Merge branch 'sb/checkout-recurse-submodules'

"git checkout" is taught the "--recurse-submodules" option.

* sb/checkout-recurse-submodules:
  builtin/read-tree: add --recurse-submodules switch
  builtin/checkout: add --recurse-submodules switch
  entry.c: create submodules when interesting
  unpack-trees: check if we can perform the operation for submodules
  unpack-trees: pass old oid to verify_clean_submodule
  update submodules: add submodule_move_head
  submodule.c: get_super_prefix_or_empty
  update submodules: move up prepare_submodule_repo_env
  submodules: introduce check to see whether to touch a submodule
  update submodules: add a config option to determine if submodules are updated
  update submodules: add submodule config parsing
  make is_submodule_populated gently
  lib-submodule-update.sh: define tests for recursing into submodules
  lib-submodule-update.sh: replace sha1 by hash
  lib-submodule-update: teach test_submodule_content the -C <dir> flag
  lib-submodule-update.sh: do not use ./. as submodule remote
  lib-submodule-update.sh: reorder create_lib_submodule_repo
  submodule--helper.c: remove duplicate code
  connect_work_tree_and_git_dir: safely create leading directories

3 files changed, 586 insertions, 24 deletions

diff --git a/t/lib-submodule-update.sh b/t/lib-submodule-update.sh
index 915eb4a7c..fb4f7b014 100755
--- a/t/lib-submodule-update.sh
+++ b/t/lib-submodule-update.sh
@@ -4,6 +4,7 @@
 # - 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 =>
@@ -15,23 +16,50 @@
 # - Tracked file replaced by submodule (replace_sub1_with_file =>
 #   replace_file_with_sub1)
 #
-#                   --O-----O
-#                  /  ^     replace_directory_with_sub1
-#                 /   replace_sub1_with_directory
-#                /----O
-#               /     ^
-#              /      modify_sub1
-#      O------O-------O
-#      ^      ^\      ^
-#      |      | \     remove_sub1
-#      |      |  -----O-----O
-#      |      |   \   ^     replace_file_with_sub1
-#      |      |    \  replace_sub1_with_file
-#      |   add_sub1 --O-----O
-# no_submodule        ^     valid_sub1
-#                     invalid_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 &&
@@ -44,15 +72,16 @@ create_lib_submodule_repo () {
 		git branch "no_submodule" &&
 
 		git checkout -b "add_sub1" &&
-		git submodule add ./. sub1 &&
+		git submodule add ../submodule_update_sub1 sub1 &&
 		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 &&
+
+		git checkout -b remove_sub1 add_sub1 &&
 		git revert HEAD &&
 
-		git checkout -b "modify_sub1" "add_sub1" &&
+		git checkout -b modify_sub1 add_sub1 &&
 		git submodule update &&
 		(
 			cd sub1 &&
@@ -67,7 +96,27 @@ create_lib_submodule_repo () {
 		git add sub1 &&
 		git commit -m "Modify sub1" &&
 
-		git checkout -b "replace_sub1_with_directory" "add_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 &&
@@ -75,22 +124,25 @@ create_lib_submodule_repo () {
 		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 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 checkout -b invalid_sub1 add_sub1 &&
 		git update-index --cacheinfo 160000 0123456789012345678901234567890123456789 sub1 &&
 		git commit -m "Invalid sub1 commit" &&
 		git checkout -b valid_sub1 &&
 		git revert HEAD &&
+
 		git checkout master
 	)
 }
@@ -130,6 +182,15 @@ test_git_directory_is_unchanged () {
 	)
 }
 
