Add tests for git check-ref-format

The "git check-ref-format" command is a basic command various
porcelains rely on.  Test its functionality to make sure it does
not unintentionally change.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t1402-check-ref-format.sh

@@ -0,0 +1,44 @@
+#!/bin/sh
+
+test_description='Test git check-ref-format'
+
+. ./test-lib.sh
+
+valid_ref() {
+	test_expect_success "ref name '$1' is valid" \
+		"git check-ref-format '$1'"
+}
+invalid_ref() {
+	test_expect_success "ref name '$1' is not valid" \
+		"test_must_fail git check-ref-format '$1'"
+}
+
+valid_ref 'heads/foo'
+invalid_ref 'foo'
+valid_ref 'foo/bar/baz'
+valid_ref 'refs///heads/foo'
+invalid_ref 'heads/foo/'
+invalid_ref './foo'
+invalid_ref '.refs/foo'
+invalid_ref 'heads/foo..bar'
+invalid_ref 'heads/foo?bar'
+valid_ref 'foo./bar'
+invalid_ref 'heads/foo.lock'
+valid_ref 'heads/foo@bar'
+invalid_ref 'heads/v@{ation'
+invalid_ref 'heads/foo\bar'
+
+test_expect_success "check-ref-format --branch @{-1}" '
+	T=$(git write-tree) &&
+	sha1=$(echo A | git commit-tree $T) &&
+	git update-ref refs/heads/master $sha1 &&
+	git update-ref refs/remotes/origin/master $sha1
+	git checkout master &&
+	git checkout origin/master &&
+	git checkout master &&
+	refname=$(git check-ref-format --branch @{-1}) &&
+	test "$refname" = "$sha1" &&
+	refname2=$(git check-ref-format --branch @{-2}) &&
+	test "$refname2" = master'
+
+test_done