Tests: clean up and document submodule helpers

Factor out the commonalities from test_submodule_switch() and
test_submodule_forced_switch() in lib-submodule-update.sh, and document
their usage.

This also makes explicit (through the KNOWN_FAILURE_FORCED_SWITCH_TESTS
variable) the fact that, currently, all functionality tested using
test_submodule_forced_switch() do not correctly handle the situation in
which a submodule is replaced with an ordinary directory.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/lib-submodule-update.sh

@@ -306,9 +306,9 @@ test_submodule_content () {
 # to protect the history!
 #
 
-# Test that submodule contents are currently not updated when switching
+# Internal function; use test_submodule_switch() or
-# between commits that change a submodule.
+# test_submodule_forced_switch() instead.
-test_submodule_switch () {
+test_submodule_switch_common() {
 	command="$1"
 	######################### Appearing submodule #########################
 	# Switching to a commit letting a submodule appear creates empty dir ...
@@ -332,7 +332,7 @@ test_submodule_switch () {
 			test_submodule_content sub1 origin/add_sub1
 		)
 	'
-	# ... and doesn't care if it already exists ...
+	# ... and doesn't care if it already exists.
 	test_expect_$RESULT "$command: added submodule leaves existing empty directory alone" '
 		prolog &&
 		reset_work_tree_to no_submodule &&
@@ -347,19 +347,6 @@ test_submodule_switch () {
 			test_submodule_content sub1 origin/add_sub1
 		)
 	'
-	# ... unless there is an untracked file in its place.
-	test_expect_success "$command: added submodule doesn't remove untracked unignored file with same name" '
-		prolog &&
-		reset_work_tree_to no_submodule &&
-		(
-			cd submodule_update &&
-			git branch -t add_sub1 origin/add_sub1 &&
-			>sub1 &&
-			test_must_fail $command add_sub1 &&
-			test_superproject_content origin/no_submodule &&
-			test_must_be_empty sub1
-		)
-	'
 	# Replacing a tracked file with a submodule produces an empty
 	# directory ...
 	test_expect_$RESULT "$command: replace tracked file with submodule creates empty directory" '
@@ -441,6 +428,11 @@ test_submodule_switch () {
 		# submodule files with the newly checked out ones in the
 		# directory of the same name while it shouldn't.
 		RESULT="failure"
+	elif test "$KNOWN_FAILURE_FORCED_SWITCH_TESTS" = 1
+	then
+		# All existing tests that use test_submodule_forced_switch()
+		# require this.
+		RESULT="failure"
 	else
 		RESULT="success"
 	fi
@@ -522,7 +514,6 @@ test_submodule_switch () {
 			test_submodule_content sub1 origin/modify_sub1
 		)
 	'
-
 	# Updating a submodule to an invalid sha1 doesn't update the
 	# submodule's work tree, subsequent update will fail
 	test_expect_$RESULT "$command: modified submodule does not update submodule work tree to invalid commit" '
@@ -555,42 +546,51 @@ test_submodule_switch () {
 	'
 }
 
