fixup! WIP tests: accommodate for BusyBox-w32

Author: dscho

t/test-lib.sh

@@ -1762,6 +1762,15 @@ Darwin)
 	test_set_prereq GREP_STRIPS_CR
 	test_set_prereq WINDOWS
 	GIT_TEST_CMP="GIT_DIR=/dev/null git diff --no-index --ignore-cr-at-eol --"
+	case "$($SHELL --help 2>&1)" in
+	*BusyBox*)
+		# Unlike the MSYS2 Bash, BusyBox does not translate /dev/null
+		# to the Windows null device when spawning the native git.exe,
+		# and the minimal CI SDK provides no /dev/null for it to open;
+		# name nul directly so test_cmp (and --ignore-cr-at-eol) works.
+		GIT_TEST_CMP="GIT_DIR=nul git diff --no-index --ignore-cr-at-eol --"
+		;;
+	esac
 	if ! type iconv >/dev/null 2>&1
 	then
 		iconv () {