Merge branch 'mh/update-ref-errors'

Error handling in the codepaths that updates refs has been
improved.

* mh/update-ref-errors:
  lock_ref_for_update(): avoid a symref resolution
  lock_ref_for_update(): make error handling more uniform
  t1404: add more tests of update-ref error handling
  t1404: document function test_update_rejected
  t1404: remove "prefix" argument to test_update_rejected
  t1404: rename file to t1404-update-ref-errors.sh

3 files changed, 449 insertions, 213 deletions

diff --git a/refs/files-backend.c b/refs/files-backend.c
index 4dd72b42c8..1bf643025c 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -3389,6 +3389,38 @@ static const char *original_update_refname(struct ref_update *update)
 }
 
 /*
+ * Check whether the REF_HAVE_OLD and old_oid values stored in update
+ * are consistent with oid, which is the reference's current value. If
+ * everything is OK, return 0; otherwise, write an error message to
+ * err and return -1.
+ */
+static int check_old_oid(struct ref_update *update, struct object_id *oid,
+			 struct strbuf *err)
+{
+	if (!(update->flags & REF_HAVE_OLD) ||
+		   !hashcmp(oid->hash, update->old_sha1))
+		return 0;
+
+	if (is_null_sha1(update->old_sha1))
+		strbuf_addf(err, "cannot lock ref '%s': "
+			    "reference already exists",
+			    original_update_refname(update));
+	else if (is_null_oid(oid))
+		strbuf_addf(err, "cannot lock ref '%s': "
+			    "reference is missing but expected %s",
+			    original_update_refname(update),
+			    sha1_to_hex(update->old_sha1));
+	else
+		strbuf_addf(err, "cannot lock ref '%s': "
+			    "is at %s but expected %s",
+			    original_update_refname(update),
+			    oid_to_hex(oid),
+			    sha1_to_hex(update->old_sha1));
+
+	return -1;
+}
+
+/*
  * Prepare for carrying out update:
  * - Lock the reference referred to by update.
  * - Read the reference under lock.
@@ -3433,7 +3465,7 @@ static int lock_ref_for_update(struct ref_update *update,
 
 		reason = strbuf_detach(err, NULL);
 		strbuf_addf(err, "cannot lock ref '%s': %s",
-			    update->refname, reason);
+			    original_update_refname(update), reason);
 		free(reason);
 		return ret;
 	}
@@ -3447,28 +3479,17 @@ static int lock_ref_for_update(struct ref_update *update,
 			 * the transaction, so we have to read it here
 			 * to record and possibly check old_sha1:
 			 */
-			if (read_ref_full(update->refname,
-					  mustexist ? RESOLVE_REF_READING : 0,
+			if (read_ref_full(referent.buf, 0,
 					  lock->old_oid.hash, NULL)) {
 				if (update->flags & REF_HAVE_OLD) {
 					strbuf_addf(err, "cannot lock ref '%s': "
-						    "can't resolve old value",
-						    update->refname);
-					return TRANSACTION_GENERIC_ERROR;
-				} else {
-					hashclr(lock->old_oid.hash);
+						    "error reading reference",
+						    original_update_refname(update));
+					return -1;
 				}
-			}
-			if ((update->flags & REF_HAVE_OLD) &&
-			    hashcmp(lock->old_oid.hash, update->old_sha1)) {
-				strbuf_addf(err, "cannot lock ref '%s': "
-					    "is at %s but expected %s",
-					    update->refname,
-					    sha1_to_hex(lock->old_oid.hash),
-					    sha1_to_hex(update->old_sha1));
+			} else if (check_old_oid(update, &lock->old_oid, err)) {
 				return TRANSACTION_GENERIC_ERROR;
 			}
-
 		} else {
 			/*
 			 * Create a new update for the reference this
@@ -3485,6 +3506,9 @@ static int lock_ref_for_update(struct ref_update *update,
