Set core.precomposeunicode to true on e.g. HFS+

When core.precomposeunicode was introduced in 76759c7,
it was set to false on a unicode decomposing file system like HFS+
to be compatible with older versions of Git.

The Mac OS users need to find out that this configuration exist
and change it manually from false to true.

A smoother workflow can be achieved,
so set core.precomposeunicode to true on a decomposing file system.

Signed-off-by: Torsten Bögershausen <tboegi@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

compat/precompose_utf8.c

@@ -48,11 +48,8 @@ void probe_utf8_pathname_composition(char *path, int len)
 	if (output_fd >= 0) {
 		close(output_fd);
 		strcpy(path + len, auml_nfd);
-		/* Indicate to the user, that we can configure it to true */
-		if (!access(path, R_OK))
-			git_config_set("core.precomposeunicode", "false");
-		/* To be backward compatible, set precomposed_unicode to 0 */
-		precomposed_unicode = 0;
+		precomposed_unicode = access(path, R_OK) ? 0 : 1;
+		git_config_set("core.precomposeunicode", precomposed_unicode ? "true" : "false");
 		strcpy(path + len, auml_nfc);
 		if (unlink(path))
 			die_errno(_("failed to unlink '%s'"), path);

t/t0050-filesystem.sh

@@ -91,6 +91,7 @@ test_expect_failure CASE_INSENSITIVE_FS 'add (with different case)' '
 test_expect_success "setup unicode normalization tests" '
 	test_create_repo unicode &&
 	cd unicode &&
+	git config core.precomposeunicode false &&
 	touch "$aumlcdiar" &&
 	git add "$aumlcdiar" &&
 	git commit -m initial &&

t/t3910-mac-os-precompose.sh

@@ -36,7 +36,7 @@ Alongc=$Alongc$AEligatu$AEligatu                     #254 Byte
 
 test_expect_success "detect if nfd needed" '
 	precomposeunicode=`git config core.precomposeunicode` &&
-	test "$precomposeunicode" = false &&
+	test "$precomposeunicode" = true &&
 	git config core.precomposeunicode true
 '
 test_expect_success "setup" '

t/t7400-submodule-basic.sh

@@ -958,7 +958,6 @@ test_expect_success 'submodule with UTF-8 name' '
 		git add sub &&
 		git commit -m "init sub"
 	) &&
-	test_config core.precomposeunicode true &&
 	git submodule add ./"$svname" &&
 	git submodule >&2 &&
 	test -n "$(git submodule | grep "$svname")"