merge(third_party/git): Merge squashed git subtree at v2.23.0 r/373

Merge commit '1b593e1ea4d2af0f6444d9a7788d5d99abd6fde5' as 'third_party/git'

1 files changed, 1034 insertions, 0 deletions

diff --git a/third_party/git/t/lib-submodule-update.sh b/third_party/git/t/lib-submodule-update.sh
new file mode 100755
index 000000000000..1dd17fc03e12
--- /dev/null
+++ b/third_party/git/t/lib-submodule-update.sh
@@ -0,0 +1,1034 @@
+# Create a submodule layout used for all tests below.
+#
+# The following use cases are covered:
+# - New submodule (no_submodule => add_sub1)
+# - Removed submodule (add_sub1 => remove_sub1)
+# - Updated submodule (add_sub1 => modify_sub1)
+# - Updated submodule recursively (add_nested_sub => modify_sub1_recursively)
+# - Submodule updated to invalid commit (add_sub1 => invalid_sub1)
+# - Submodule updated from invalid commit (invalid_sub1 => valid_sub1)
+# - Submodule replaced by tracked files in directory (add_sub1 =>
+#   replace_sub1_with_directory)
+# - Directory containing tracked files replaced by submodule
+#   (replace_sub1_with_directory => replace_directory_with_sub1)
+# - Submodule replaced by tracked file with the same name (add_sub1 =>
+#   replace_sub1_with_file)
+# - Tracked file replaced by submodule (replace_sub1_with_file =>
+#   replace_file_with_sub1)
+#
+#                     ----O
+#                    /    ^
+#                   /     remove_sub1
+#                  /
+#       add_sub1  /-------O---------O--------O  modify_sub1_recursively
+#             |  /        ^         add_nested_sub
+#             | /         modify_sub1
+#             v/
+#      O------O-----------O---------O
+#      ^       \          ^         replace_directory_with_sub1
+#      |        \         replace_sub1_with_directory
+# no_submodule   \
+#                 --------O---------O
+#                  \      ^         replace_file_with_sub1
+#                   \     replace_sub1_with_file
+#                    \
+#                     ----O---------O
+#                         ^         valid_sub1
+#                         invalid_sub1
+#
+
+create_lib_submodule_repo () {
+	git init submodule_update_sub1 &&
+	(
+		cd submodule_update_sub1 &&
+		echo "expect" >>.gitignore &&
+		echo "actual" >>.gitignore &&
+		echo "x" >file1 &&
+		echo "y" >file2 &&
+		git add .gitignore file1 file2 &&
+		git commit -m "Base inside first submodule" &&
+		git branch "no_submodule"
+	) &&
+	git init submodule_update_sub2 &&
+	(
+		cd submodule_update_sub2
+		echo "expect" >>.gitignore &&
+		echo "actual" >>.gitignore &&
+		echo "x" >file1 &&
+		echo "y" >file2 &&
+		git add .gitignore file1 file2 &&
+		git commit -m "nested submodule base" &&
+		git branch "no_submodule"
+	) &&
+	git init submodule_update_repo &&
+	(
+		cd submodule_update_repo &&
+		echo "expect" >>.gitignore &&
+		echo "actual" >>.gitignore &&
+		echo "x" >file1 &&
+		echo "y" >file2 &&
+		git add .gitignore file1 file2 &&
+		git commit -m "Base" &&
+		git branch "no_submodule" &&
+
+		git checkout -b "add_sub1" &&
+		git submodule add ../submodule_update_sub1 sub1 &&
+		git submodule add ../submodule_update_sub1 uninitialized_sub &&
+		git config -f .gitmodules submodule.sub1.ignore all &&
+		git config submodule.sub1.ignore all &&
+		git add .gitmodules &&
+		git commit -m "Add sub1" &&
+
+		git checkout -b remove_sub1 add_sub1 &&
+		git revert HEAD &&
+
+		git checkout -b modify_sub1 add_sub1 &&
+		git submodule update &&
+		(
+			cd sub1 &&
+			git fetch &&
+			git checkout -b "modifications" &&
+			echo "z" >file2 &&
+			echo "x" >file3 &&
+			git add file2 file3 &&
+			git commit -m "modified file2 and added file3" &&
+			git push origin modifications
+		) &&
+		git add sub1 &&
+		git commit -m "Modify sub1" &&
