t7610-mergetool: use test_config to isolate tests

Signed-off-by: David Aguilar <davvid@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: davvid

t/t7610-mergetool.sh

@@ -112,7 +112,7 @@ test_expect_success 'custom mergetool' '
 '
 
 test_expect_success 'mergetool crlf' '
-	git config core.autocrlf true &&
+	test_config core.autocrlf true &&
 	git checkout -b test2 branch1 &&
 	test_must_fail git merge master >/dev/null 2>&1 &&
 	( yes "" | git mergetool file1 >/dev/null 2>&1 ) &&
@@ -505,14 +505,12 @@ test_expect_success 'file with no base' '
 
 test_expect_success 'custom commands override built-ins' '
 	git checkout -b test14 branch1 &&
-	git config mergetool.defaults.cmd "cat \"\$REMOTE\" >\"\$MERGED\"" &&
-	git config mergetool.defaults.trustExitCode true &&
+	test_config mergetool.defaults.cmd "cat \"\$REMOTE\" >\"\$MERGED\"" &&
+	test_config mergetool.defaults.trustExitCode true &&
 	test_must_fail git merge master &&
 	git mergetool --no-prompt --tool defaults -- both &&
 	echo master both added >expected &&
 	test_cmp both expected &&
-	git config --unset mergetool.defaults.cmd &&
-	git config --unset mergetool.defaults.trustExitCode &&
 	git reset --hard master >/dev/null 2>&1
 '