 	} else {
 		struct ref_update *parent_update;
 
+		if (check_old_oid(update, &lock->old_oid, err))
+			return TRANSACTION_GENERIC_ERROR;
+
 		/*
 		 * If this update is happening indirectly because of a
 		 * symref update, record the old SHA-1 in the parent
@@ -3495,20 +3519,6 @@ static int lock_ref_for_update(struct ref_update *update,
 		     parent_update = parent_update->parent_update) {
 			oidcpy(&parent_update->lock->old_oid, &lock->old_oid);
 		}
-
-		if ((update->flags & REF_HAVE_OLD) &&
-		    hashcmp(lock->old_oid.hash, update->old_sha1)) {
-			if (is_null_sha1(update->old_sha1))
-				strbuf_addf(err, "cannot lock ref '%s': reference already exists",
-					    original_update_refname(update));
-			else
-				strbuf_addf(err, "cannot lock ref '%s': is at %s but expected %s",
-					    original_update_refname(update),
-					    sha1_to_hex(lock->old_oid.hash),
-					    sha1_to_hex(update->old_sha1));
-
-			return TRANSACTION_GENERIC_ERROR;
-		}
 	}
 
 	if ((update->flags & REF_HAVE_NEW) &&
@@ -3530,7 +3540,7 @@ static int lock_ref_for_update(struct ref_update *update,
 			 */
 			update->lock = NULL;
 			strbuf_addf(err,
-				    "cannot update the ref '%s': %s",
+				    "cannot update ref '%s': %s",
 				    update->refname, write_err);
 			free(write_err);
 			return TRANSACTION_GENERIC_ERROR;
diff --git a/t/t1404-update-ref-df-conflicts.sh b/t/t1404-update-ref-df-conflicts.sh
deleted file mode 100755
index 6d869d1285..0000000000
--- a/t/t1404-update-ref-df-conflicts.sh
+++ /dev/null
@@ -1,181 +0,0 @@
-#!/bin/sh
-
-test_description='Test git update-ref with D/F conflicts'
-. ./test-lib.sh
-
-test_update_rejected () {
-	prefix="$1" &&
-	before="$2" &&
-	pack="$3" &&
-	create="$4" &&
-	error="$5" &&
-	printf "create $prefix/%s $C\n" $before |
-	git update-ref --stdin &&
-	git for-each-ref $prefix >unchanged &&
-	if $pack
-	then
-		git pack-refs --all
-	fi &&
-	printf "create $prefix/%s $C\n" $create >input &&
-	test_must_fail git update-ref --stdin <input 2>output.err &&
-	grep -F "$error" output.err &&
-	git for-each-ref $prefix >actual &&
-	test_cmp unchanged actual
-}
-
-Q="'"
-
-test_expect_success 'setup' '
-
-	git commit --allow-empty -m Initial &&
-	C=$(git rev-parse HEAD) &&
-	git commit --allow-empty -m Second &&
-	D=$(git rev-parse HEAD)
-
-'
-
-test_expect_success 'existing loose ref is a simple prefix of new' '
-
-	prefix=refs/1l &&
-	test_update_rejected $prefix "a c e" false "b c/x d" \
-		"$Q$prefix/c$Q exists; cannot create $Q$prefix/c/x$Q"
-
-'
-
-test_expect_success 'existing packed ref is a simple prefix of new' '
-
-	prefix=refs/1p &&
-	test_update_rejected $prefix "a c e" true "b c/x d" \
-		"$Q$prefix/c$Q exists; cannot create $Q$prefix/c/x$Q"
-
-'
-
-test_expect_success 'existing loose ref is a deeper prefix of new' '
-
-	prefix=refs/2l &&
-	test_update_rejected $prefix "a c e" false "b c/x/y d" \
-		"$Q$prefix/c$Q exists; cannot create $Q$prefix/c/x/y$Q"
-
-'
-
-test_expect_success 'existing packed ref is a deeper prefix of new' '
-
-	prefix=refs/2p &&
-	test_update_rejected $prefix "a c e" true "b c/x/y d" \
-		"$Q$prefix/c$Q exists; cannot create $Q$prefix/c/x/y$Q"
-
-'
-
-test_expect_success 'new ref is a simple prefix of existing loose' '
-
-	prefix=refs/3l &&
-	test_update_rejected $prefix "a c/x e" false "b c d" \
-		"$Q$prefix/c/x$Q exists; cannot create $Q$prefix/c$Q"
-
-'
-
