Merge branch 'jc/lt-ref2-with-lt-refs' into jc/ref-locking

* jc/lt-ref2-with-lt-refs:
  Fix show-ref usage for --dereference.
  Document git-show-ref [-s|--hash] option.
  Add man page for git-show-ref
  gitignore: git-show-ref is a generated file.
  Use Linus' show ref in "git-branch.sh".
  Add [-s|--hash] option to Linus' show-ref.
  Teach "git checkout" to use git-show-ref
  Add "git show-ref" builtin command

8 files changed, 281 insertions, 4 deletions

diff --git a/.gitignore b/.gitignore
index 688a502d9..0ffe14ac4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -106,6 +106,7 @@ git-shortlog
 git-show
 git-show-branch
 git-show-index
+git-show-ref
 git-ssh-fetch
 git-ssh-pull
 git-ssh-push
diff --git a/Documentation/git-show-ref.txt b/Documentation/git-show-ref.txt
new file mode 100644
index 000000000..b724d832c
--- /dev/null
+++ b/Documentation/git-show-ref.txt
@@ -0,0 +1,152 @@
+git-show-ref(1)
+===============
+
+NAME
+----
+git-show-ref - List references in a local repository
+
+SYNOPSIS
+--------
+[verse]
+'git-show-ref' [-q|--quiet] [--verify] [-h|--head] [-d|--dereference]
+	     [-s|--hash] [--tags] [--heads] [--] <pattern>...
+
+DESCRIPTION
+-----------
+
+Displays references available in a local repository along with the associated
+commit IDs. Results can be filtered using a pattern and tags can be
+dereferenced into object IDs. Additionally, it can be used to test whether a
+particular ref exists.
+
+Use of this utility is encouraged in favor of directly accessing files under
+in the `.git` directory.
+
+OPTIONS
+-------
+
+-h, --head::
+
+	Show the HEAD reference.
+
+--tags, --heads::
+
+	Limit to only "refs/heads" and "refs/tags", respectively.  These
+	options are not mutually exclusive; when given both, references stored
+	in "refs/heads" and "refs/tags" are displayed.
+
+-d, --dereference::
+
+	Dereference tags into object IDs. They will be shown with "^{}"
+	appended.
+
+-s, --hash::
+
+	Only show the SHA1 hash, not the reference name. When also using
+	--dereference the dereferenced tag will still be shown after the SHA1,
+	this maybe a bug.
+
+--verify::
+
+	Enable stricter reference checking by requiring an exact ref path.
+	Aside from returning an error code of 1, it will also print an error
+	message if '--quiet' was not specified.
+
+-q, --quiet::
+
+	Do not print any results to stdout. When combined with '--verify' this
+	can be used to silently check if a reference exists.
+
+<pattern>::
+
+	Show references matching one or more patterns.
+
+OUTPUT
+------
+
+The output is in the format: '<SHA-1 ID>' '<space>' '<reference name>'.
+
+-----------------------------------------------------------------------------
+$ git show-ref --head --dereference
+832e76a9899f560a90ffd62ae2ce83bbeff58f54 HEAD
+832e76a9899f560a90ffd62ae2ce83bbeff58f54 refs/heads/master
+832e76a9899f560a90ffd62ae2ce83bbeff58f54 refs/heads/origin
+3521017556c5de4159da4615a39fa4d5d2c279b5 refs/tags/v0.99.9c
+6ddc0964034342519a87fe013781abf31c6db6ad refs/tags/v0.99.9c^{}
+055e4ae3ae6eb344cbabf2a5256a49ea66040131 refs/tags/v1.0rc4
+423325a2d24638ddcc82ce47be5e40be550f4507 refs/tags/v1.0rc4^{}
+...
+-----------------------------------------------------------------------------
+
+When using --hash (and not --dereference) the output format is: '<SHA-1 ID>'
+
+-----------------------------------------------------------------------------
+$ git show-ref --heads --hash
+2e3ba0114a1f52b47df29743d6915d056be13278
+185008ae97960c8d551adcd9e23565194651b5d1
+03adf42c988195b50e1a1935ba5fcbc39b2b029b
+...
+-----------------------------------------------------------------------------
+
+EXAMPLE
+-------
+
+To show all references called "master", whether tags or heads or anything
+else, and regardless of how deep in the reference naming hierarchy they are,
+use:
+
+-----------------------------------------------------------------------------
+	git show-ref master
+-----------------------------------------------------------------------------
+
+This will show "refs/heads/master" but also "refs/remote/other-repo/master",
+if such references exists.
+
+When using the '--verify' flag, the command requires an exact path:
+
+-----------------------------------------------------------------------------
+	git show-ref --verify refs/heads/master
+-----------------------------------------------------------------------------
+
+will only match the exact branch called "master".
+
+If nothing matches, gitlink:git-show-ref[1] will return an error code of 1,
+and in the case of verification, it will show an error message.
+
+For scripting, you can ask it to be quiet with the "--quiet" flag, which
+allows you to do things like
+
+-----------------------------------------------------------------------------
+	git-show-ref --quiet --verify -- "refs/heads/$headname" ||
+		echo "$headname is not a valid branch"
+-----------------------------------------------------------------------------
+
+to check whether a particular branch exists or not (notice how we don't
+actually want to show any results, and we want to use the full refname for it
+in order to not trigger the problem with ambiguous partial matches).
+
+To show only tags, or only proper branch heads, use "--tags" and/or "--heads"
+respectively (using both means that it shows tags and heads, but not other
+random references under the refs/ subdirectory).
+
+To do automatic tag object dereferencing, use the "-d" or "--dereference"
+flag, so you can do
+
+-----------------------------------------------------------------------------
+	git show-ref --tags --dereference
+-----------------------------------------------------------------------------
+
+to get a listing of all tags together with what they dereference.
+
+SEE ALSO
+--------
+gitlink:git-ls-remote[1], gitlink:git-peek-remote[1]
+
+AUTHORS
+-------
+Written by Linus Torvalds <torvalds@osdl.org>.
+Man page by Jonas Fonseca <fonseca@diku.dk>.
+
+GIT
+---
+Part of the gitlink:git[7] suite
diff --git a/Makefile b/Makefile
index 54ac74e98..af4d68fd7 100644
--- a/Makefile
+++ b/Makefile
@@ -303,6 +303,7 @@ BUILTIN_OBJS = \
 	builtin-verify-pack.o \
 	builtin-write-tree.o \
 	builtin-zip-tree.o \
+	builtin-show-ref.o \
 	builtin-pack-refs.o
 