+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.
@@ -151,15 +212,36 @@ reset_work_tree_to () {
 		git checkout -f "$1" &&
 		git status -u -s >actual &&
 		test_must_be_empty actual &&
-		sha1=$(git rev-parse --revs-only HEAD:sub1) &&
-		if test -n "$sha1" &&
-		   test $(cd "sub1" && git rev-parse --verify "$sha1^{commit}")
+		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
+		GIT_WORK_TREE=. git -C submodule_update/.git/modules/sub1/modules/sub2 config --unset core.worktree
+	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).
@@ -173,6 +255,11 @@ test_superproject_content () {
 # 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"
@@ -675,3 +762,464 @@ test_submodule_forced_switch () {
 		)
 	'
 }
+
+# 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.
+
+test_submodule_switch_recursing () {
+	command="$1"
+	RESULTDS=success
+	if test "$KNOWN_FAILURE_DIRECTORY_SUBMODULE_CONFLICTS" = 1
+	then
+		RESULTDS=failure
+	fi
+	RESULTR=success
+	if test "$KNOWN_FAILURE_SUBMODULE_RECURSIVE_NESTED" = 1
+	then
+		RESULTR=failure
+	fi
+	RESULTOI=success
+	if test "$KNOWN_FAILURE_SUBMODULE_OVERWRITE_IGNORED_UNTRACKED" = 1
+	then
+		RESULTOI=failure
+	fi
+	######################### 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 &&
+			$command add_sub1 &&
+			test_superproject_content origin/add_sub1 &&
+			test_submodule_content sub1 origin/add_sub1
+		)
+	'
+	# ... unless there is an untracked file in its place.
+	test_expect_success "$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
+			$command add_sub1 &&
+			test_superproject_content origin/add_sub1 &&
+			test_submodule_content sub1 origin/add_sub1
+		)
+	'
+	# Replacing a tracked file with a submodule produces a checked out submodule
+	test_expect_success "$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 &&
+			$command remove_sub1 &&
+			test_superproject_content origin/remove_sub1 &&
+			! test -e sub1
+		)
+	'
+	# ... absorbing a .git directory along the way.
+	test_expect_success "$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 &&
+			$command remove_sub1 &&
+			test_superproject_content origin/remove_sub1 &&
+			! test -e sub1 &&
+			test_git_directory_exists sub1
+		)
+	'
+	# Replacing a submodule with files in a directory must succeeds
+	# when the submodule is clean
+	test_expect_$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 &&
+			$command replace_sub1_with_directory &&
+			test_superproject_content origin/replace_sub1_with_directory &&
+			test_git_directory_exists sub1
+		)
+	'
+
+	# Replacing it with a file ...
+	test_expect_success "$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 &&
+			$command replace_sub1_with_file &&
+			test_superproject_content origin/replace_sub1_with_file &&
+			test -f sub1
+		)
+	'
+
+	# ... must check its local work tree for untracked files
+	test_expect_$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 $command replace_sub1_with_file &&
+			test_superproject_content origin/add_sub1 &&
+			test_submodule_content sub1 origin/add_sub1
+		)
+	'
+
+	# ... and ignored files are ignored
+	test_expect_success "$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 &&
+			: >sub1/ignored &&
+			$command replace_sub1_with_file &&
+			test_superproject_content origin/replace_sub1_with_file &&
+			test -f sub1
+		)
+	'
+
+	########################## Modified submodule #########################
+	# Updating a submodule sha1 updates the submodule's work tree
+	test_expect_success "$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 $command invalid_sub1 &&
+			test_superproject_content origin/add_sub1 &&
+			test_submodule_content sub1 origin/add_sub1
+		)
+	'
+
+	# recursing deeper than one level doesn't work yet.
+	test_expect_$RESULTR "$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
+		)
+	'
+}
+
+# Test that submodule contents are updated when switching between commits
+# that change a submodule, but throwing away local changes in
+# the superproject as well as the submodule is allowed.
+test_submodule_forced_switch_recursing () {
+	command="$1"
+	RESULT=success
+	if test "$KNOWN_FAILURE_DIRECTORY_SUBMODULE_CONFLICTS" = 1
+	then
+		RESULT=failure
+	fi
+	######################### Appearing submodule #########################
+	# Switching to a commit letting a submodule appear creates empty dir ...
+	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 &&
+			$command add_sub1 &&
+			test_superproject_content origin/add_sub1 &&
+			test_submodule_content sub1 origin/add_sub1
+		)
+	'
+	# ... and doesn't care if it already exists ...
+	test_expect_success "$command: added submodule ignores empty directory" '
+		prolog &&
+		reset_work_tree_to_interested no_submodule &&
+		(
+			cd submodule_update &&
+			git branch -t add_sub1 origin/add_sub1 &&
+			mkdir sub1 &&
+			$command add_sub1 &&
+			test_superproject_content origin/add_sub1 &&
+			test_submodule_content sub1 origin/add_sub1
+		)
+	'
+	# ... not caring about an untracked file either
+	test_expect_success "$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 &&
+			$command add_sub1 &&
+			test_superproject_content origin/add_sub1 &&
+			test_submodule_content sub1 origin/add_sub1
+		)
+	'
+	# Replacing a tracked file with a submodule checks out the submodule
+	test_expect_success "$command: replace tracked file with submodule populates the 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 &&
+			$command replace_directory_with_sub1 &&
+			test_superproject_content origin/replace_directory_with_sub1 &&
+			test_submodule_content sub1 origin/replace_directory_with_sub1
+		)
+	'
+
+	######################## Disappearing submodule #######################
+	# Removing a submodule doesn't remove its work tree ...
+	test_expect_success "$command: removed submodule leaves submodule directory and its contents in place" '
+		prolog &&
+		reset_work_tree_to_interested add_sub1 &&
+		(
+			cd submodule_update &&
+			git branch -t remove_sub1 origin/remove_sub1 &&
+			$command remove_sub1 &&
+			test_superproject_content origin/remove_sub1 &&
+			! test -e sub1
+		)
+	'
+	# ... especially when it contains a .git directory.
+	test_expect_success "$command: removed submodule leaves submodule containing a .git directory alone" '
+		prolog &&
+		reset_work_tree_to_interested add_sub1 &&
+		(
+			cd submodule_update &&
+			git branch -t remove_sub1 origin/remove_sub1 &&
+			replace_gitfile_with_git_dir sub1 &&
+			rm -rf .git/modules/sub1 &&
+			$command remove_sub1 &&
+			test_superproject_content origin/remove_sub1 &&
+			test_git_directory_exists sub1 &&
+			! test -e sub1
+		)
+	'
+	# Replacing a submodule with files in a directory ...
+	test_expect_success "$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 &&
+			$command replace_sub1_with_directory &&
+			test_superproject_content origin/replace_sub1_with_directory &&
+			test_submodule_content sub1 origin/modify_sub1
+			test_git_directory_exists sub1
+		)
+	'
+	# Replacing it with a file
+	test_expect_success "$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 &&
+			$command replace_sub1_with_file &&
+			test_superproject_content origin/replace_sub1_with_file
+		)
+	'
+
+	# ... even if the submodule contains ignored files
+	test_expect_success "$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 &&
+			$command replace_sub1_with_file &&
+			test_superproject_content origin/replace_sub1_with_file
+		)
+	'
+
+	# ... but stops for untracked files that would be lost
+	test_expect_$RESULT "$command: replace submodule with a file stops for 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/untracked_file &&
+			test_must_fail $command replace_sub1_with_file &&
+			test_superproject_content origin/add_sub1 &&
+			test -f sub1/untracked_file
+		)
+	'
+
+	########################## Modified submodule #########################
+	# Updating a submodule sha1 updates the submodule's work tree
+	test_expect_success "$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 &&
+			$command modify_sub1 &&
+			test_superproject_content origin/modify_sub1 &&
+			test_submodule_content sub1 origin/modify_sub1
+		)
+	'
+	# Updating a submodule to an invalid sha1 doesn't update the
+	# submodule's work tree, subsequent update will fail
+	test_expect_success "$command: modified submodule does not update submodule work tree to invalid commit" '
+		prolog &&
+		reset_work_tree_to_interested add_sub1 &&
+		(
+			cd submodule_update &&
+			git branch -t invalid_sub1 origin/invalid_sub1 &&
+			test_must_fail $command invalid_sub1 &&
+			test_superproject_content origin/add_sub1 &&
+			test_submodule_content sub1 origin/add_sub1
+		)
+	'
+	# Updating a submodule from an invalid sha1 updates
+	test_expect_success "$command: modified submodule does not 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 &&
+			test_must_fail $command valid_sub1 &&
+			test_superproject_content origin/invalid_sub1
+		)
+	'
+}
diff --git a/t/t1013-read-tree-submodule.sh b/t/t1013-read-tree-submodule.sh
index 20526aed3..de1ba02dc 100755
--- a/t/t1013-read-tree-submodule.sh
+++ b/t/t1013-read-tree-submodule.sh
@@ -5,6 +5,14 @@ test_description='read-tree can handle submodules'
 . ./test-lib.sh
 . "$TEST_DIRECTORY"/lib-submodule-update.sh
 