+
+		git checkout -b add_nested_sub modify_sub1 &&
+		git -C sub1 checkout -b "add_nested_sub" &&
+		git -C sub1 submodule add --branch no_submodule ../submodule_update_sub2 sub2 &&
+		git -C sub1 commit -a -m "add a nested submodule" &&
+		git add sub1 &&
+		git commit -a -m "update submodule, that updates a nested submodule" &&
+		git checkout -b modify_sub1_recursively &&
+		git -C sub1 checkout -b modify_sub1_recursively &&
+		git -C sub1/sub2 checkout -b modify_sub1_recursively &&
+		echo change >sub1/sub2/file3 &&
+		git -C sub1/sub2 add file3 &&
+		git -C sub1/sub2 commit -m "make a change in nested sub" &&
+		git -C sub1 add sub2 &&
+		git -C sub1 commit -m "update nested sub" &&
+		git add sub1 &&
+		git commit -m "update sub1, that updates nested sub" &&
+		git -C sub1 push origin modify_sub1_recursively &&
+		git -C sub1/sub2 push origin modify_sub1_recursively &&
+		git -C sub1 submodule deinit -f --all &&
+
+		git checkout -b replace_sub1_with_directory add_sub1 &&
+		git submodule update &&
+		git -C sub1 checkout modifications &&
+		git rm --cached sub1 &&
+		rm sub1/.git* &&
+		git config -f .gitmodules --remove-section "submodule.sub1" &&
+		git add .gitmodules sub1/* &&
+		git commit -m "Replace sub1 with directory" &&
+
+		git checkout -b replace_directory_with_sub1 &&
+		git revert HEAD &&
+
+		git checkout -b replace_sub1_with_file add_sub1 &&
+		git rm sub1 &&
+		echo "content" >sub1 &&
+		git add sub1 &&
+		git commit -m "Replace sub1 with file" &&
+
+		git checkout -b replace_file_with_sub1 &&
+		git revert HEAD &&
+
+		git checkout -b invalid_sub1 add_sub1 &&
+		git update-index --cacheinfo 160000 $(test_oid numeric) sub1 &&
+		git commit -m "Invalid sub1 commit" &&
+		git checkout -b valid_sub1 &&
+		git revert HEAD &&
+
+		git checkout master
+	)
+}
+
+# Helper function to replace gitfile with .git directory
+replace_gitfile_with_git_dir () {
+	(
+		cd "$1" &&
+		git_dir="$(git rev-parse --git-dir)" &&
+		rm -f .git &&
+		cp -R "$git_dir" .git &&
+		GIT_WORK_TREE=. git config --unset core.worktree
+	)
+}
+
+# Test that the .git directory in the submodule is unchanged (except for the
+# core.worktree setting, which appears only in $GIT_DIR/modules/$1/config).
+# Call this function before test_submodule_content as the latter might
+# write the index file leading to false positive index differences.
+#
+# Note that this only supports submodules at the root level of the
+# superproject, with the default name, i.e. same as its path.
+test_git_directory_is_unchanged () {
+	(
+		cd ".git/modules/$1" &&
+		# does core.worktree point at the right place?
+		test "$(git config core.worktree)" = "../../../$1" &&
+		# remove it temporarily before comparing, as
+		# "$1/.git/config" lacks it...
+		git config --unset core.worktree
+	) &&
+	diff -r ".git/modules/$1" "$1/.git" &&
+	(
+		# ... and then restore.
+		cd ".git/modules/$1" &&
+		git config core.worktree "../../../$1"
+	)
+}
+
+test_git_directory_exists() {
+	test -e ".git/modules/$1" &&
+	if test -f sub1/.git
+	then
+		# does core.worktree point at the right place?
+		test "$(git -C .git/modules/$1 config core.worktree)" = "../../../$1"
+	fi
+}
+
+# Helper function to be executed at the start of every test below, it sets up
+# the submodule repo if it doesn't exist and configures the most problematic
+# settings for diff.ignoreSubmodules.
+prolog () {
+	test_oid_init &&
+	(test -d submodule_update_repo || create_lib_submodule_repo) &&
+	test_config_global diff.ignoreSubmodules all &&
+	test_config diff.ignoreSubmodules all
+}
+
+# Helper function to bring work tree back into the state given by the
+# commit. This includes trying to populate sub1 accordingly if it exists and
+# should be updated to an existing commit.
