Merge branch 'jc/test-prereq' into maint

* jc/test-prereq:
  t3910: use the UTF8_NFD_TO_NFC test prereq
  test-lib: provide UTF8 behaviour as a prerequisite
  t0050: use the SYMLINKS test prereq
  t0050: use the CASE_INSENSITIVE_FS test prereq
  test-lib: provide case insensitivity as a prerequisite
  test: allow prerequisite to be evaluated lazily
  test: rename $satisfied to $satisfied_prereq

t/README

@@ -625,6 +625,15 @@ use these, and "test_set_prereq" for how to define your own.
    Git was compiled with USE_LIBPCRE=YesPlease. Wrap any tests
    that use git-grep --perl-regexp or git-grep -P in these.
 
+ - CASE_INSENSITIVE_FS
+
+   Test is run on a case insensitive file system.
+
+ - UTF8_NFD_TO_NFC
+
+   Test is run on a filesystem which converts decomposed utf-8 (nfd)
+   to precomposed utf-8 (nfc).
+
 Tips for Writing Tests
 ----------------------
 

t/t0003-attributes.sh

@@ -123,16 +123,6 @@ test_expect_success 'attribute matching is case insensitive when core.ignorecase
 
 '
 
-test_expect_success 'check whether FS is case-insensitive' '
-	mkdir junk &&
-	echo good >junk/CamelCase &&
-	echo bad >junk/camelcase &&
-	if test "$(cat junk/CamelCase)" != good
-	then
-		test_set_prereq CASE_INSENSITIVE_FS
-	fi
-'
-
 test_expect_success CASE_INSENSITIVE_FS 'additional case insensitivity tests' '
 	test_must_fail attr_check a/B/D/g "a/b/d/*" "-c core.ignorecase=0" &&
 	test_must_fail attr_check A/B/D/NO "a/b/d/*" "-c core.ignorecase=0" &&

t/t0050-filesystem.sh

@@ -7,48 +7,26 @@ test_description='Various filesystem issues'
 auml=$(printf '\303\244')
 aumlcdiar=$(printf '\141\314\210')
 
-case_insensitive=
-unibad=
-no_symlinks=
-test_expect_success 'see what we expect' '
-
-	test_case=test_expect_success &&
-	test_unicode=test_expect_success &&
-	mkdir junk &&
-	echo good >junk/CamelCase &&
-	echo bad >junk/camelcase &&
-	if test "$(cat junk/CamelCase)" != good
-	then
-		test_case=test_expect_failure &&
-		case_insensitive=t
-	fi &&
-	rm -fr junk &&
-	mkdir junk &&
-	>junk/"$auml" &&
-	case "$(cd junk && echo *)" in
-	"$aumlcdiar")
-		test_unicode=test_expect_failure &&
-		unibad=t
-		;;
-	*)	;;
-	esac &&
-	rm -fr junk &&
-	{
-		ln -s x y 2> /dev/null &&
-		test -h y 2> /dev/null ||
-		no_symlinks=1 &&
-		rm -f y
-	}
-'
-
-test "$case_insensitive" &&
+if test_have_prereq CASE_INSENSITIVE_FS
+then
 	say "will test on a case insensitive filesystem"
-test "$unibad" &&
+	test_case=test_expect_failure
+else
+	test_case=test_expect_success
+fi
+
+if test_have_prereq UTF8_NFD_TO_NFC
+then
 	say "will test on a unicode corrupting filesystem"
-test "$no_symlinks" &&
+	test_unicode=test_expect_failure
+else
+	test_unicode=test_expect_success
+fi
+
+test_have_prereq SYMLINKS ||
 	say "will test on a filesystem lacking symbolic links"
 
-if test "$case_insensitive"
+if test_have_prereq CASE_INSENSITIVE_FS
 then
 test_expect_success "detection of case insensitive filesystem during repo init" '
 
@@ -62,18 +40,18 @@ test_expect_success "detection of case insensitive filesystem during repo init"
 '
 fi
 
-if test "$no_symlinks"
+if test_have_prereq SYMLINKS
 then
 test_expect_success "detection of filesystem w/o symlink support during repo init" '
 
-	v=$(git config --bool core.symlinks) &&
-	test "$v" = false
+	test_must_fail git config --bool core.symlinks ||
+	test "$(git config --bool core.symlinks)" = true
 '
 else
 test_expect_success "detection of filesystem w/o symlink support during repo init" '
 
-	test_must_fail git config --bool core.symlinks ||
-	test "$(git config --bool core.symlinks)" = true
+	v=$(git config --bool core.symlinks) &&
+	test "$v" = false
 '
 fi