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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200594 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Support/Unix/Path.inc

@@ -797,5 +797,20 @@ error_code openFileForWrite(const Twine &Name, int &ResultFD,
 }
 
 } // end namespace fs
+
+namespace path {
+
+bool home_directory(SmallVectorImpl<char> &result) {
+  if (char *RequestedDir = getenv("HOME")) {
+    result.clear();
+    result.append(RequestedDir, RequestedDir + strlen(RequestedDir));
+    return true;
+  }
+
+  return false;
+}
+
+} // end namespace path
+
 } // end namespace sys
 } // end namespace llvm