+reset_work_tree_to () {
+	rm -rf submodule_update &&
+	git clone submodule_update_repo submodule_update &&
+	(
+		cd submodule_update &&
+		rm -rf sub1 &&
+		git checkout -f "$1" &&
+		git status -u -s >actual &&
+		test_must_be_empty actual &&
+		hash=$(git rev-parse --revs-only HEAD:sub1) &&
+		if test -n "$hash" &&
+		   test $(cd "../submodule_update_sub1" && git rev-parse --verify "$hash^{commit}")
+		then
+			git submodule update --init --recursive "sub1"
+		fi
+	)
+}
+
+reset_work_tree_to_interested () {
+	reset_work_tree_to $1 &&
+	# make the submodule git dirs available
+	if ! test -d submodule_update/.git/modules/sub1
+	then
+		mkdir -p submodule_update/.git/modules &&
+		cp -r submodule_update_repo/.git/modules/sub1 submodule_update/.git/modules/sub1
+		GIT_WORK_TREE=. git -C submodule_update/.git/modules/sub1 config --unset core.worktree
+	fi &&
+	if ! test -d submodule_update/.git/modules/sub1/modules/sub2
+	then
+		mkdir -p submodule_update/.git/modules/sub1/modules &&
+		cp -r submodule_update_repo/.git/modules/sub1/modules/sub2 submodule_update/.git/modules/sub1/modules/sub2
+		# core.worktree is unset for sub2 as it is not checked out
+	fi &&
+	# indicate we are interested in the submodule:
+	git -C submodule_update config submodule.sub1.url "bogus" &&
+	# sub1 might not be checked out, so use the git dir
+	git -C submodule_update/.git/modules/sub1 config submodule.sub2.url "bogus"
+}
+
+# Test that the superproject contains the content according to commit "$1"
+# (the work tree must match the index for everything but submodules but the
+# index must exactly match the given commit including any submodule SHA-1s).
+test_superproject_content () {
+	git diff-index --cached "$1" >actual &&
+	test_must_be_empty actual &&
+	git diff-files --ignore-submodules >actual &&
+	test_must_be_empty actual
+}
+
+# Test that the given submodule at path "$1" contains the content according
+# to the submodule commit recorded in the superproject's commit "$2"
+test_submodule_content () {
+	if test x"$1" = "x-C"
+	then
+		cd "$2"
+		shift; shift;
+	fi
+	if test $# != 2
+	then
+		echo "test_submodule_content needs two arguments"
+		return 1
+	fi &&
+	submodule="$1" &&
+	commit="$2" &&
+	test -d "$submodule"/ &&
+	if ! test -f "$submodule"/.git && ! test -d "$submodule"/.git
+	then
+		echo "Submodule $submodule is not populated"
+		return 1
+	fi &&
+	sha1=$(git rev-parse --verify "$commit:$submodule") &&
+	if test -z "$sha1"
+	then
+		echo "Couldn't retrieve SHA-1 of $submodule for $commit"
+		return 1
+	fi &&
+	(
+		cd "$submodule" &&
+		git status -u -s >actual &&
+		test_must_be_empty actual &&
+		git diff "$sha1" >actual &&
+		test_must_be_empty actual
+	)
+}
+
+# Test that the following transitions are correctly handled:
+# - Updated submodule
+# - New submodule
+# - Removed submodule
+# - Directory containing tracked files replaced by submodule
+# - Submodule replaced by tracked files in directory
+# - Submodule replaced by tracked file with the same name
+# - tracked file replaced by submodule
+#
+# The default is that submodule contents aren't changed until "git submodule
+# update" is run. And even then that command doesn't delete the work tree of
+# a removed submodule.
+#
+# Removing a submodule containing a .git directory must fail even when forced
+# to protect the history!
+#
+
+# Internal function; use test_submodule_switch() or
+# test_submodule_forced_switch() instead.
+test_submodule_switch_common() {
+	command="$1"
+	######################### Appearing submodule #########################
+	# Switching to a commit letting a submodule appear creates empty dir ...
+	if test "$KNOWN_FAILURE_STASH_DOES_IGNORE_SUBMODULE_CHANGES" = 1
+	then
+		# Restoring stash fails to restore submodule index entry
+		RESULT="failure"
+	else
+		RESULT="success"
+	fi
+	test_expect_$RESULT "$command: added submodule creates empty directory" '
+		prolog &&
+		reset_work_tree_to no_submodule &&
+		(
+			cd submodule_update &&
+			git branch -t add_sub1 origin/add_sub1 &&
+			$command add_sub1 &&
+			test_superproject_content origin/add_sub1 &&
+			test_dir_is_empty sub1 &&
+			git submodule update --init --recursive &&
+			test_submodule_content sub1 origin/add_sub1
+		)
+	'
+	# ... and doesn't care if it already exists.
