ref(const char *refname, const unsigned char *sha1, int flag, void *cb_data)
 {
 	struct object *obj;
@@ -495,14 +501,13 @@ static int fsck_handle_ref(const char *refname, const unsigned char *sha1, int f
 	obj->used = 1;
 	mark_reachable(obj, REACHABLE);
 
-	for_each_reflog_ent(refname, fsck_handle_reflog_ent, NULL);
-
 	return 0;
 }
 
 static void get_default_heads(void)
 {
 	for_each_ref(fsck_handle_ref, NULL);
+	for_each_reflog(fsck_handle_reflog, NULL);
 
 	/*
 	 * Not having any default heads isn't really fatal, but
diff --git a/builtin-init-db.c b/builtin-init-db.c
index 1865489..12e43d0 100644
--- a/builtin-init-db.c
+++ b/builtin-init-db.c
@@ -231,7 +231,7 @@ static int create_default_files(const char *git_dir, const char *template_path)
 	strcpy(path + len, "HEAD");
 	reinit = !read_ref("HEAD", sha1);
 	if (!reinit) {
-		if (create_symref("HEAD", "refs/heads/master") < 0)
+		if (create_symref("HEAD", "refs/heads/master", NULL) < 0)
 			exit(1);
 	}
 
diff --git a/builtin-reflog.c b/builtin-reflog.c
index b443ed9..bfb169a 100644
--- a/builtin-reflog.c
+++ b/builtin-reflog.c
@@ -242,20 +242,18 @@ static int expire_reflog(const char *ref, const unsigned char *sha1, int unused,
 	struct cmd_reflog_expire_cb *cmd = cb_data;
 	struct expire_reflog_cb cb;
 	struct ref_lock *lock;
-	char *newlog_path = NULL;
+	char *log_file, *newlog_path = NULL;
 	int status = 0;
 
-	if (strncmp(ref, "refs/", 5))
-		return error("not a ref '%s'", ref);
-
 	memset(&cb, 0, sizeof(cb));
 	/* we take the lock for the ref itself to prevent it from
 	 * getting updated.
 	 */
-	lock = lock_ref_sha1(ref + 5, sha1);
+	lock = lock_any_ref_for_update(ref, sha1);
 	if (!lock)
 		return error("cannot lock ref '%s'", ref);
-	if (!file_exists(lock->log_file))
+	log_file = xstrdup(git_path("logs/%s", ref));
+	if (!file_exists(log_file))
 		goto finish;
 	if (!cmd->dry_run) {
 		newlog_path = xstrdup(git_path("logs/%s.lock", ref));
@@ -271,13 +269,14 @@ static int expire_reflog(const char *ref, const unsigned char *sha1, int unused,
 		if (fclose(cb.newlog))
 			status |= error("%s: %s", strerror(errno),
 					newlog_path);
-		if (rename(newlog_path, lock->log_file)) {
+		if (rename(newlog_path, log_file)) {
 			status |= error("cannot rename %s to %s",
-					newlog_path, lock->log_file);
+					newlog_path, log_file);
 			unlink(newlog_path);
 		}
 	}
 	free(newlog_path);
+	free(log_file);
 	unlock_ref(lock);
 	return status;
 }
@@ -351,7 +350,7 @@ static int cmd_reflog_expire(int argc, const char **argv, const char *prefix)
 	}
 
 	if (do_all)
-		status |= for_each_ref(expire_reflog, &cb);
+		status |= for_each_reflog(expire_reflog, &cb);
 	while (i < argc) {
 		const char *ref = argv[i++];
 		unsigned char sha1[20];
diff --git a/builtin-show-branch.c b/builtin-show-branch.c
index fa62e48..0d94e40 100644
--- a/builtin-show-branch.c
+++ b/builtin-show-branch.c
@@ -690,7 +690,10 @@ int cmd_show_branch(int ac, const char **av, const char *prefix)
 