 GITLIBS = $(LIB_FILE) $(XDIFF_LIB)
diff --git a/builtin-show-ref.c b/builtin-show-ref.c
new file mode 100644
index 000000000..12c457c3c
--- /dev/null
+++ b/builtin-show-ref.c
@@ -0,0 +1,120 @@
+#include "cache.h"
+#include "refs.h"
+#include "object.h"
+#include "tag.h"
+
+static const char show_ref_usage[] = "git show-ref [-q|--quiet] [--verify] [-h|--head] [-d|--dereference] [-s|--hash] [--tags] [--heads] [--] [pattern*]";
+
+static int deref_tags = 0, show_head = 0, tags_only = 0, heads_only = 0,
+	found_match = 0, verify = 0, quiet = 0, hash_only = 0;
+static const char **pattern;
+
+static int show_ref(const char *refname, const unsigned char *sha1, int flag, void *cbdata)
+{
+	struct object *obj;
+
+	if (tags_only || heads_only) {
+		int match;
+
+		match = heads_only && !strncmp(refname, "refs/heads/", 11);
+		match |= tags_only && !strncmp(refname, "refs/tags/", 10);
+		if (!match)
+			return 0;
+	}
+	if (pattern) {
+		int reflen = strlen(refname);
+		const char **p = pattern, *m;
+		while ((m = *p++) != NULL) {
+			int len = strlen(m);
+			if (len > reflen)
+				continue;
+			if (memcmp(m, refname + reflen - len, len))
+				continue;
+			if (len == reflen)
+				goto match;
+			/* "--verify" requires an exact match */
+			if (verify)
+				continue;
+			if (refname[reflen - len - 1] == '/')
+				goto match;
+		}
+		return 0;
+	}
+
+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));
+	}
+	if (quiet)
+		return 0;
+	if (hash_only)
+		printf("%s\n", sha1_to_hex(sha1));
+	else
+		printf("%s %s\n", sha1_to_hex(sha1), refname);
+	if (deref_tags && obj->type == OBJ_TAG) {
+		obj = deref_tag(obj, refname, 0);
+		printf("%s %s^{}\n", sha1_to_hex(obj->sha1), refname);
+	}
+	return 0;
+}
+
+int cmd_show_ref(int argc, const char **argv, const char *prefix)
+{
+	int i;
+
+	for (i = 1; i < argc; i++) {
+		const char *arg = argv[i];
+		if (*arg != '-') {
+			pattern = argv + i;
+			break;
+		}
+		if (!strcmp(arg, "--")) {
+			pattern = argv + i + 1;
+			if (!*pattern)
+				pattern = NULL;
+			break;
+		}
+		if (!strcmp(arg, "-q") || !strcmp(arg, "--quiet")) {
+			quiet = 1;
+			continue;
+		}
+		if (!strcmp(arg, "-h") || !strcmp(arg, "--head")) {
+			show_head = 1;
+			continue;
+		}
+		if (!strcmp(arg, "-d") || !strcmp(arg, "--dereference")) {
+			deref_tags = 1;
+			continue;
+		}
+		if (!strcmp(arg, "-s") || !strcmp(arg, "--hash")) {
+			hash_only = 1;
+			continue;
+		}
+		if (!strcmp(arg, "--verify")) {
+			verify = 1;
+			continue;
+		}
+		if (!strcmp(arg, "--tags")) {
+			tags_only = 1;
+			continue;
+		}
+		if (!strcmp(arg, "--heads")) {
+			heads_only = 1;
+			continue;
+		}
+		usage(show_ref_usage);
+	}
+	if (show_head)
+		head_ref(show_ref, NULL);
+	for_each_ref(show_ref, NULL);
+	if (!found_match) {
+		if (verify && !quiet)
+			die("No match");
+		return 1;
+	}
+	return 0;
+}
diff --git a/builtin.h b/builtin.h
index fc704bae1..6bf0ace37 100644
--- a/builtin.h
+++ b/builtin.h
@@ -64,6 +64,7 @@ extern int cmd_version(int argc, const char **argv, const char *prefix);
 extern int cmd_whatchanged(int argc, const char **argv, const char *prefix);
 extern int cmd_write_tree(int argc, const char **argv, const char *prefix);
 extern int cmd_verify_pack(int argc, const char **argv, const char *prefix);
+extern int cmd_show_ref(int argc, const char **argv, const char *prefix);
 extern int cmd_pack_refs(int argc, const char **argv, const char *prefix);
 