+	test_expect_$RESULT "$command: added submodule leaves existing empty directory alone" '
+		prolog &&
+		reset_work_tree_to no_submodule &&
+		(
+			cd submodule_update &&
+			mkdir sub1 &&
+			git branch -t add_sub1 origin/add_sub1 &&
+			$command add_sub1 &&
+			test_superproject_content origin/add_sub1 &&
+			test_dir_is_empty sub1 &&
+			git submodule update --init --recursive &&
+			test_submodule_content sub1 origin/add_sub1
+		)
+	'
+	# Replacing a tracked file with a submodule produces an empty
+	# directory ...
+	test_expect_$RESULT "$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 &&
+			$command replace_file_with_sub1 &&
+			test_superproject_content origin/replace_file_with_sub1 &&
+			test_dir_is_empty sub1 &&
+			git submodule update --init --recursive &&
+			test_submodule_content sub1 origin/replace_file_with_sub1
+		)
+	'
+	# ... as does removing a directory with tracked files with a
+	# submodule.
+	if test "$KNOWN_FAILURE_NOFF_MERGE_DOESNT_CREATE_EMPTY_SUBMODULE_DIR" = 1
+	then
+		# Non fast-forward merges fail with "Directory sub1 doesn't
+		# exist. sub1" because the empty submodule directory is not
+		# created
+		RESULT="failure"
+	else
+		RESULT="success"
+	fi
+	test_expect_$RESULT "$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 &&
+			$command replace_directory_with_sub1 &&
+			test_superproject_content origin/replace_directory_with_sub1 &&
+			test_dir_is_empty sub1 &&
+			git submodule update --init --recursive &&
+			test_submodule_content sub1 origin/replace_directory_with_sub1
+		)
+	'
+
+	######################## Disappearing submodule #######################
+	# Removing a submodule doesn't remove its work tree ...
+	if test "$KNOWN_FAILURE_STASH_DOES_IGNORE_SUBMODULE_CHANGES" = 1
+	then
+		RESULT="failure"
+	else
+		RESULT="success"
+	fi
+	test_expect_$RESULT "$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 &&
+			$command remove_sub1 &&
+			test_superproject_content origin/remove_sub1 &&
+			test_submodule_content sub1 origin/add_sub1
+		)
+	'
+	# ... especially when it contains a .git directory.
+	test_expect_$RESULT "$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 &&
+			$command remove_sub1 &&
+			test_superproject_content origin/remove_sub1 &&
+			test_git_directory_is_unchanged sub1 &&
+			test_submodule_content sub1 origin/add_sub1
+		)
+	'
+	# Replacing a submodule with files in a directory must fail as the
+	# submodule work tree isn't removed ...
+	if test "$KNOWN_FAILURE_NOFF_MERGE_ATTEMPTS_TO_MERGE_REMOVED_SUBMODULE_FILES" = 1
+	then
+		# Non fast-forward merges attempt to merge the former
+		# submodule files with the newly checked out ones in the
+		# directory of the same name while it shouldn't.
+		RESULT="failure"
+	elif test "$KNOWN_FAILURE_FORCED_SWITCH_TESTS" = 1
+	then
+		# All existing tests that use test_submodule_forced_switch()
+		# require this.
+		RESULT="failure"
+	else
+		RESULT="success"
+	fi
+	test_expect_$RESULT "$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 $command replace_sub1_with_directory &&
+			test_superproject_content origin/add_sub1 &&
+			test_submodule_content sub1 origin/add_sub1
+		)
+	'
+	# ... especially when it contains a .git directory.
+	test_expect_$RESULT "$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 $command replace_sub1_with_file &&
+			test_superproject_content origin/add_sub1 &&
+			test_git_directory_is_unchanged sub1 &&
+			test_submodule_content sub1 origin/add_sub1
+		)
+	'
+
+	########################## Modified submodule #########################
+	# Updating a submodule sha1 doesn't update the submodule's work tree
+	if test "$KNOWN_FAILURE_CHERRY_PICK_SEES_EMPTY_COMMIT" = 1
+	then
+		# When cherry picking a SHA-1 update for an ignored submodule
+		# the commit incorrectly fails with "The previous cherry-pick
+		# is now empty, possibly due to conflict resolution."
