[hyena] Paths: add new SwitchRoot method

[AndrÃs Aragoneses <aaragoneses src gnome org>]

commit a2f18e52e618bc7aa3f6ad3aa66072acbe89f9e2
Author: Andres G. Aragoneses <knocte gmail com>
Date:   Sun Jan 13 02:01:04 2013 +0000

    Paths: add new SwitchRoot method
    
    This method will be used to switch the mount point of a path with a
    different one. Example:
    
     SwitchRoot ("/foo/bar/", "/foo", "/baz") == "/baz/bar"
    
    First usage of it will be in Banshee, in an upcoming
    patch for N95 playlists support (bgo#661507).

 Hyena/Hyena/Paths.cs |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)
---
diff --git a/Hyena/Hyena/Paths.cs b/Hyena/Hyena/Paths.cs
index c2368dd..1fe3472 100644
--- a/Hyena/Hyena/Paths.cs
+++ b/Hyena/Hyena/Paths.cs
@@ -116,6 +116,14 @@ namespace Hyena
             return path.Split (UnixSeparator);
         }
 
+        public static string SwitchRoot (string path, string mountPoint, string rootPath)
+        {
+            if (!path.StartsWith (mountPoint)) {
+                throw new ArgumentException ("mountPoint must be contained in first part of the path");
+            }
+            return path.Replace (mountPoint, rootPath);
+        }
+
         public static string MakePathRelative (string path, string to)
         {
             if (String.IsNullOrEmpty (path) || String.IsNullOrEmpty (to)) {