-# Test that submodule contents are currently not updated when switching
+# Declares and invokes several tests that, in various situations, checks that
-# between commits that change a submodule, but throwing away local changes in
+# the provided transition function:
+#  - succeeds in updating the worktree and index of a superproject to a target
+#    commit, or fails atomically (depending on the test situation)
+#  - if succeeds, the contents of submodule directories are unchanged
+#  - if succeeds, once "git submodule update" is invoked, the contents of
+#    submodule directories are updated
+#
+# Use as follows:
+#
+# my_func () {
+#   target=$1
+#   # Do something here that updates the worktree and index to match target,
+#   # but not any submodule directories.
+# }
+# test_submodule_switch "my_func"
+test_submodule_switch () {
+	command="$1"
+	test_submodule_switch_common "$command"
+
+	# An empty directory does not prevent the creation of a submodule of
+	# the same name, but a file does.
+	test_expect_success "$command: added submodule doesn't remove untracked unignored file with same name" '
+		prolog &&
+		reset_work_tree_to no_submodule &&
+		(
+			cd submodule_update &&
+			git branch -t add_sub1 origin/add_sub1 &&
+			>sub1 &&
+			test_must_fail $command add_sub1 &&
+			test_superproject_content origin/no_submodule &&
+			test_must_be_empty sub1
+		)
+	'
+}
+
+# Same as test_submodule_switch(), except that throwing away local changes in
 # the superproject is allowed.
 test_submodule_forced_switch () {
 	command="$1"
-	######################### Appearing submodule #########################
+	KNOWN_FAILURE_FORCED_SWITCH_TESTS=1
-	# Switching to a commit letting a submodule appear creates empty dir ...
+	test_submodule_switch_common "$command"
-	test_expect_success "$command: added submodule creates empty directory" '
+
-		prolog &&
+	# When forced, a file in the superproject does not prevent creating a
-		reset_work_tree_to no_submodule &&
+	# submodule of the same name.
-		(
-			cd submodule_update &&
-			git branch -t add_sub1 origin/add_sub1 &&
-			$command add_sub1 &&
-			test_superproject_content origin/add_sub1 &&
-			test_dir_is_empty sub1 &&
-			git submodule update --init --recursive &&
-			test_submodule_content sub1 origin/add_sub1
-		)
-	'
-	# ... and doesn't care if it already exists ...
-	test_expect_success "$command: added submodule leaves existing empty directory alone" '
-		prolog &&
-		reset_work_tree_to no_submodule &&
-		(
-			cd submodule_update &&
-			git branch -t add_sub1 origin/add_sub1 &&
-			mkdir sub1 &&
-			$command add_sub1 &&
-			test_superproject_content origin/add_sub1 &&
-			test_dir_is_empty sub1 &&
-			git submodule update --init --recursive &&
-			test_submodule_content sub1 origin/add_sub1
-		)
-	'
-	# ... unless there is an untracked file in its place.
 	test_expect_success "$command: added submodule does remove untracked unignored file with same name when forced" '
 		prolog &&
 		reset_work_tree_to no_submodule &&
@@ -603,165 +603,6 @@ test_submodule_forced_switch () {
 			test_dir_is_empty sub1
 		)
 	'
-	# Replacing a tracked file with a submodule produces an empty
-	# directory ...
-	test_expect_success "$command: replace tracked file with submodule creates empty directory" '
-		prolog &&
-		reset_work_tree_to replace_sub1_with_file &&
-		(
-			cd submodule_update &&
-			git branch -t replace_file_with_sub1 origin/replace_file_with_sub1 &&
-			$command replace_file_with_sub1 &&
-			test_superproject_content origin/replace_file_with_sub1 &&
-			test_dir_is_empty sub1 &&
-			git submodule update --init --recursive &&
-			test_submodule_content sub1 origin/replace_file_with_sub1
-		)
-	'
-	# ... as does removing a directory with tracked files with a
-	# submodule.
-	test_expect_success "$command: replace directory with submodule" '
-		prolog &&
-		reset_work_tree_to replace_sub1_with_directory &&
-		(
-			cd submodule_update &&
-			git branch -t replace_directory_with_sub1 origin/replace_directory_with_sub1 &&
-			$command replace_directory_with_sub1 &&
-			test_superproject_content origin/replace_directory_with_sub1 &&
-			test_dir_is_empty sub1 &&
-			git submodule update --init --recursive &&
-			test_submodule_content sub1 origin/replace_directory_with_sub1
-		)
-	'
-
-	######################## Disappearing submodule #######################
-	# Removing a submodule doesn't remove its work tree ...
-	test_expect_success "$command: removed submodule leaves submodule directory and its contents in place" '
-		prolog &&
-		reset_work_tree_to add_sub1 &&
-		(
-			cd submodule_update &&
-			git branch -t remove_sub1 origin/remove_sub1 &&