+		RESULT="failure"
+	else
+		RESULT="success"
+	fi
+	test_expect_$RESULT "$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 &&
+			$command modify_sub1 &&
+			test_superproject_content origin/modify_sub1 &&
+			test_submodule_content sub1 origin/add_sub1 &&
+			git submodule update &&
+			test_submodule_content sub1 origin/modify_sub1
+		)
+	'
+	# Updating a submodule to an invalid sha1 doesn't update the
+	# submodule's work tree, subsequent update will fail
+	test_expect_$RESULT "$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 &&
+			$command invalid_sub1 &&
+			test_superproject_content origin/invalid_sub1 &&
+			test_submodule_content sub1 origin/add_sub1 &&
+			test_must_fail git submodule update &&
+			test_submodule_content sub1 origin/add_sub1
+		)
+	'
+	# Updating a submodule from an invalid sha1 doesn't update the
+	# submodule's work tree, subsequent update will succeed
+	test_expect_$RESULT "$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
+		)
+	'
+}
+
+# Declares and invokes several tests that, in various situations, checks that
+# 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
+#
+# If the command under test is known to not work with submodules in certain
+# conditions, set the appropriate KNOWN_FAILURE_* variable used in the tests
+# below to 1.
+#
+# 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="$1"
+	KNOWN_FAILURE_FORCED_SWITCH_TESTS=1
+	test_submodule_switch_common "$command"
+
+	# When forced, a file in the superproject does not prevent creating a
+	# submodule of the same name.
+	test_expect_success "$command: added submodule does remove untracked unignored file with same name when forced" '
+		prolog &&
+		reset_work_tree_to no_submodule &&
+		(
+			cd submodule_update &&
+			git branch -t add_sub1 origin/add_sub1 &&
+			>sub1 &&
+			$command add_sub1 &&
+			test_superproject_content origin/add_sub1 &&
+			test_dir_is_empty sub1
+		)
+	'
+}
+
+# Test that submodule contents are correctly updated when switching
+# between commits that change a submodule.
+# Test that the following transitions are correctly handled:
+# (These tests are also above in the case where we expect no change
+#  in the submodule)
+# - Updated submodule
+# - New submodule
+# - Removed submodule
+# - Directory containing tracked files replaced by submodule
+# - Submodule replaced by tracked files in directory
+# - Submodule replaced by tracked file with the same name
+# - tracked file replaced by submodule
+#
+# New test cases
+# - Removing a submodule with a git directory absorbs the submodules
+#   git directory first into the superproject.
+
+# Internal function; use test_submodule_switch_recursing_with_args() or
+# test_submodule_forced_switch_recursing_with_args() instead.
+test_submodule_recursing_with_args_common() {
+	command="$1"
+
+	######################### Appearing submodule #########################
+	# Switching to a commit letting a submodule appear checks it out ...
+	test_expect_success "$command: added submodule is checked out" '
+		prolog &&
+		reset_work_tree_to_interested no_submodule &&
+		(
+			cd submodule_update &&
+			git branch -t add_sub1 origin/add_sub1 &&
+			$command add_sub1 &&
+			test_superproject_content origin/add_sub1 &&
+			test_submodule_content sub1 origin/add_sub1
+		)
+	'
+	# ... ignoring an empty existing directory.
+	test_expect_success "$command: added submodule is checked out in empty dir" '
+		prolog &&
+		reset_work_tree_to_interested no_submodule &&
+		(
+			cd submodule_update &&
+			mkdir sub1 &&
+			git branch -t add_sub1 origin/add_sub1 &&
+			$command add_sub1 &&
+			test_superproject_content origin/add_sub1 &&
+			test_submodule_content sub1 origin/add_sub1
+		)
+	'
+	test_expect_success "$command: submodule branch is not changed, detach HEAD instead" '
+		prolog &&
+		reset_work_tree_to_interested add_sub1 &&
+		(
+			cd submodule_update &&
+			git -C sub1 checkout -b keep_branch &&
+			git -C sub1 rev-parse HEAD >expect &&
+			git branch -t modify_sub1 origin/modify_sub1 &&
+			$command modify_sub1 &&
+			test_superproject_content origin/modify_sub1 &&
+			test_submodule_content sub1 origin/modify_sub1 &&
+			git -C sub1 rev-parse keep_branch >actual &&
+			test_cmp expect actual &&
+			test_must_fail git -C sub1 symbolic-ref HEAD
+		)
+	'
+
+	# Replacing a tracked file with a submodule produces a checked out submodule
+	test_expect_success "$command: replace tracked file with submodule checks out submodule" '
+		prolog &&
+		reset_work_tree_to_interested replace_sub1_with_file &&
+		(
+			cd submodule_update &&
+			git branch -t replace_file_with_sub1 origin/replace_file_with_sub1 &&
+			$command replace_file_with_sub1 &&
+			test_superproject_content origin/replace_file_with_sub1 &&
+			test_submodule_content sub1 origin/replace_file_with_sub1
+		)
+	'
+	# ... as does removing a directory with tracked files with a submodule.