 		if (ac == 0) {
 			static const char *fake_av[2];
-			fake_av[0] = "HEAD";
+			const char *refname;
+
+			refname = resolve_ref("HEAD", sha1, 1, NULL);
+			fake_av[0] = xstrdup(refname);
 			fake_av[1] = NULL;
 			av = fake_av;
 			ac = 1;
diff --git a/builtin-symbolic-ref.c b/builtin-symbolic-ref.c
index 227c9d4..d41b406 100644
--- a/builtin-symbolic-ref.c
+++ b/builtin-symbolic-ref.c
@@ -3,7 +3,7 @@
 #include "refs.h"
 
 static const char git_symbolic_ref_usage[] =
-"git-symbolic-ref [-q] name [ref]";
+"git-symbolic-ref [-q] [-m <reason>] name [ref]";
 
 static void check_symref(const char *HEAD, int quiet)
 {
@@ -25,6 +25,7 @@ static void check_symref(const char *HEAD, int quiet)
 int cmd_symbolic_ref(int argc, const char **argv, const char *prefix)
 {
 	int quiet = 0;
+	const char *msg = NULL;
 
 	git_config(git_default_config);
 
@@ -34,6 +35,17 @@ int cmd_symbolic_ref(int argc, const char **argv, const char *prefix)
 			break;
 		else if (!strcmp("-q", arg))
 			quiet = 1;
+		else if (!strcmp("-m", arg)) {
+			argc--;
+			argv++;
+			if (argc <= 1)
+				break;
+			msg = argv[1];
+			if (!*msg)
+				die("Refusing to perform update with empty message");
+			if (strchr(msg, '\n'))
+				die("Refusing to perform update with \\n in message");
+		}
 		else if (!strcmp("--", arg)) {
 			argc--;
 			argv++;
@@ -50,7 +62,7 @@ int cmd_symbolic_ref(int argc, const char **argv, const char *prefix)
 		check_symref(argv[1], quiet);
 		break;
 	case 3:
-		create_symref(argv[1], argv[2]);
+		create_symref(argv[1], argv[2], msg);
 		break;
 	default:
 		usage(git_symbolic_ref_usage);
diff --git a/cache.h b/cache.h
index 9873ee9..201704b 100644
--- a/cache.h
+++ b/cache.h
@@ -302,7 +302,7 @@ extern int read_ref(const char *filename, unsigned char *sha1);
 extern const char *resolve_ref(const char *path, unsigned char *sha1, int, int *);
 extern int dwim_ref(const char *str, int len, unsigned char *sha1, char **ref);
 
-extern int create_symref(const char *ref, const char *refs_heads_master);
+extern int create_symref(const char *ref, const char *refs_heads_master, const char *logmsg);
 extern int validate_headref(const char *ref);
 
 extern int base_name_compare(const char *name1, int len1, int mode1, const char *name2, int len2, int mode2);
diff --git a/git-checkout.sh b/git-checkout.sh
index 99a81f5..14835a4 100755
--- a/git-checkout.sh
+++ b/git-checkout.sh
@@ -164,22 +164,9 @@ If you want to create a new branch from this checkout, you may do so
 (now or later) by using -b with the checkout command again. Example:
   git checkout -b <new_branch_name>"
 	fi
-elif test -z "$oldbranch" && test -n "$branch"
+elif test -z "$oldbranch" && test -z "$quiet"
 then
-	# Coming back...
-	if test -z "$force"
-	then
-		git show-ref -d -s | grep "$old" >/dev/null || {
-			echo >&2 \
-"You are not on any branch and switching to branch '$new_name'
-may lose your changes.  At this point, you can do one of two things:
- (1) Decide it is Ok and say 'git checkout -f $new_name';
- (2) Start a new branch from the current commit, by saying
-     'git checkout -b <branch-name>'.
-Leaving your HEAD detached; not switching to branch '$new_name'."
-			exit 1;
-		}
-	fi
+	echo >&2 "Previous HEAD position was $old"
 fi
 
