Default getFile() to use the last accessed name in the FileEntry.

[klimek]

Summary

With modules we start accessing headers for the first time while
reading the module map, which often has very different paths from the include
scanning logic.

Using the name by which the file was accessed gets us one step closer to the
right solution, which is using a FileName abstraction that decouples the name
by which a file was accessed from the FileEntry.

[rsmith]

Seems reasonable as a short-term workaround. Can you add a test?

[klimek]

Added test and commited as r215541.

lib/Basic/FileManager.cpp

if (UFE.isValid()) { // Already have an entry with this inode, return it.
     // the VFS that the getDir() will have the virtual path, even if we found
     // the file by a 'real' path first. This is required in order to find a
     // module's structure when its headers/module map are mapped in the VFS.
     // We should remove this as soon as we can properly support a file having
     // multiple names.
     if (DirInfo != UFE.Dir && Data.IsVFSMapped)
       UFE.Dir = DirInfo;
 
+    // Always update the name to use the last name by which a file was accessed.
+    // FIXME: Neither this nor always using the first name is correct; we want
+    // to switch towards a design where we return a FileName object that
+    // encapsulates both the name by which the file was accessed and the
+    // corresponding FileEntry.
+    UFE.Name = Data.Name;
+
     return &UFE;
   }
 
   // Otherwise, we don't have this file yet, add it.
   UFE.Name    = Data.Name;
   UFE.Size = Data.Size;
   UFE.ModTime = Data.ModTime;
   UFE.Dir     = DirInfo;