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

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.

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

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);
 }
 

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

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);
 	}
 

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];

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;

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);

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);

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

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