 if [ "X$old" = X ]
@@ -257,7 +244,7 @@ if [ "$?" -eq 0 ]; then
 	fi
 	if test -n "$branch"
 	then
-		GIT_DIR="$GIT_DIR" git-symbolic-ref HEAD "refs/heads/$branch"
+		GIT_DIR="$GIT_DIR" git-symbolic-ref -m "checkout: moving to $branch" HEAD "refs/heads/$branch"
 		if test -z "$quiet"
 		then
 			echo >&2 "Switched to${newbranch:+ a new} branch \"$branch\""
@@ -270,8 +257,9 @@ if [ "$?" -eq 0 ]; then
 		#	git update-ref --detach HEAD $new
 		# or something like that...
 		#
-		echo "$detached" >"$GIT_DIR/HEAD.new" &&
-		mv "$GIT_DIR/HEAD.new" "$GIT_DIR/HEAD" ||
+		git-rev-parse HEAD >"$GIT_DIR/HEAD.new" &&
+		mv "$GIT_DIR/HEAD.new" "$GIT_DIR/HEAD" &&
+		git-update-ref -m "checkout: moving to $arg" HEAD "$detached" ||
 			die "Cannot detach HEAD"
 		if test -n "$detach_warn"
 		then
diff --git a/reachable.c b/reachable.c
index a6a3348..01760d7 100644
--- a/reachable.c
+++ b/reachable.c
@@ -188,9 +188,9 @@ void mark_reachable_objects(struct rev_info *revs, int mark_reflog)
 	/* Add all external refs */
 	for_each_ref(add_one_ref, revs);
 
-	/* Add all reflog info from refs */
+	/* Add all reflog info */
 	if (mark_reflog)
-		for_each_ref(add_one_reflog, revs);
+		for_each_reflog(add_one_reflog, revs);
 
 	/*
 	 * Set up the revision walk - this will move all commits
diff --git a/refs.c b/refs.c
index 3db444c..03e8dfe 100644
--- a/refs.c
+++ b/refs.c
@@ -309,53 +309,6 @@ const char *resolve_ref(const char *ref, unsigned char *sha1, int reading, int *
 	return ref;
 }
 
-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) {
-		unlink(git_HEAD);
-		if (!symlink(refs_heads_master, git_HEAD))
-			return 0;
-		fprintf(stderr, "no symlink - falling back to symbolic ref\n");
-	}
-#endif
-
-	len = snprintf(ref, sizeof(ref), "ref: %s\n", refs_heads_master);
-	if (sizeof(ref) <= len) {
-		error("refname too long: %s", refs_heads_master);
-		return -1;
-	}
-	lockpath = mkpath("%s.lock", git_HEAD);
-	fd = open(lockpath, O_CREAT | O_EXCL | O_WRONLY, 0666);
-	if (fd < 0) {
-		error("Unable to open %s for writing", lockpath);
-		return -5;
-	}
-	written = write_in_full(fd, ref, len);
-	close(fd);
-	if (written != len) {
-		unlink(lockpath);
-		error("Unable to write to %s", lockpath);
-		return -2;
-	}
-	if (rename(lockpath, git_HEAD) < 0) {
-		unlink(lockpath);
-		error("Unable to create %s", git_HEAD);
-		return -3;
-	}
-	if (adjust_shared_perm(git_HEAD)) {
-		unlink(lockpath);
-		error("Unable to fix permissions on %s", lockpath);
-		return -4;
-	}
-	return 0;
-}
-
 int read_ref(const char *ref, unsigned char *sha1)
 {
 	if (resolve_ref(ref, sha1, 1, NULL))
@@ -680,7 +633,7 @@ static struct ref_lock *lock_ref_sha1_basic(const char *ref, const unsigned char
 	lock->lk = xcalloc(1, sizeof(struct lock_file));
 
 	lock->ref_name = xstrdup(ref);
-	lock->log_file = xstrdup(git_path("logs/%s", ref));
+	lock->orig_ref_name = xstrdup(orig_ref);
 	ref_file = git_path("%s", ref);
 	lock->force_write = lstat(ref_file, &st) && errno == ENOENT;
 
@@ -778,10 +731,10 @@ int delete_ref(const char *refname, unsigned char *sha1)
 	 */
 	ret |= repack_without_ref(refname);
 