+	test_expect_success "$command: replace directory with submodule" '
+		prolog &&
+		reset_work_tree_to_interested replace_sub1_with_directory &&
+		(
+			cd submodule_update &&
+			git branch -t replace_directory_with_sub1 origin/replace_directory_with_sub1 &&
+			$command replace_directory_with_sub1 &&
+			test_superproject_content origin/replace_directory_with_sub1 &&
+			test_submodule_content sub1 origin/replace_directory_with_sub1
+		)
+	'
+
+	######################## Disappearing submodule #######################
+	# Removing a submodule removes its work tree ...
+	test_expect_success "$command: removed submodule removes submodules working tree" '
+		prolog &&
+		reset_work_tree_to_interested add_sub1 &&
+		(
+			cd submodule_update &&
+			git branch -t remove_sub1 origin/remove_sub1 &&
+			$command remove_sub1 &&
+			test_superproject_content origin/remove_sub1 &&
+			! test -e sub1 &&
+			test_must_fail git config -f .git/modules/sub1/config core.worktree
+		)
+	'
+	# ... absorbing a .git directory along the way.
+	test_expect_success "$command: removed submodule absorbs submodules .git directory" '
+		prolog &&
+		reset_work_tree_to_interested add_sub1 &&
+		(
+			cd submodule_update &&
+			git branch -t remove_sub1 origin/remove_sub1 &&
+			replace_gitfile_with_git_dir sub1 &&
+			rm -rf .git/modules &&
+			$command remove_sub1 &&
+			test_superproject_content origin/remove_sub1 &&
+			! test -e sub1 &&
+			test_git_directory_exists sub1
+		)
+	'
+
+	# Replacing it with a file ...
+	test_expect_success "$command: replace submodule with a file" '
+		prolog &&
+		reset_work_tree_to_interested add_sub1 &&
+		(
+			cd submodule_update &&
+			git branch -t replace_sub1_with_file origin/replace_sub1_with_file &&
+			$command replace_sub1_with_file &&
+			test_superproject_content origin/replace_sub1_with_file &&
+			test -f sub1
+		)
+	'
+	RESULTDS=success
+	if test "$KNOWN_FAILURE_DIRECTORY_SUBMODULE_CONFLICTS" = 1
+	then
+		RESULTDS=failure
+	fi
+	# ... must check its local work tree for untracked files
+	test_expect_$RESULTDS "$command: replace submodule with a file must fail with untracked files" '
+		prolog &&
+		reset_work_tree_to_interested add_sub1 &&
+		(
+			cd submodule_update &&
+			git branch -t replace_sub1_with_file origin/replace_sub1_with_file &&
+			: >sub1/untrackedfile &&
+			test_must_fail $command replace_sub1_with_file &&
+			test_superproject_content origin/add_sub1 &&
+			test_submodule_content sub1 origin/add_sub1 &&
+			test -f sub1/untracked_file
+		)
+	'
+
+	########################## Modified submodule #########################
+	# Updating a submodule sha1 updates the submodule's work tree
+	test_expect_success "$command: modified submodule updates submodule work tree" '
+		prolog &&
+		reset_work_tree_to_interested add_sub1 &&
+		(
+			cd submodule_update &&
+			git branch -t modify_sub1 origin/modify_sub1 &&
+			$command modify_sub1 &&
+			test_superproject_content origin/modify_sub1 &&
+			test_submodule_content sub1 origin/modify_sub1
+		)
+	'
+	# Updating a submodule to an invalid sha1 doesn't update the
+	# superproject nor the submodule's work tree.
+	test_expect_success "$command: updating to a missing submodule commit fails" '
+		prolog &&
+		reset_work_tree_to_interested add_sub1 &&
+		(
+			cd submodule_update &&
+			git branch -t invalid_sub1 origin/invalid_sub1 &&
+			test_must_fail $command invalid_sub1 2>err &&
+			test_i18ngrep sub1 err &&
+			test_superproject_content origin/add_sub1 &&
+			test_submodule_content sub1 origin/add_sub1
+		)
+	'
+}
+
+# Declares and invokes several tests that, in various situations, checks that
+# the provided Git command, when invoked with --recurse-submodules:
+#  - 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 updated
+#
+# Specify the Git command so that "git $GIT_COMMAND --recurse-submodules"
+# works.
+#
+# If the command under test is known to not work with submodules in certain
+# conditions, set the appropriate KNOWN_FAILURE_* variable used in the tests
+# below to 1.
