Sync with 2.16.6

* maint-2.16: (31 commits)
  Git 2.16.6
  test-drop-caches: use `has_dos_drive_prefix()`
  Git 2.15.4
  Git 2.14.6
  mingw: handle `subst`-ed "DOS drives"
  mingw: refuse to access paths with trailing spaces or periods
  mingw: refuse to access paths with illegal characters
  unpack-trees: let merged_entry() pass through do_add_entry()'s errors
  quote-stress-test: offer to test quoting arguments for MSYS2 sh
  t6130/t9350: prepare for stringent Win32 path validation
  quote-stress-test: allow skipping some trials
  quote-stress-test: accept arguments to test via the command-line
  tests: add a helper to stress test argument quoting
  mingw: fix quoting of arguments
  Disallow dubiously-nested submodule git directories
  protect_ntfs: turn on NTFS protection by default
  path: also guard `.gitmodules` against NTFS Alternate Data Streams
  is_ntfs_dotgit(): speed it up
  mingw: disallow backslash characters in tree objects' file names
  path: safeguard `.git` against NTFS Alternate Streams Accesses
  ...

t/t7416-submodule-dash-url.sh

@@ -46,4 +46,18 @@ test_expect_success 'fsck rejects unprotected dash' '
 	grep gitmodulesUrl err
 '
 
+test_expect_success 'trailing backslash is handled correctly' '
+	git init testmodule &&
+	test_commit -C testmodule c &&
+	git submodule add ./testmodule &&
+	: ensure that the name ends in a double backslash &&
+	sed -e "s|\\(submodule \"testmodule\\)\"|\\1\\\\\\\\\"|" \
+		-e "s|url = .*|url = \" --should-not-be-an-option\"|" \
+		<.gitmodules >.new &&
+	mv .new .gitmodules &&
+	git commit -am "Add testmodule" &&
+	test_must_fail git clone --verbose --recurse-submodules . dolly 2>err &&
+	test_i18ngrep ! "unknown option" err
+'
+
 test_done