-	err = unlink(lock->log_file);
+	err = unlink(git_path("logs/%s", lock->ref_name));
 	if (err && errno != ENOENT)
 		fprintf(stderr, "warning: unlink(%s) failed: %s",
-			lock->log_file, strerror(errno));
+			git_path("logs/%s", lock->ref_name), strerror(errno));
 	invalidate_cached_refs();
 	unlock_ref(lock);
 	return ret;
@@ -922,47 +875,50 @@ void unlock_ref(struct ref_lock *lock)
 			rollback_lock_file(lock->lk);
 	}
 	free(lock->ref_name);
-	free(lock->log_file);
+	free(lock->orig_ref_name);
 	free(lock);
 }
 
-static int log_ref_write(struct ref_lock *lock,
-	const unsigned char *sha1, const char *msg)
+static int log_ref_write(const char *ref_name, const unsigned char *old_sha1,
+			 const unsigned char *new_sha1, const char *msg)
 {
 	int logfd, written, oflags = O_APPEND | O_WRONLY;
 	unsigned maxlen, len;
 	int msglen;
-	char *logrec;
+	char *log_file, *logrec;
 	const char *committer;
 
 	if (log_all_ref_updates < 0)
 		log_all_ref_updates = !is_bare_repository();
 
+	log_file = git_path("logs/%s", ref_name);
+
 	if (log_all_ref_updates &&
-	    (!strncmp(lock->ref_name, "refs/heads/", 11) ||
-	     !strncmp(lock->ref_name, "refs/remotes/", 13))) {
-		if (safe_create_leading_directories(lock->log_file) < 0)
+	    (!strncmp(ref_name, "refs/heads/", 11) ||
+	     !strncmp(ref_name, "refs/remotes/", 13) ||
+	     !strcmp(ref_name, "HEAD"))) {
+		if (safe_create_leading_directories(log_file) < 0)
 			return error("unable to create directory for %s",
-				lock->log_file);
+				     log_file);
 		oflags |= O_CREAT;
 	}
 
-	logfd = open(lock->log_file, oflags, 0666);
+	logfd = open(log_file, oflags, 0666);
 	if (logfd < 0) {
 		if (!(oflags & O_CREAT) && errno == ENOENT)
 			return 0;
 
 		if ((oflags & O_CREAT) && errno == EISDIR) {
-			if (remove_empty_directories(lock->log_file)) {
+			if (remove_empty_directories(log_file)) {
 				return error("There are still logs under '%s'",
-					     lock->log_file);
+					     log_file);
 			}
-			logfd = open(lock->log_file, oflags, 0666);
+			logfd = open(log_file, oflags, 0666);
 		}
 
 		if (logfd < 0)
 			return error("Unable to append to %s: %s",
-				     lock->log_file, strerror(errno));
+				     log_file, strerror(errno));
 	}
 
 	msglen = 0;
@@ -984,8 +940,8 @@ static int log_ref_write(struct ref_lock *lock,
 	maxlen = strlen(committer) + msglen + 100;
 	logrec = xmalloc(maxlen);
 	len = sprintf(logrec, "%s %s %s\n",
-		      sha1_to_hex(lock->old_sha1),
-		      sha1_to_hex(sha1),
+		      sha1_to_hex(old_sha1),
+		      sha1_to_hex(new_sha1),
 		      committer);
 	if (msglen)
 		len += sprintf(logrec + len - 1, "\t%.*s\n", msglen, msg) - 1;
@@ -993,7 +949,7 @@ static int log_ref_write(struct ref_lock *lock,
 	free(logrec);
 	close(logfd);
 	if (written != len)
-		return error("Unable to append to %s", lock->log_file);
+		return error("Unable to append to %s", log_file);
 	return 0;
 }
 
@@ -1016,7 +972,9 @@ int write_ref_sha1(struct ref_lock *lock,
 		return -1;
 	}
 	invalidate_cached_refs();
-	if (log_ref_write(lock, sha1, logmsg) < 0) {
+	if (log_ref_write(lock->ref_name, lock->old_sha1, sha1, logmsg) < 0 ||
+	    (strcmp(lock->ref_name, lock->orig_ref_name) &&
+	     log_ref_write(lock->orig_ref_name, lock->old_sha1, sha1, logmsg) < 0)) {
 		unlock_ref(lock);
 		return -1;
 	}
@@ -1030,6 +988,65 @@ int write_ref_sha1(struct ref_lock *lock,
 	return 0;
 }
 