+#
+# Use as follows:
+#
+# test_submodule_switch_recursing_with_args "$GIT_COMMAND"
+test_submodule_switch_recursing_with_args () {
+	cmd_args="$1"
+	command="git $cmd_args --recurse-submodules"
+	test_submodule_recursing_with_args_common "$command"
+
+	RESULTDS=success
+	if test "$KNOWN_FAILURE_DIRECTORY_SUBMODULE_CONFLICTS" = 1
+	then
+		RESULTDS=failure
+	fi
+	RESULTOI=success
+	if test "$KNOWN_FAILURE_SUBMODULE_OVERWRITE_IGNORED_UNTRACKED" = 1
+	then
+		RESULTOI=failure
+	fi
+	# Switching to a commit letting a submodule appear cannot override an
+	# untracked file.
+	test_expect_success "$command: added submodule doesn't remove untracked file with same name" '
+		prolog &&
+		reset_work_tree_to_interested no_submodule &&
+		(
+			cd submodule_update &&
+			git branch -t add_sub1 origin/add_sub1 &&
+			: >sub1 &&
+			test_must_fail $command add_sub1 &&
+			test_superproject_content origin/no_submodule &&
+			test_must_be_empty sub1
+		)
+	'
+	# ... but an ignored file is fine.
+	test_expect_$RESULTOI "$command: added submodule removes an untracked ignored file" '
+		test_when_finished "rm submodule_update/.git/info/exclude" &&
+		prolog &&
+		reset_work_tree_to_interested no_submodule &&
+		(
+			cd submodule_update &&
+			git branch -t add_sub1 origin/add_sub1 &&
+			: >sub1 &&
+			echo sub1 >.git/info/exclude &&
+			$command add_sub1 &&
+			test_superproject_content origin/add_sub1 &&
+			test_submodule_content sub1 origin/add_sub1
+		)
+	'
+
+	# Replacing a submodule with files in a directory must succeeds
+	# when the submodule is clean
+	test_expect_$RESULTDS "$command: replace submodule with a directory" '
+		prolog &&
+		reset_work_tree_to_interested add_sub1 &&
+		(
+			cd submodule_update &&
+			git branch -t replace_sub1_with_directory origin/replace_sub1_with_directory &&
+			$command replace_sub1_with_directory &&
+			test_superproject_content origin/replace_sub1_with_directory &&
+			test_submodule_content sub1 origin/replace_sub1_with_directory
+		)
+	'
+	# ... absorbing a .git directory.
+	test_expect_$RESULTDS "$command: replace submodule containing a .git directory with a directory must absorb the git dir" '
+		prolog &&
+		reset_work_tree_to_interested add_sub1 &&
+		(
+			cd submodule_update &&
+			git branch -t replace_sub1_with_directory origin/replace_sub1_with_directory &&
+			replace_gitfile_with_git_dir sub1 &&
+			rm -rf .git/modules &&
+			$command replace_sub1_with_directory &&
+			test_superproject_content origin/replace_sub1_with_directory &&
+			test_git_directory_exists sub1
+		)
+	'
+
+	# ... and ignored files are ignored
+	test_expect_success "$command: replace submodule with a file works ignores ignored files in submodule" '
+		test_when_finished "rm submodule_update/.git/modules/sub1/info/exclude" &&
+		prolog &&
+		reset_work_tree_to_interested add_sub1 &&
+		(
+			cd submodule_update &&
+			git branch -t replace_sub1_with_file origin/replace_sub1_with_file &&
+			echo ignored >.git/modules/sub1/info/exclude &&
+			: >sub1/ignored &&
+			$command replace_sub1_with_file &&
+			test_superproject_content origin/replace_sub1_with_file &&
+			test -f sub1
+		)
+	'
+
+	test_expect_success "git -c submodule.recurse=true $cmd_args: modified submodule updates submodule work tree" '
+		prolog &&
+		reset_work_tree_to_interested add_sub1 &&
+		(
+			cd submodule_update &&
+			git branch -t modify_sub1 origin/modify_sub1 &&
+			git -c submodule.recurse=true $cmd_args modify_sub1 &&
+			test_superproject_content origin/modify_sub1 &&
+			test_submodule_content sub1 origin/modify_sub1
+		)
+	'
+
+	# recursing deeper than one level doesn't work yet.
