Introduce llvm::sys::path::home_directory.

This will be used by the line editor library to derive a default path to
the history file.

Differential Revision: http://llvm-reviews.chandlerc.com/D2199

llvm-svn: 200594
diff --git a/llvm/unittests/Support/Path.cpp b/llvm/unittests/Support/Path.cpp
index f71c7c5..197e1c2 100644
--- a/llvm/unittests/Support/Path.cpp
+++ b/llvm/unittests/Support/Path.cpp
@@ -210,6 +210,19 @@
 }
 #endif // LLVM_ON_WIN32
 
+TEST(Support, HomeDirectory) {
+#ifdef LLVM_ON_UNIX
+  // This test only makes sense on Unix if $HOME is set.
+  if (::getenv("HOME")) {
+#endif
+    SmallString<128> HomeDir;
+    EXPECT_TRUE(path::home_directory(HomeDir));
+    EXPECT_FALSE(HomeDir.empty());
+#ifdef LLVM_ON_UNIX
+  }
+#endif
+}
+
 class FileSystemTest : public testing::Test {
 protected:
   /// Unique temporary directory in which all created filesystem entities must