-test_expect_success 'new ref is a simple prefix of existing packed' '
-
-	prefix=refs/3p &&
-	test_update_rejected $prefix "a c/x e" true "b c d" \
-		"$Q$prefix/c/x$Q exists; cannot create $Q$prefix/c$Q"
-
-'
-
-test_expect_success 'new ref is a deeper prefix of existing loose' '
-
-	prefix=refs/4l &&
-	test_update_rejected $prefix "a c/x/y e" false "b c d" \
-		"$Q$prefix/c/x/y$Q exists; cannot create $Q$prefix/c$Q"
-
-'
-
-test_expect_success 'new ref is a deeper prefix of existing packed' '
-
-	prefix=refs/4p &&
-	test_update_rejected $prefix "a c/x/y e" true "b c d" \
-		"$Q$prefix/c/x/y$Q exists; cannot create $Q$prefix/c$Q"
-
-'
-
-test_expect_success 'one new ref is a simple prefix of another' '
-
-	prefix=refs/5 &&
-	test_update_rejected $prefix "a e" false "b c c/x d" \
-		"cannot process $Q$prefix/c$Q and $Q$prefix/c/x$Q at the same time"
-
-'
-
-test_expect_success 'empty directory should not fool rev-parse' '
-	prefix=refs/e-rev-parse &&
-	git update-ref $prefix/foo $C &&
-	git pack-refs --all &&
-	mkdir -p .git/$prefix/foo/bar/baz &&
-	echo "$C" >expected &&
-	git rev-parse $prefix/foo >actual &&
-	test_cmp expected actual
-'
-
-test_expect_success 'empty directory should not fool for-each-ref' '
-	prefix=refs/e-for-each-ref &&
-	git update-ref $prefix/foo $C &&
-	git for-each-ref $prefix >expected &&
-	git pack-refs --all &&
-	mkdir -p .git/$prefix/foo/bar/baz &&
-	git for-each-ref $prefix >actual &&
-	test_cmp expected actual
-'
-
-test_expect_success 'empty directory should not fool create' '
-	prefix=refs/e-create &&
-	mkdir -p .git/$prefix/foo/bar/baz &&
-	printf "create %s $C\n" $prefix/foo |
-	git update-ref --stdin
-'
-
-test_expect_success 'empty directory should not fool verify' '
-	prefix=refs/e-verify &&
-	git update-ref $prefix/foo $C &&
-	git pack-refs --all &&
-	mkdir -p .git/$prefix/foo/bar/baz &&
-	printf "verify %s $C\n" $prefix/foo |
-	git update-ref --stdin
-'
-
-test_expect_success 'empty directory should not fool 1-arg update' '
-	prefix=refs/e-update-1 &&
-	git update-ref $prefix/foo $C &&
-	git pack-refs --all &&
-	mkdir -p .git/$prefix/foo/bar/baz &&
-	printf "update %s $D\n" $prefix/foo |
-	git update-ref --stdin
-'
-
-test_expect_success 'empty directory should not fool 2-arg update' '
-	prefix=refs/e-update-2 &&
-	git update-ref $prefix/foo $C &&
-	git pack-refs --all &&
-	mkdir -p .git/$prefix/foo/bar/baz &&
-	printf "update %s $D $C\n" $prefix/foo |
-	git update-ref --stdin
-'
-
-test_expect_success 'empty directory should not fool 0-arg delete' '
-	prefix=refs/e-delete-0 &&
-	git update-ref $prefix/foo $C &&
-	git pack-refs --all &&
-	mkdir -p .git/$prefix/foo/bar/baz &&
-	printf "delete %s\n" $prefix/foo |
-	git update-ref --stdin
-'
-
-test_expect_success 'empty directory should not fool 1-arg delete' '
-	prefix=refs/e-delete-1 &&
-	git update-ref $prefix/foo $C &&
-	git pack-refs --all &&
-	mkdir -p .git/$prefix/foo/bar/baz &&
-	printf "delete %s $C\n" $prefix/foo |
-	git update-ref --stdin
-'
-
-test_done
diff --git a/t/t1404-update-ref-errors.sh b/t/t1404-update-ref-errors.sh
new file mode 100755
index 0000000000..c34ece48f5
--- /dev/null
+++ b/t/t1404-update-ref-errors.sh
@@ -0,0 +1,407 @@
+#!/bin/sh
+
+test_description='Test git update-ref error handling'
+. ./test-lib.sh
+
+# Create some references, perhaps run pack-refs --all, then try to
+# create some more references. Ensure that the second creation fails
+# with the correct error message.
