update-ref and tag: add --create-reflog arg

Allow the creation of a ref (e.g. stash) with a reflog already in
place. For most refs (e.g. those under refs/heads), this happens
automatically, but for others, we need this option.

Currently, git does this by pre-creating the reflog, but alternate ref
backends might store reflogs somewhere other than .git/logs.  Code
that now directly manipulates .git/logs should instead use git
plumbing commands.

I also added --create-reflog to git tag, just for completeness.

In a moment, we will use this argument to make git stash work with
alternate ref backends.

Signed-off-by: David Turner <dturner@twopensource.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-tag.txt

@@ -13,7 +13,7 @@ SYNOPSIS
 	<tagname> [<commit> | <object>]
 'git tag' -d <tagname>...
 'git tag' [-n[<num>]] -l [--contains <commit>] [--points-at <object>]
-	[--column[=<options>] | --no-column] [<pattern>...]
+	[--column[=<options>] | --no-column] [--create-reflog] [<pattern>...]
 	[<pattern>...]
 'git tag' -v <tagname>...
 
@@ -143,6 +143,9 @@ This option is only applicable when listing tags without annotation lines.
 	all, 'whitespace' removes just leading/trailing whitespace lines and
 	'strip' removes both whitespace and commentary.
 
+--create-reflog::
+	Create a reflog for the tag.
+
 <tagname>::
 	The name of the tag to create, delete, or describe.
 	The new tag name must pass all checks defined by

Documentation/git-update-ref.txt

@@ -8,7 +8,7 @@ git-update-ref - Update the object name stored in a ref safely
 SYNOPSIS
 --------
 [verse]
-'git update-ref' [-m <reason>] (-d <ref> [<oldvalue>] | [--no-deref] <ref> <newvalue> [<oldvalue>] | --stdin [-z])
+'git update-ref' [-m <reason>] (-d <ref> [<oldvalue>] | [--no-deref] [--create-reflog] <ref> <newvalue> [<oldvalue>] | --stdin [-z])
 
 DESCRIPTION
 -----------
@@ -67,6 +67,9 @@ performs all modifications together.  Specify commands of the form:
 	verify SP <ref> [SP <oldvalue>] LF
 	option SP <opt> LF
 
+With `--create-reflog`, update-ref will create a reflog for each ref
+even if one would not ordinarily be created.
+
 Quote fields containing whitespace as if they were strings in C source
 code; i.e., surrounded by double-quotes and with backslash escapes.
 Use 40 "0" characters or the empty string to specify a zero value.  To

builtin/tag.c

@@ -579,6 +579,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 	struct create_tag_options opt;
 	char *cleanup_arg = NULL;
 	int annotate = 0, force = 0, lines = -1;
+	int create_reflog = 0;
 	int cmdmode = 0;
 	const char *msgfile = NULL, *keyid = NULL;
 	struct msg_arg msg = { 0, STRBUF_INIT };
@@ -605,6 +606,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 		OPT_STRING('u', "local-user", &keyid, N_("key-id"),
 					N_("use another key to sign the tag")),
 		OPT__FORCE(&force, N_("replace the tag if exists")),
+		OPT_BOOL(0, "create-reflog", &create_reflog, N_("create_reflog")),
 
 		OPT_GROUP(N_("Tag listing options")),
 		OPT_COLUMN(0, "column", &colopts, N_("show tag list in columns")),
@@ -733,7 +735,8 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 	transaction = ref_transaction_begin(&err);
 	if (!transaction ||
 	    ref_transaction_update(transaction, ref.buf, object, prev,
-				   0, NULL, &err) ||
+				   create_reflog ? REF_FORCE_CREATE_REFLOG : 0,
+				   NULL, &err) ||
 	    ref_transaction_commit(transaction, &err))
 		die("%s", err.buf);
 	ref_transaction_free(transaction);

builtin/update-ref.c

@@ -14,6 +14,7 @@ static const char * const git_update_ref_usage[] = {
 
 static char line_termination = '\n';
 static int update_flags;
+static unsigned create_reflog_flag;
 static const char *msg;
 
 /*
@@ -200,7 +201,8 @@ static const char *parse_cmd_update(struct ref_transaction *transaction,
 
 	if (ref_transaction_update(transaction, refname,
 				   new_sha1, have_old ? old_sha1 : NULL,
-				   update_flags, msg, &err))
+				   update_flags | create_reflog_flag,
+				   msg, &err))
 		die("%s", err.buf);
 
 	update_flags = 0;
@@ -231,7 +233,8 @@ static const char *parse_cmd_create(struct ref_transaction *transaction,
 		die("create %s: extra input: %s", refname, next);
 
 	if (ref_transaction_create(transaction, refname, new_sha1,
-				   update_flags, msg, &err))
+				   update_flags | create_reflog_flag,
+				   msg, &err))
 		die("%s", err.buf);
 