-			$command remove_sub1 &&
-			test_superproject_content origin/remove_sub1 &&
-			test_submodule_content sub1 origin/add_sub1
-		)
-	'
-	# ... especially when it contains a .git directory.
-	test_expect_success "$command: removed submodule leaves submodule containing a .git directory alone" '
-		prolog &&
-		reset_work_tree_to add_sub1 &&
-		(
-			cd submodule_update &&
-			git branch -t remove_sub1 origin/remove_sub1 &&
-			replace_gitfile_with_git_dir sub1 &&
-			$command remove_sub1 &&
-			test_superproject_content origin/remove_sub1 &&
-			test_git_directory_is_unchanged sub1 &&
-			test_submodule_content sub1 origin/add_sub1
-		)
-	'
-	# Replacing a submodule with files in a directory must fail as the
-	# submodule work tree isn't removed ...
-	test_expect_failure "$command: replace submodule with a directory must fail" '
-		prolog &&
-		reset_work_tree_to add_sub1 &&
-		(
-			cd submodule_update &&
-			git branch -t replace_sub1_with_directory origin/replace_sub1_with_directory &&
-			test_must_fail $command replace_sub1_with_directory &&
-			test_superproject_content origin/add_sub1 &&
-			test_submodule_content sub1 origin/add_sub1
-		)
-	'
-	# ... especially when it contains a .git directory.
-	test_expect_failure "$command: replace submodule containing a .git directory with a directory must fail" '
-		prolog &&
-		reset_work_tree_to add_sub1 &&
-		(
-			cd submodule_update &&
-			git branch -t replace_sub1_with_directory origin/replace_sub1_with_directory &&
-			replace_gitfile_with_git_dir sub1 &&
-			test_must_fail $command replace_sub1_with_directory &&
-			test_superproject_content origin/add_sub1 &&
-			test_git_directory_is_unchanged sub1 &&
-			test_submodule_content sub1 origin/add_sub1
-		)
-	'
-	# Replacing it with a file must fail as it could throw away any local
-	# work tree changes ...
-	test_expect_failure "$command: replace submodule with a file must fail" '
-		prolog &&
-		reset_work_tree_to add_sub1 &&
-		(
-			cd submodule_update &&
-			git branch -t replace_sub1_with_file origin/replace_sub1_with_file &&
-			test_must_fail $command replace_sub1_with_file &&
-			test_superproject_content origin/add_sub1 &&
-			test_submodule_content sub1 origin/add_sub1
-		)
-	'
-	# ... or even destroy unpushed parts of submodule history if that
-	# still uses a .git directory.
-	test_expect_failure "$command: replace submodule containing a .git directory with a file must fail" '
-		prolog &&
-		reset_work_tree_to add_sub1 &&
-		(
-			cd submodule_update &&
-			git branch -t replace_sub1_with_file origin/replace_sub1_with_file &&
-			replace_gitfile_with_git_dir sub1 &&
-			test_must_fail $command replace_sub1_with_file &&
-			test_superproject_content origin/add_sub1 &&
-			test_git_directory_is_unchanged sub1 &&
-			test_submodule_content sub1 origin/add_sub1
-		)
-	'
-
-	########################## Modified submodule #########################
-	# Updating a submodule sha1 doesn't update the submodule's work tree
-	test_expect_success "$command: modified submodule does not update submodule work tree" '
-		prolog &&
-		reset_work_tree_to add_sub1 &&
-		(
-			cd submodule_update &&
-			git branch -t modify_sub1 origin/modify_sub1 &&
-			$command modify_sub1 &&
-			test_superproject_content origin/modify_sub1 &&
-			test_submodule_content sub1 origin/add_sub1 &&
-			git submodule update &&
-			test_submodule_content sub1 origin/modify_sub1
-		)
-	'
-	# Updating a submodule to an invalid sha1 doesn't update the
-	# submodule's work tree, subsequent update will fail
-	test_expect_success "$command: modified submodule does not update submodule work tree to invalid commit" '
-		prolog &&
-		reset_work_tree_to add_sub1 &&
-		(
-			cd submodule_update &&
-			git branch -t invalid_sub1 origin/invalid_sub1 &&
-			$command invalid_sub1 &&
-			test_superproject_content origin/invalid_sub1 &&
-			test_submodule_content sub1 origin/add_sub1 &&
-			test_must_fail git submodule update &&
-			test_submodule_content sub1 origin/add_sub1
-		)
-	'
-	# Updating a submodule from an invalid sha1 doesn't update the
-	# submodule's work tree, subsequent update will succeed
-	test_expect_success "$command: modified submodule does not update submodule work tree from invalid commit" '
-		prolog &&
-		reset_work_tree_to invalid_sub1 &&
-		(
-			cd submodule_update &&
-			git branch -t valid_sub1 origin/valid_sub1 &&
-			$command valid_sub1 &&
-			test_superproject_content origin/valid_sub1 &&
-			test_dir_is_empty sub1 &&
-			git submodule update --init --recursive &&
-			test_submodule_content sub1 origin/valid_sub1
-		)
-	'
 }
 
 # Test that submodule contents are correctly updated when switching