+# Usage: test_update_rejected <before> <pack> <create> <error>
+#   <before> is a ws-separated list of refs to create before the test
+#   <pack> (true or false) tells whether to pack the refs before the test
+#   <create> is a list of variables to attempt creating
+#   <error> is a string to look for in the stderr of update-ref.
+# All references are created in the namespace specified by the current
+# value of $prefix.
+test_update_rejected () {
+	before="$1" &&
+	pack="$2" &&
+	create="$3" &&
+	error="$4" &&
+	printf "create $prefix/%s $C\n" $before |
+	git update-ref --stdin &&
+	git for-each-ref $prefix >unchanged &&
+	if $pack
+	then
+		git pack-refs --all
+	fi &&
+	printf "create $prefix/%s $C\n" $create >input &&
+	test_must_fail git update-ref --stdin <input 2>output.err &&
+	grep -F "$error" output.err &&
+	git for-each-ref $prefix >actual &&
+	test_cmp unchanged actual
+}
+
+Q="'"
+
+test_expect_success 'setup' '
+
+	git commit --allow-empty -m Initial &&
+	C=$(git rev-parse HEAD) &&
+	git commit --allow-empty -m Second &&
+	D=$(git rev-parse HEAD) &&
+	git commit --allow-empty -m Third &&
+	E=$(git rev-parse HEAD)
+'
+
+test_expect_success 'existing loose ref is a simple prefix of new' '
+
+	prefix=refs/1l &&
+	test_update_rejected "a c e" false "b c/x d" \
+		"$Q$prefix/c$Q exists; cannot create $Q$prefix/c/x$Q"
+
+'
+
+test_expect_success 'existing packed ref is a simple prefix of new' '
+
+	prefix=refs/1p &&
+	test_update_rejected "a c e" true "b c/x d" \
+		"$Q$prefix/c$Q exists; cannot create $Q$prefix/c/x$Q"
+
+'
+
+test_expect_success 'existing loose ref is a deeper prefix of new' '
+
+	prefix=refs/2l &&
+	test_update_rejected "a c e" false "b c/x/y d" \
+		"$Q$prefix/c$Q exists; cannot create $Q$prefix/c/x/y$Q"
+
+'
+
+test_expect_success 'existing packed ref is a deeper prefix of new' '
+
+	prefix=refs/2p &&
+	test_update_rejected "a c e" true "b c/x/y d" \
+		"$Q$prefix/c$Q exists; cannot create $Q$prefix/c/x/y$Q"
+
+'
+
+test_expect_success 'new ref is a simple prefix of existing loose' '
+
+	prefix=refs/3l &&
+	test_update_rejected "a c/x e" false "b c d" \
+		"$Q$prefix/c/x$Q exists; cannot create $Q$prefix/c$Q"
+
+'
+
+test_expect_success 'new ref is a simple prefix of existing packed' '
+
+	prefix=refs/3p &&
+	test_update_rejected "a c/x e" true "b c d" \
+		"$Q$prefix/c/x$Q exists; cannot create $Q$prefix/c$Q"
+
+'
+
+test_expect_success 'new ref is a deeper prefix of existing loose' '
+
+	prefix=refs/4l &&
+	test_update_rejected "a c/x/y e" false "b c d" \
+		"$Q$prefix/c/x/y$Q exists; cannot create $Q$prefix/c$Q"
+
+'
+
+test_expect_success 'new ref is a deeper prefix of existing packed' '
+
+	prefix=refs/4p &&
+	test_update_rejected "a c/x/y e" true "b c d" \
+		"$Q$prefix/c/x/y$Q exists; cannot create $Q$prefix/c$Q"
+
+'
+
+test_expect_success 'one new ref is a simple prefix of another' '
+
+	prefix=refs/5 &&
+	test_update_rejected "a e" false "b c c/x d" \
+		"cannot process $Q$prefix/c$Q and $Q$prefix/c/x$Q at the same time"
+
+'
+
+test_expect_success 'empty directory should not fool rev-parse' '
+	prefix=refs/e-rev-parse &&
+	git update-ref $prefix/foo $C &&
+	git pack-refs --all &&
+	mkdir -p .git/$prefix/foo/bar/baz &&
+	echo "$C" >expected &&
+	git rev-parse $prefix/foo >actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'empty directory should not fool for-each-ref' '
