builtin/refs: add "delete" subcommand

Reference-related functionality in Git is currently spread across many
different commands: git-update-ref(1), git-for-each-ref(1),
git-show-ref(1), git-pack-refs(1) and git-symbolic-ref(1). This makes it
hard for users to discover what functionality we have available to work
with references.

We have thus started to consolidate this functionality into git-refs(1),
which is a toolbox of everything related to references. Until now, the
command doesn't handle functionality of git-update-ref(1).

Fix this gap by introducing a new "delete" subcommand, which is the
equivalent of `git update-ref -d`.

Note that we're intentionally not using a generic "write" subcommand
with a "-d" flag. This is rather harder to discover, and subcommands
that are implmented as flags tend to be hard to reason about in the code
as we'd have to handle mutually-exclusive flags that stem from the other
subcommand-like modes.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-refs.adoc

@@ -20,6 +20,7 @@ git refs list [--count=<count>] [--shell|--perl|--python|--tcl]
 		   [ --stdin | (<pattern>...)]
 git refs exists <ref>
 git refs optimize [--all] [--no-prune] [--auto] [--include <pattern>] [--exclude <pattern>]
+git refs delete [--message=<reason>] [--no-deref] <ref> [<old-value>]
 
 DESCRIPTION
 -----------
@@ -51,6 +52,12 @@ optimize::
 	usage. This subcommand is an alias for linkgit:git-pack-refs[1] and
 	offers identical functionality.
 
+delete::
+	Delete the given reference. This subcommand mirrors `git update-ref -d`
+	(see linkgit:git-update-ref[1]). When `<old-value>` is given, the
+	reference is only deleted after verifying that it currently contains
+	`<old-value>`.
+
 OPTIONS
 -------
 
@@ -90,6 +97,16 @@ The following options are specific to 'git refs optimize':
 
 include::pack-refs-options.adoc[]
 
+The following options are specific to commands which write references:
+
+`--message=<reason>`::
+	Use the given <reason> string for the reflog entry associated with the
+	update. An empty message is rejected.
+
+`--no-deref`::
+	Operate on <ref> itself rather than the reference it points to via a
+	symbolic ref.
+
 KNOWN LIMITATIONS
 -----------------
 

builtin/refs.c

@@ -21,6 +21,9 @@
 #define REFS_OPTIMIZE_USAGE \
 	N_("git refs optimize " PACK_REFS_OPTS)
 
+#define REFS_DELETE_USAGE \
+	N_("git refs delete [--message=<reason>] [--no-deref] <ref> [<old-value>]")
+
 static int cmd_refs_migrate(int argc, const char **argv, const char *prefix,
 			    struct repository *repo)
 {
@@ -175,6 +178,52 @@ static int cmd_refs_optimize(int argc, const char **argv, const char *prefix,
 	return pack_refs_core(argc, argv, prefix, repo, refs_optimize_usage);
 }
 
+static int cmd_refs_delete(int argc, const char **argv, const char *prefix,
+			   struct repository *repo)
+{
+	static char const * const refs_delete_usage[] = {
+		REFS_DELETE_USAGE,
+		NULL
+	};
+	const char *message = NULL;
+	unsigned flags = 0;
+	struct option opts[] = {
+		OPT_STRING(0, "message", &message, N_("reason"),
+			   N_("reason of the update")),
+		OPT_BIT(0 ,"no-deref", &flags,
+			N_("update <refname> not the one it points to"),
+			REF_NO_DEREF),
+		OPT_END(),
+	};
+	struct object_id oldoid;
+	const char *refname;
+	int ret;
+
+	argc = parse_options(argc, argv, prefix, opts, refs_delete_usage, 0);
+	if (argc < 1 || argc > 2)
+		usage(_("delete requires reference name and an optional old object ID"));
+
+	if (message && !*message)
+		die(_("refusing to perform update with empty message"));
+
+	repo_config(repo, git_default_config, NULL);
+
+	refname = argv[0];
+	if (argc == 2) {
+		if (repo_get_oid_with_flags(repo, argv[1], &oldoid, GET_OID_SKIP_AMBIGUITY_CHECK))
+			die(_("invalid old object ID: '%s'"), argv[1]);
+		if (is_null_oid(&oldoid))
+			die(_("cannot delete reference with null old object ID"));
+	}
+
+	ret = refs_delete_ref(get_main_ref_store(repo), message, refname,
+			      argc == 2 ? &oldoid : NULL, flags);
+
+	if (ret < 0)
+		ret = 1;
+	return ret;
+}
+
 int cmd_refs(int argc,
 	     const char **argv,
 	     const char *prefix,
@@ -186,6 +235,7 @@ int cmd_refs(int argc,
 		"git refs list " COMMON_USAGE_FOR_EACH_REF,
 		REFS_EXISTS_USAGE,
 		REFS_OPTIMIZE_USAGE,
+		REFS_DELETE_USAGE,
 		NULL,
 	};
 	parse_opt_subcommand_fn *fn = NULL;
@@ -195,6 +245,7 @@ int cmd_refs(int argc,
 		OPT_SUBCOMMAND("list", &fn, cmd_refs_list),
 		OPT_SUBCOMMAND("exists", &fn, cmd_refs_exists),
 		OPT_SUBCOMMAND("optimize", &fn, cmd_refs_optimize),
+		OPT_SUBCOMMAND("delete", &fn, cmd_refs_delete),
 		OPT_END(),
 	};
 

