[System.IO] Directory.Exists() now resolves the full path first. Fixes #60267

In Unix, assume our current directory contains:
`test`, a directory
`test/test2`, another directory
`test/test2/test_file`, a file
`test3`, a symbolic link pointing to `test/test2`

Then the path "test3/../test3" has two interpretations depending on the processor:

* The OS (the `lstat` syscall, `ls`, etc.) will find it invalid (as it evaluates to: enter `test/test2`, go up one level, try to enter `test3` which is another level down
* We (.NET, at least CoreCLR) should find it valid (enter `test3`, go up one level, enter `test3`).

This ensures that for Directory.Exists, we process the path `..`'s on the .NET level before passing it for native processing.

1 files changed, 10 insertions, 3 deletions

diff --git a/mcs/class/corlib/System.IO/Directory.cs b/mcs/class/corlib/System.IO/Directory.cs
index cab5f3ee047..755e8510816 100644
--- a/mcs/class/corlib/System.IO/Directory.cs
+++ b/mcs/class/corlib/System.IO/Directory.cs
@@ -195,11 +195,18 @@ namespace System.IO
 			// on Moonlight this does not throw but returns false
 			if (!SecurityManager.CheckElevatedPermissions ())
 				return false;
-				
+
+			string full_path;
+			try {
+				full_path = Path.GetFullPath (path);
+			} catch {
+				return false;
+			}
+
 			MonoIOError error;
 			bool exists;
-			
-			exists = MonoIO.ExistsDirectory (path, out error);
+
+			exists = MonoIO.ExistsDirectory (full_path, out error);
 			/* This should not throw exceptions */
 			return exists;
 		}