+	prefix=refs/e-for-each-ref &&
+	git update-ref $prefix/foo $C &&
+	git for-each-ref $prefix >expected &&
+	git pack-refs --all &&
+	mkdir -p .git/$prefix/foo/bar/baz &&
+	git for-each-ref $prefix >actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'empty directory should not fool create' '
+	prefix=refs/e-create &&
+	mkdir -p .git/$prefix/foo/bar/baz &&
+	printf "create %s $C\n" $prefix/foo |
+	git update-ref --stdin
+'
+
+test_expect_success 'empty directory should not fool verify' '
+	prefix=refs/e-verify &&
+	git update-ref $prefix/foo $C &&
+	git pack-refs --all &&
+	mkdir -p .git/$prefix/foo/bar/baz &&
+	printf "verify %s $C\n" $prefix/foo |
+	git update-ref --stdin
+'
+
+test_expect_success 'empty directory should not fool 1-arg update' '
+	prefix=refs/e-update-1 &&
+	git update-ref $prefix/foo $C &&
+	git pack-refs --all &&
+	mkdir -p .git/$prefix/foo/bar/baz &&
+	printf "update %s $D\n" $prefix/foo |
+	git update-ref --stdin
+'
+
+test_expect_success 'empty directory should not fool 2-arg update' '
+	prefix=refs/e-update-2 &&
+	git update-ref $prefix/foo $C &&
+	git pack-refs --all &&
+	mkdir -p .git/$prefix/foo/bar/baz &&
+	printf "update %s $D $C\n" $prefix/foo |
+	git update-ref --stdin
+'
+
+test_expect_success 'empty directory should not fool 0-arg delete' '
+	prefix=refs/e-delete-0 &&
+	git update-ref $prefix/foo $C &&
+	git pack-refs --all &&
+	mkdir -p .git/$prefix/foo/bar/baz &&
+	printf "delete %s\n" $prefix/foo |
+	git update-ref --stdin
+'
+
+test_expect_success 'empty directory should not fool 1-arg delete' '
+	prefix=refs/e-delete-1 &&
+	git update-ref $prefix/foo $C &&
+	git pack-refs --all &&
+	mkdir -p .git/$prefix/foo/bar/baz &&
+	printf "delete %s $C\n" $prefix/foo |
+	git update-ref --stdin
+'
+
+# Test various errors when reading the old values of references...
+
+test_expect_success 'missing old value blocks update' '
+	prefix=refs/missing-update &&
+	cat >expected <<-EOF &&
+	fatal: cannot lock ref $Q$prefix/foo$Q: unable to resolve reference $Q$prefix/foo$Q
+	EOF
+	printf "%s\n" "update $prefix/foo $E $D" |
+	test_must_fail git update-ref --stdin 2>output.err &&
+	test_cmp expected output.err
+'
+
+test_expect_success 'incorrect old value blocks update' '
+	prefix=refs/incorrect-update &&
+	git update-ref $prefix/foo $C &&
+	cat >expected <<-EOF &&
+	fatal: cannot lock ref $Q$prefix/foo$Q: is at $C but expected $D
+	EOF
+	printf "%s\n" "update $prefix/foo $E $D" |
+	test_must_fail git update-ref --stdin 2>output.err &&
+	test_cmp expected output.err
+'
+
+test_expect_success 'existing old value blocks create' '
+	prefix=refs/existing-create &&
+	git update-ref $prefix/foo $C &&
+	cat >expected <<-EOF &&
+	fatal: cannot lock ref $Q$prefix/foo$Q: reference already exists
+	EOF
+	printf "%s\n" "create $prefix/foo $E" |
+	test_must_fail git update-ref --stdin 2>output.err &&
+	test_cmp expected output.err
+'
+
+test_expect_success 'incorrect old value blocks delete' '
+	prefix=refs/incorrect-delete &&
+	git update-ref $prefix/foo $C &&
+	cat >expected <<-EOF &&
+	fatal: cannot lock ref $Q$prefix/foo$Q: is at $C but expected $D
+	EOF
+	printf "%s\n" "delete $prefix/foo $D" |
+	test_must_fail git update-ref --stdin 2>output.err &&
+	test_cmp expected output.err
+'
+
+test_expect_success 'missing old value blocks indirect update' '