+int create_symref(const char *ref_target, const char *refs_heads_master,
+		  const char *logmsg)
+{
+	const char *lockpath;
+	char ref[1000];
+	int fd, len, written;
+	char *git_HEAD = xstrdup(git_path("%s", ref_target));
+	unsigned char old_sha1[20], new_sha1[20];
+
+	if (logmsg && read_ref(ref_target, old_sha1))
+		hashclr(old_sha1);
+
+#ifndef NO_SYMLINK_HEAD
+	if (prefer_symlink_refs) {
+		unlink(git_HEAD);
+		if (!symlink(refs_heads_master, git_HEAD))
+			goto done;
+		fprintf(stderr, "no symlink - falling back to symbolic ref\n");
+	}
+#endif
+
+	len = snprintf(ref, sizeof(ref), "ref: %s\n", refs_heads_master);
+	if (sizeof(ref) <= len) {
+		error("refname too long: %s", refs_heads_master);
+		goto error_free_return;
+	}
+	lockpath = mkpath("%s.lock", git_HEAD);
+	fd = open(lockpath, O_CREAT | O_EXCL | O_WRONLY, 0666);
+	if (fd < 0) {
+		error("Unable to open %s for writing", lockpath);
+		goto error_free_return;
+	}
+	written = write_in_full(fd, ref, len);
+	close(fd);
+	if (written != len) {
+		error("Unable to write to %s", lockpath);
+		goto error_unlink_return;
+	}
+	if (rename(lockpath, git_HEAD) < 0) {
+		error("Unable to create %s", git_HEAD);
+		goto error_unlink_return;
+	}
+	if (adjust_shared_perm(git_HEAD)) {
+		error("Unable to fix permissions on %s", lockpath);
+	error_unlink_return:
+		unlink(lockpath);
+	error_free_return:
+		free(git_HEAD);
+		return -1;
+	}
+
+	done:
+	if (logmsg && !read_ref(refs_heads_master, new_sha1))
+		log_ref_write(ref_target, old_sha1, new_sha1, logmsg);
+
+	free(git_HEAD);
+	return 0;
+}
+
 static char *ref_msg(const char *line, const char *endp)
 {
 	const char *ep;
@@ -1186,3 +1203,53 @@ int for_each_reflog_ent(const char *ref, each_reflog_ent_fn fn, void *cb_data)
 	return ret;
 }
 
+static int do_for_each_reflog(const char *base, each_ref_fn fn, void *cb_data)
+{
+	DIR *dir = opendir(git_path("logs/%s", base));
+	int retval = errno;
+
+	if (dir) {
+		struct dirent *de;
+		int baselen = strlen(base);
+		char *log = xmalloc(baselen + 257);
+
+		memcpy(log, base, baselen);
+		if (baselen && base[baselen-1] != '/')
+			log[baselen++] = '/';
+
+		while ((de = readdir(dir)) != NULL) {
+			struct stat st;
+			int namelen;
+
+			if (de->d_name[0] == '.')
+				continue;
+			namelen = strlen(de->d_name);
+			if (namelen > 255)
+				continue;
+			if (has_extension(de->d_name, ".lock"))
+				continue;
+			memcpy(log + baselen, de->d_name, namelen+1);
+			if (stat(git_path("logs/%s", log), &st) < 0)
+				continue;
+			if (S_ISDIR(st.st_mode)) {
+				retval = do_for_each_reflog(log, fn, cb_data);
+			} else {
+				unsigned char sha1[20];
+				if (!resolve_ref(log, sha1, 0, NULL))
+					retval = error("bad ref for %s", log);
+				else
+					retval = fn(log, sha1, 0, cb_data);
+			}
+			if (retval)
+				break;
+		}
+		free(log);
+		closedir(dir);
+	}
+	return retval;
+}
+
+int for_each_reflog(each_ref_fn fn, void *cb_data)
+{
+	return do_for_each_reflog("", fn, cb_data);
+}
diff --git a/refs.h b/refs.h
index 33450f1..acedffc 100644
--- a/refs.h
+++ b/refs.h
@@ -3,7 +3,7 @@
 
 struct ref_lock {
 	char *ref_name;
-	char *log_file;
+	char *orig_ref_name;
 	struct lock_file *lk;
 	unsigned char old_sha1[20];
 	int lock_fd;
@@ -48,6 +48,12 @@ extern int read_ref_at(const char *ref, unsigned long at_time, int cnt, unsigned
 typedef int each_reflog_ent_fn(unsigned char *osha1, unsigned char *nsha1, const char *, unsigned long, int, const char *, void *);
 int for_each_reflog_ent(const char *ref, each_reflog_ent_fn fn, void *cb_data);
 