t/meson.build

@@ -223,6 +223,7 @@ integration_tests = [
   't1461-refs-list.sh',
   't1462-refs-exists.sh',
   't1463-refs-optimize.sh',
+  't1464-refs-delete.sh',
   't1500-rev-parse.sh',
   't1501-work-tree.sh',
   't1502-rev-parse-parseopt.sh',

t/t1464-refs-delete.sh

@@ -0,0 +1,130 @@
+#!/bin/sh
+
+test_description='git refs delete'
+
+. ./test-lib.sh
+
+setup_repo () {
+	git init "$1" &&
+	test_commit -C "$1" A &&
+	test_commit -C "$1" B
+}
+
+test_expect_success 'delete without oldvalue verification' '
+	test_when_finished "rm -rf repo" &&
+	setup_repo repo &&
+	A=$(git -C repo rev-parse A) &&
+	git -C repo update-ref refs/heads/foo $A &&
+	git -C repo refs delete refs/heads/foo &&
+	test_must_fail git -C repo show-ref --verify -q refs/heads/foo
+'
+
+test_expect_success 'delete with matching oldvalue' '
+	test_when_finished "rm -rf repo" &&
+	setup_repo repo &&
+	(
+		cd repo &&
+		A=$(git rev-parse A) &&
+		git update-ref refs/heads/foo $A &&
+		git refs delete refs/heads/foo $A &&
+		test_must_fail git refs exists refs/heads/foo
+	)
+'
+
+test_expect_success 'delete with stale oldvalue fails' '
+	test_when_finished "rm -rf repo" &&
+	setup_repo repo &&
+	(
+		cd repo &&
+		A=$(git rev-parse A) &&
+		B=$(git rev-parse B) &&
+		git update-ref refs/heads/foo $A &&
+		test_must_fail git refs delete refs/heads/foo $B 2>err &&
+		test_grep " but expected " err &&
+		git refs exists refs/heads/foo
+	)
+'
+
+test_expect_success 'delete with null oldvalue fails' '
+	test_when_finished "rm -rf repo" &&
+	setup_repo repo &&
+	(
+		cd repo &&
+		A=$(git rev-parse A) &&
+		git update-ref refs/heads/foo $A &&
+		test_must_fail git refs delete refs/heads/foo $ZERO_OID 2>err &&
+		test_grep "null old object ID" err &&
+		git refs exists refs/heads/foo
+	)
+'
+
+test_expect_success 'delete with invalid oldvalue fails' '
+	test_when_finished "rm -rf repo" &&
+	setup_repo repo &&
+	(
+		cd repo &&
+		A=$(git rev-parse A) &&
+		git update-ref refs/heads/foo $A &&
+		test_must_fail git refs delete refs/heads/foo invalid-oid 2>err &&
+		test_grep "invalid old object ID" err &&
+		git refs exists refs/heads/foo
+	)
+'
+
+test_expect_success 'delete symref with --no-deref leaves target intact' '
+	test_when_finished "rm -rf repo" &&
+	setup_repo repo &&
+	(
+		cd repo &&
+		A=$(git rev-parse A) &&
+		git update-ref refs/heads/foo $A &&
+		git symbolic-ref refs/heads/symref refs/heads/foo &&
+		git refs delete --no-deref refs/heads/symref &&
+		test_must_fail git refs exists refs/heads/symref &&
+		git refs exists refs/heads/foo
+	)
+'
+
+test_expect_success 'delete with message records reason in reflog' '
+	test_when_finished "rm -rf repo" &&
+	setup_repo repo &&
+	(
+		cd repo &&
+		A=$(git rev-parse A) &&
+		git update-ref refs/heads/foo $A &&
+		git symbolic-ref HEAD refs/heads/foo &&
+		git refs delete --message=delete-reason refs/heads/foo &&
+		test_must_fail git refs exists refs/heads/foo &&
+		test-tool ref-store main for-each-reflog-ent HEAD >actual &&
+		test_grep "delete-reason$" actual
+	)
+'
+
+test_expect_success 'delete with empty message fails' '
+	test_when_finished "rm -rf repo" &&
+	setup_repo repo &&
+	(
+		cd repo &&
+		A=$(git rev-parse A) &&
+		git update-ref refs/heads/foo $A &&
+		test_must_fail git refs delete --message= refs/heads/foo 2>err &&
+		test_grep "empty message" err &&
+		git refs exists refs/heads/foo
+	)
+'
+
+test_expect_success 'delete without arguments fails' '
+	test_when_finished "rm -rf repo" &&
+	setup_repo repo &&
+	test_must_fail git -C repo refs delete 2>err &&
+	test_grep "requires reference name" err
+'
+
+test_expect_success 'delete with too many arguments fails' '
+	test_when_finished "rm -rf repo" &&
+	setup_repo repo &&
+	test_must_fail git refs delete one two three 2>err &&
+	test_grep "requires reference name" err
+'
+
+test_done