+	prefix=refs/missing-indirect-update &&
+	git symbolic-ref $prefix/symref $prefix/foo &&
+	cat >expected <<-EOF &&
+	fatal: cannot lock ref $Q$prefix/symref$Q: unable to resolve reference $Q$prefix/foo$Q
+	EOF
+	printf "%s\n" "update $prefix/symref $E $D" |
+	test_must_fail git update-ref --stdin 2>output.err &&
+	test_cmp expected output.err
+'
+
+test_expect_success 'incorrect old value blocks indirect update' '
+	prefix=refs/incorrect-indirect-update &&
+	git symbolic-ref $prefix/symref $prefix/foo &&
+	git update-ref $prefix/foo $C &&
+	cat >expected <<-EOF &&
+	fatal: cannot lock ref $Q$prefix/symref$Q: is at $C but expected $D
+	EOF
+	printf "%s\n" "update $prefix/symref $E $D" |
+	test_must_fail git update-ref --stdin 2>output.err &&
+	test_cmp expected output.err
+'
+
+test_expect_success 'existing old value blocks indirect create' '
+	prefix=refs/existing-indirect-create &&
+	git symbolic-ref $prefix/symref $prefix/foo &&
+	git update-ref $prefix/foo $C &&
+	cat >expected <<-EOF &&
+	fatal: cannot lock ref $Q$prefix/symref$Q: reference already exists
+	EOF
+	printf "%s\n" "create $prefix/symref $E" |
+	test_must_fail git update-ref --stdin 2>output.err &&
+	test_cmp expected output.err
+'
+
+test_expect_success 'incorrect old value blocks indirect delete' '
+	prefix=refs/incorrect-indirect-delete &&
+	git symbolic-ref $prefix/symref $prefix/foo &&
+	git update-ref $prefix/foo $C &&
+	cat >expected <<-EOF &&
+	fatal: cannot lock ref $Q$prefix/symref$Q: is at $C but expected $D
+	EOF
+	printf "%s\n" "delete $prefix/symref $D" |
+	test_must_fail git update-ref --stdin 2>output.err &&
+	test_cmp expected output.err
+'
+
+test_expect_success 'missing old value blocks indirect no-deref update' '
+	prefix=refs/missing-noderef-update &&
+	git symbolic-ref $prefix/symref $prefix/foo &&
+	cat >expected <<-EOF &&
+	fatal: cannot lock ref $Q$prefix/symref$Q: reference is missing but expected $D
+	EOF
+	printf "%s\n" "option no-deref" "update $prefix/symref $E $D" |
+	test_must_fail git update-ref --stdin 2>output.err &&
+	test_cmp expected output.err
+'
+
+test_expect_success 'incorrect old value blocks indirect no-deref update' '
+	prefix=refs/incorrect-noderef-update &&
+	git symbolic-ref $prefix/symref $prefix/foo &&
+	git update-ref $prefix/foo $C &&
+	cat >expected <<-EOF &&
+	fatal: cannot lock ref $Q$prefix/symref$Q: is at $C but expected $D
+	EOF
+	printf "%s\n" "option no-deref" "update $prefix/symref $E $D" |
+	test_must_fail git update-ref --stdin 2>output.err &&
+	test_cmp expected output.err
+'
+
+test_expect_success 'existing old value blocks indirect no-deref create' '
+	prefix=refs/existing-noderef-create &&
+	git symbolic-ref $prefix/symref $prefix/foo &&
+	git update-ref $prefix/foo $C &&
+	cat >expected <<-EOF &&
+	fatal: cannot lock ref $Q$prefix/symref$Q: reference already exists
+	EOF
+	printf "%s\n" "option no-deref" "create $prefix/symref $E" |
+	test_must_fail git update-ref --stdin 2>output.err &&
+	test_cmp expected output.err
+'
+
+test_expect_success 'incorrect old value blocks indirect no-deref delete' '
+	prefix=refs/incorrect-noderef-delete &&
+	git symbolic-ref $prefix/symref $prefix/foo &&
+	git update-ref $prefix/foo $C &&
+	cat >expected <<-EOF &&
+	fatal: cannot lock ref $Q$prefix/symref$Q: is at $C but expected $D