+KNOWN_FAILURE_SUBMODULE_RECURSIVE_NESTED=1
+KNOWN_FAILURE_DIRECTORY_SUBMODULE_CONFLICTS=1
+KNOWN_FAILURE_SUBMODULE_OVERWRITE_IGNORED_UNTRACKED=1
+
+test_submodule_switch_recursing "git read-tree --recurse-submodules -u -m"
+
+test_submodule_forced_switch_recursing "git read-tree --recurse-submodules -u --reset"
+
 test_submodule_switch "git read-tree -u -m"
 
 test_submodule_forced_switch "git read-tree -u --reset"
diff --git a/t/t2013-checkout-submodule.sh b/t/t2013-checkout-submodule.sh
index 6847f7582..e8f70b806 100755
--- a/t/t2013-checkout-submodule.sh
+++ b/t/t2013-checkout-submodule.sh
@@ -63,6 +63,12 @@ test_expect_success '"checkout <submodule>" honors submodule.*.ignore from .git/
 	! test -s actual
 '
 
+KNOWN_FAILURE_DIRECTORY_SUBMODULE_CONFLICTS=1
+KNOWN_FAILURE_SUBMODULE_RECURSIVE_NESTED=1
+test_submodule_switch_recursing "git checkout --recurse-submodules"
+
+test_submodule_forced_switch_recursing "git checkout -f --recurse-submodules"
+
 test_submodule_switch "git checkout"
 
 test_submodule_forced_switch "git checkout -f"