Option parsing: recognize the special -- token

Everything that comes after -- should be treated as a filename. This
enables passing in filenames that would otherwise be conflated with
command-line options.

This is especially important for clang-cl which supports options
starting with /, which are easily conflatable with Unix-style
path names.

Differential Revision: http://llvm-reviews.chandlerc.com/D1274

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187675 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/unittests/Option/OptionParsingTest.cpp b/unittests/Option/OptionParsingTest.cpp
index 2a5a5a9..5a76d65 100644
--- a/unittests/Option/OptionParsingTest.cpp
+++ b/unittests/Option/OptionParsingTest.cpp
@@ -156,3 +156,16 @@
   EXPECT_EQ(AL->getAllArgValues(OPT_B)[0], "foo");
   EXPECT_EQ(AL->getAllArgValues(OPT_B)[1], "bar");
 }
+
+TEST(Option, DashDash) {
+  TestOptTable T;
+  unsigned MAI, MAC;
+
+  const char *MyArgs[] = { "-A", "--", "-B", "--" };
+  OwningPtr<InputArgList> AL(T.ParseArgs(MyArgs, array_endof(MyArgs), MAI, MAC));
+  EXPECT_TRUE(AL->hasArg(OPT_A));
+  EXPECT_FALSE(AL->hasArg(OPT_B));
+  EXPECT_EQ(AL->getAllArgValues(OPT_INPUT).size(), 2U);
+  EXPECT_EQ(AL->getAllArgValues(OPT_INPUT)[0], "-B");
+  EXPECT_EQ(AL->getAllArgValues(OPT_INPUT)[1], "--");
+}