+	EOF
+	printf "%s\n" "option no-deref" "delete $prefix/symref $D" |
+	test_must_fail git update-ref --stdin 2>output.err &&
+	test_cmp expected output.err
+'
+
+test_expect_success 'non-empty directory blocks create' '
+	prefix=refs/ne-create &&
+	mkdir -p .git/$prefix/foo/bar &&
+	: >.git/$prefix/foo/bar/baz.lock &&
+	test_when_finished "rm -f .git/$prefix/foo/bar/baz.lock" &&
+	cat >expected <<-EOF &&
+	fatal: cannot lock ref $Q$prefix/foo$Q: there is a non-empty directory $Q.git/$prefix/foo$Q blocking reference $Q$prefix/foo$Q
+	EOF
+	printf "%s\n" "update $prefix/foo $C" |
+	test_must_fail git update-ref --stdin 2>output.err &&
+	test_cmp expected output.err &&
+	cat >expected <<-EOF &&
+	fatal: cannot lock ref $Q$prefix/foo$Q: unable to resolve reference $Q$prefix/foo$Q
+	EOF
+	printf "%s\n" "update $prefix/foo $D $C" |
+	test_must_fail git update-ref --stdin 2>output.err &&
+	test_cmp expected output.err
+'
+
+test_expect_success 'broken reference blocks create' '
+	prefix=refs/broken-create &&
+	mkdir -p .git/$prefix &&
+	echo "gobbledigook" >.git/$prefix/foo &&
+	test_when_finished "rm -f .git/$prefix/foo" &&
+	cat >expected <<-EOF &&
+	fatal: cannot lock ref $Q$prefix/foo$Q: unable to resolve reference $Q$prefix/foo$Q: reference broken
+	EOF
+	printf "%s\n" "update $prefix/foo $C" |
+	test_must_fail git update-ref --stdin 2>output.err &&
+	test_cmp expected output.err &&
+	cat >expected <<-EOF &&
+	fatal: cannot lock ref $Q$prefix/foo$Q: unable to resolve reference $Q$prefix/foo$Q: reference broken
+	EOF
+	printf "%s\n" "update $prefix/foo $D $C" |
+	test_must_fail git update-ref --stdin 2>output.err &&
+	test_cmp expected output.err
+'
+
+test_expect_success 'non-empty directory blocks indirect create' '
+	prefix=refs/ne-indirect-create &&
+	git symbolic-ref $prefix/symref $prefix/foo &&
+	mkdir -p .git/$prefix/foo/bar &&
+	: >.git/$prefix/foo/bar/baz.lock &&
+	test_when_finished "rm -f .git/$prefix/foo/bar/baz.lock" &&
+	cat >expected <<-EOF &&
+	fatal: cannot lock ref $Q$prefix/symref$Q: there is a non-empty directory $Q.git/$prefix/foo$Q blocking reference $Q$prefix/foo$Q
+	EOF
+	printf "%s\n" "update $prefix/symref $C" |
+	test_must_fail git update-ref --stdin 2>output.err &&
+	test_cmp expected output.err &&
+	cat >expected <<-EOF &&
+	fatal: cannot lock ref $Q$prefix/symref$Q: unable to resolve reference $Q$prefix/foo$Q
+	EOF
+	printf "%s\n" "update $prefix/symref $D $C" |
+	test_must_fail git update-ref --stdin 2>output.err &&
+	test_cmp expected output.err
+'
+
+test_expect_success 'broken reference blocks indirect create' '
+	prefix=refs/broken-indirect-create &&
+	git symbolic-ref $prefix/symref $prefix/foo &&
+	echo "gobbledigook" >.git/$prefix/foo &&
+	test_when_finished "rm -f .git/$prefix/foo" &&
+	cat >expected <<-EOF &&
+	fatal: cannot lock ref $Q$prefix/symref$Q: unable to resolve reference $Q$prefix/foo$Q: reference broken
+	EOF
+	printf "%s\n" "update $prefix/symref $C" |
+	test_must_fail git update-ref --stdin 2>output.err &&
+	test_cmp expected output.err &&
+	cat >expected <<-EOF &&
+	fatal: cannot lock ref $Q$prefix/symref$Q: unable to resolve reference $Q$prefix/foo$Q: reference broken
+	EOF
+	printf "%s\n" "update $prefix/symref $D $C" |
+	test_must_fail git update-ref --stdin 2>output.err &&
+	test_cmp expected output.err
+'
+
+test_done