+	test_expect_success "$command: modified submodule updates submodule recursively" '
+		prolog &&
+		reset_work_tree_to_interested add_nested_sub &&
+		(
+			cd submodule_update &&
+			git branch -t modify_sub1_recursively origin/modify_sub1_recursively &&
+			$command modify_sub1_recursively &&
+			test_superproject_content origin/modify_sub1_recursively &&
+			test_submodule_content sub1 origin/modify_sub1_recursively &&
+			test_submodule_content -C sub1 sub2 origin/modify_sub1_recursively
+		)
+	'
+}
+
+# Same as test_submodule_switch_recursing_with_args(), except that throwing
+# away local changes in the superproject is allowed.
+test_submodule_forced_switch_recursing_with_args () {
+	cmd_args="$1"
+	command="git $cmd_args --recurse-submodules"
+	test_submodule_recursing_with_args_common "$command"
+
+	RESULT=success
+	if test "$KNOWN_FAILURE_DIRECTORY_SUBMODULE_CONFLICTS" = 1
+	then
+		RESULT=failure
+	fi
+	# Switching to a commit letting a submodule appear does not care about
+	# an untracked file.
+	test_expect_success "$command: added submodule does remove untracked unignored file with same name when forced" '
+		prolog &&
+		reset_work_tree_to_interested no_submodule &&
+		(
+			cd submodule_update &&
+			git branch -t add_sub1 origin/add_sub1 &&
+			>sub1 &&
+			$command add_sub1 &&
+			test_superproject_content origin/add_sub1 &&
+			test_submodule_content sub1 origin/add_sub1
+		)
+	'
+
+	# Replacing a submodule with files in a directory ...
+	test_expect_success "$command: replace submodule with a directory" '
+		prolog &&
+		reset_work_tree_to_interested add_sub1 &&
+		(
+			cd submodule_update &&
+			git branch -t replace_sub1_with_directory origin/replace_sub1_with_directory &&
+			$command replace_sub1_with_directory &&
+			test_superproject_content origin/replace_sub1_with_directory
+		)
+	'
+	# ... absorbing a .git directory.
+	test_expect_success "$command: replace submodule containing a .git directory with a directory must fail" '
+		prolog &&
+		reset_work_tree_to_interested add_sub1 &&
+		(
+			cd submodule_update &&
+			git branch -t replace_sub1_with_directory origin/replace_sub1_with_directory &&
+			replace_gitfile_with_git_dir sub1 &&
+			rm -rf .git/modules/sub1 &&
+			$command replace_sub1_with_directory &&
+			test_superproject_content origin/replace_sub1_with_directory &&
+			test_git_directory_exists sub1
+		)
+	'
+
+	# ... even if the submodule contains ignored files
+	test_expect_success "$command: replace submodule with a file ignoring ignored files" '
+		prolog &&
+		reset_work_tree_to_interested add_sub1 &&
+		(
+			cd submodule_update &&
+			git branch -t replace_sub1_with_file origin/replace_sub1_with_file &&
+			: >sub1/expect &&
+			$command replace_sub1_with_file &&
+			test_superproject_content origin/replace_sub1_with_file
+		)
+	'
+
+	# Updating a submodule from an invalid sha1 updates
+	test_expect_success "$command: modified submodule does update submodule work tree from invalid commit" '
+		prolog &&
+		reset_work_tree_to_interested invalid_sub1 &&
+		(
+			cd submodule_update &&
+			git branch -t valid_sub1 origin/valid_sub1 &&
+			$command valid_sub1 &&
+			test_superproject_content origin/valid_sub1 &&
+			test_submodule_content sub1 origin/valid_sub1
+		)
+	'
+
+	# Old versions of Git were buggy writing the .git link file
+	# (e.g. before f8eaa0ba98b and then moving the superproject repo
+	# whose submodules contained absolute paths)
+	test_expect_success "$command: updating submodules fixes .git links" '
+		prolog &&
+		reset_work_tree_to_interested add_sub1 &&
+		(
+			cd submodule_update &&
+			git branch -t modify_sub1 origin/modify_sub1 &&
+			echo "gitdir: bogus/path" >sub1/.git &&
+			$command modify_sub1 &&
+			test_superproject_content origin/modify_sub1 &&
+			test_submodule_content sub1 origin/modify_sub1
+		)
+	'
+
+	test_expect_success "$command: changed submodule worktree is reset" '
+		prolog &&
+		reset_work_tree_to_interested add_sub1 &&
+		(
+			cd submodule_update &&
+			rm sub1/file1 &&
+			: >sub1/new_file &&
+			git -C sub1 add new_file &&
+			$command HEAD &&
+			test_path_is_file sub1/file1 &&
+			test_path_is_missing sub1/new_file
+		)
+	'
+}