 	update_flags = 0;
@@ -354,6 +357,7 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
 	unsigned char sha1[20], oldsha1[20];
 	int delete = 0, no_deref = 0, read_stdin = 0, end_null = 0;
 	unsigned int flags = 0;
+	int create_reflog = 0;
 	struct option options[] = {
 		OPT_STRING( 'm', NULL, &msg, N_("reason"), N_("reason of the update")),
 		OPT_BOOL('d', NULL, &delete, N_("delete the reference")),
@@ -361,6 +365,7 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
 					N_("update <refname> not the one it points to")),
 		OPT_BOOL('z', NULL, &end_null, N_("stdin has NUL-terminated arguments")),
 		OPT_BOOL( 0 , "stdin", &read_stdin, N_("read updates from stdin")),
+		OPT_BOOL( 0 , "create-reflog", &create_reflog, N_("create_reflog")),
 		OPT_END(),
 	};
 
@@ -370,6 +375,8 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
 	if (msg && !*msg)
 		die("Refusing to perform update with empty message.");
 
+	create_reflog_flag = create_reflog ? REF_FORCE_CREATE_REFLOG : 0;
+
 	if (read_stdin) {
 		struct strbuf err = STRBUF_INIT;
 		struct ref_transaction *transaction;
@@ -418,5 +425,6 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
 		return delete_ref(refname, oldval ? oldsha1 : NULL, flags);
 	else
 		return update_ref(msg, refname, sha1, oldval ? oldsha1 : NULL,
-				  flags, UPDATE_REFS_DIE_ON_ERR);
+				  flags | create_reflog_flag,
+				  UPDATE_REFS_DIE_ON_ERR);
 }

t/t1400-update-ref.sh

@@ -23,6 +23,7 @@ test_expect_success setup '
 m=refs/heads/master
 n_dir=refs/heads/gu
 n=$n_dir/fixes
+outside=foo
 
 test_expect_success \
 	"create $m" \
@@ -74,6 +75,24 @@ test_expect_success "delete $m (by HEAD)" '
 '
 rm -f .git/$m
 
+test_expect_success 'update-ref does not create reflogs by default' '
+	test_when_finished "git update-ref -d $outside" &&
+	git update-ref $outside $A &&
+	git rev-parse $A >expect &&
+	git rev-parse $outside >actual &&
+	test_cmp expect actual &&
+	test_must_fail git reflog exists $outside
+'
+
+test_expect_success 'update-ref creates reflogs with --create-reflog' '
+	test_when_finished "git update-ref -d $outside" &&
+	git update-ref --create-reflog $outside $A &&
+	git rev-parse $A >expect &&
+	git rev-parse $outside >actual &&
+	test_cmp expect actual &&
+	git reflog exists $outside
+'
+
 test_expect_success \
 	"create $m (by HEAD)" \
 	"git update-ref HEAD $A &&
@@ -472,6 +491,25 @@ test_expect_success 'stdin create ref works' '
 	test_cmp expect actual
 '
 
+test_expect_success 'stdin does not create reflogs by default' '
+	test_when_finished "git update-ref -d $outside" &&
+	echo "create $outside $m" >stdin &&
+	git update-ref --stdin <stdin &&
+	git rev-parse $m >expect &&
+	git rev-parse $outside >actual &&
+	test_cmp expect actual &&
+	test_must_fail git reflog exists $outside
+'
+
+test_expect_success 'stdin creates reflogs with --create-reflog' '
+	echo "create $outside $m" >stdin &&
+	git update-ref --create-reflog --stdin <stdin &&
+	git rev-parse $m >expect &&
+	git rev-parse $outside >actual &&
+	test_cmp expect actual &&
+	git reflog exists $outside
+'
+
 test_expect_success 'stdin succeeds with quoted argument' '
 	git update-ref -d $a &&
 	echo "create $a \"$m\"" >stdin &&

t/t7004-tag.sh

@@ -51,7 +51,19 @@ test_expect_success 'creating a tag using default HEAD should succeed' '
 	echo foo >foo &&
 	git add foo &&
 	git commit -m Foo &&
-	git tag mytag
+	git tag mytag &&
+	test_must_fail git reflog exists refs/tags/mytag
+'
+
+test_expect_success 'creating a tag with --create-reflog should create reflog' '
+	test_when_finished "git tag -d tag_with_reflog" &&
+	git tag --create-reflog tag_with_reflog &&
+	git reflog exists refs/tags/tag_with_reflog
+'
+
+test_expect_success '--create-reflog does not create reflog on failure' '
+	test_must_fail git tag --create-reflog mytag &&
+	test_must_fail git reflog exists refs/tags/mytag
 '
 
 test_expect_success 'listing all tags if one exists should succeed' '