+/*
+ * Calls the specified function for each reflog file until it returns nonzero,
+ * and returns the value
+ */
+extern int for_each_reflog(each_ref_fn, void *);
+
 /** Returns 0 if target has the right format for a ref. **/
 extern int check_ref_format(const char *target);
 
diff --git a/sha1_name.c b/sha1_name.c
index de8caf8..d77f770 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -235,22 +235,23 @@ static int ambiguous_path(const char *path, int len)
 	return slash;
 }
 
+static const char *ref_fmt[] = {
+	"%.*s",
+	"refs/%.*s",
+	"refs/tags/%.*s",
+	"refs/heads/%.*s",
+	"refs/remotes/%.*s",
+	"refs/remotes/%.*s/HEAD",
+	NULL
+};
+
 int dwim_ref(const char *str, int len, unsigned char *sha1, char **ref)
 {
-	static const char *fmt[] = {
-		"%.*s",
-		"refs/%.*s",
-		"refs/tags/%.*s",
-		"refs/heads/%.*s",
-		"refs/remotes/%.*s",
-		"refs/remotes/%.*s/HEAD",
-		NULL
-	};
 	const char **p, *r;
 	int refs_found = 0;
 
 	*ref = NULL;
-	for (p = fmt; *p; p++) {
+	for (p = ref_fmt; *p; p++) {
 		unsigned char sha1_from_ref[20];
 		unsigned char *this_result;
 
@@ -266,6 +267,28 @@ int dwim_ref(const char *str, int len, unsigned char *sha1, char **ref)
 	return refs_found;
 }
 
+static int dwim_log(const char *str, int len, unsigned char *sha1, char **log)
+{
+	const char **p;
+	int logs_found = 0;
+
+	*log = NULL;
+	for (p = ref_fmt; *p; p++) {
+		struct stat st;
+		char *path = mkpath(*p, len, str);
+		if (!stat(git_path("logs/%s", path), &st) &&
+		    S_ISREG(st.st_mode)) {
+			if (!logs_found++) {
+				*log = xstrdup(path);
+				resolve_ref(path, sha1, 0, NULL);
+			}
+			if (!warn_ambiguous_refs)
+				break;
+		}
+	}
+	return logs_found;
+}
+
 static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 {
 	static const char *warning = "warning: refname '%.*s' is ambiguous.\n";
@@ -295,7 +318,9 @@ static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 	if (!len && reflog_len) {
 		/* allow "@{...}" to mean the current branch reflog */
 		refs_found = dwim_ref("HEAD", 4, sha1, &real_ref);
-	} else
+	} else if (reflog_len)
+		refs_found = dwim_log(str, len, sha1, &real_ref);
+	else
 		refs_found = dwim_ref(str, len, sha1, &real_ref);
 
 	if (!refs_found)
@@ -310,21 +335,6 @@ static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 		unsigned long co_time;
 		int co_tz, co_cnt;
 
-		/*
-		 * We'll have an independent reflog for "HEAD" eventually
-		 * which won't be a synonym for the current branch reflog.
-		 * In the mean time prevent people from getting used to
-		 * such a synonym until the work is completed.
-		 */
-		if (len && !strncmp("HEAD", str, len) &&
-		    !strncmp(real_ref, "refs/", 5)) {
-			error("reflog for HEAD has not been implemented yet\n"
-			      "Maybe you could try %s%s instead, "
-			      "or just %s for current branch..",
-			      strchr(real_ref+5, '/')+1, str+len, str+len);
-			exit(-1);
-		}
-
 		/* Is it asking for N-th entry, or approxidate? */
 		for (i = nth = 0; 0 <= nth && i < reflog_len; i++) {
 			char ch = str[at+2+i];