Merge branch 'sg/tests-prereq'

A lazily defined test prerequisite can now be defined in terms of
another lazily defined test prerequisite.

* sg/tests-prereq:
  tests: fix description of 'test_set_prereq'
  tests: make sure nested lazy prereqs work reliably

t/t0000-basic.sh

@@ -840,6 +840,27 @@ then
 	exit 1
 fi
 
+test_lazy_prereq NESTED_INNER '
+	>inner &&
+	rm -f outer
+'
+test_lazy_prereq NESTED_PREREQ '
+	>outer &&
+	test_have_prereq NESTED_INNER &&
+	echo "can create new file in cwd" >file &&
+	test -f outer &&
+	test ! -f inner
+'
+test_expect_success NESTED_PREREQ 'evaluating nested lazy prereqs dont interfere with each other' '
+	nestedworks=yes
+'
+
+if test -z "$GIT_TEST_FAIL_PREREQS_INTERNAL" && test "$nestedworks" != yes
+then
+	say 'bug in test framework: nested lazy prerequisites do not work'
+	exit 1
+fi
+
 test_expect_success 'lazy prereqs do not turn off tracing' "
 	run_sub_test_lib_test lazy-prereq-and-tracing \
 		'lazy prereqs and -x' -v -x <<-\\EOF &&

t/test-lib-functions.sh

@@ -423,7 +423,7 @@ write_script () {
 # - Explicitly using test_have_prereq.
 #
 # - Implicitly by specifying the prerequisite tag in the calls to
-#   test_expect_{success,failure,code}.
+#   test_expect_{success,failure} and test_external{,_without_stderr}.
 #
 # The single parameter is the prerequisite tag (a simple word, in all
 # capital letters by convention).
@@ -474,15 +474,15 @@ test_lazy_prereq () {
 
 test_run_lazy_prereq_ () {
 	script='
-mkdir -p "$TRASH_DIRECTORY/prereq-test-dir" &&
+mkdir -p "$TRASH_DIRECTORY/prereq-test-dir-'"$1"'" &&
 (
-	cd "$TRASH_DIRECTORY/prereq-test-dir" &&'"$2"'
+	cd "$TRASH_DIRECTORY/prereq-test-dir-'"$1"'" &&'"$2"'
 )'
 	say >&3 "checking prerequisite: $1"
 	say >&3 "$script"
 	test_eval_ "$script"
 	eval_ret=$?
-	rm -rf "$TRASH_DIRECTORY/prereq-test-dir"
+	rm -rf "$TRASH_DIRECTORY/prereq-test-dir-$1"
 	if test "$eval_ret" = 0; then
 		say >&3 "prerequisite $1 ok"
 	else