 #endif
diff --git a/git-branch.sh b/git-branch.sh
index e0501ec23..2600e9c4a 100755
--- a/git-branch.sh
+++ b/git-branch.sh
@@ -21,7 +21,7 @@ delete_branch () {
 	,,)
 	    die "What branch are you on anyway?" ;;
 	esac
-	branch=$(cat "$GIT_DIR/refs/heads/$branch_name") &&
+	branch=$(git-show-ref --verify --hash -- "refs/heads/$branch_name") &&
 	    branch=$(git-rev-parse --verify "$branch^0") ||
 		die "Seriously, what branch are you talking about?"
 	case "$option" in
@@ -112,7 +112,7 @@ rev=$(git-rev-parse --verify "$head") || exit
 git-check-ref-format "heads/$branchname" ||
 	die "we do not like '$branchname' as a branch name."
 
-if [ -e "$GIT_DIR/refs/heads/$branchname" ]
+if git-show-ref --verify --quiet -- "refs/heads/$branchname"
 then
 	if test '' = "$force"
 	then
diff --git a/git-checkout.sh b/git-checkout.sh
index c60e029b6..f03620b05 100755
--- a/git-checkout.sh
+++ b/git-checkout.sh
@@ -22,7 +22,7 @@ while [ "$#" != "0" ]; do
 		shift
 		[ -z "$newbranch" ] &&
 			die "git checkout: -b needs a branch name"
-		git-rev-parse --symbolic "heads/$newbranch" >&/dev/null &&
+		git-show-ref --verify --quiet -- "refs/heads/$newbranch" &&
 			die "git checkout: branch $newbranch already exists"
 		git-check-ref-format "heads/$newbranch" ||
 			die "git checkout: we do not like '$newbranch' as a branch name."
@@ -51,7 +51,8 @@ while [ "$#" != "0" ]; do
 			fi
 			new="$rev"
 			new_name="$arg^0"
-			if git-rev-parse "heads/$arg^0" >&/dev/null; then
+			if git-show-ref --verify --quiet -- "refs/heads/$arg"
+			then
 				branch="$arg"
 			fi
 		elif rev=$(git-rev-parse --verify "$arg^{tree}" 2>/dev/null)
diff --git a/git.c b/git.c
index 561be303d..f7e784164 100644
--- a/git.c
+++ b/git.c
@@ -270,6 +270,7 @@ static void handle_internal_command(int argc, const char **argv, char **envp)
 		{ "whatchanged", cmd_whatchanged, RUN_SETUP | USE_PAGER },
 		{ "write-tree", cmd_write_tree, RUN_SETUP },
 		{ "verify-pack", cmd_verify_pack },
+		{ "show-ref", cmd_show_ref, RUN_SETUP },
 		{ "pack-refs", cmd_pack_refs, RUN_SETUP },
 	};
 	int i;