Index: AbstractIdeaMojo.java
===================================================================
--- AbstractIdeaMojo.java	(revision 564066)
+++ AbstractIdeaMojo.java	(working copy)
@@ -40,8 +40,8 @@
 import org.apache.maven.project.MavenProject;
 import org.apache.maven.project.ProjectBuildingException;
 import org.apache.maven.project.artifact.InvalidDependencyVersionException;
+import org.codehaus.plexus.util.xml.Xpp3Dom;
 import org.codehaus.plexus.util.StringUtils;
-import org.codehaus.plexus.util.xml.Xpp3Dom;
 import org.dom4j.Document;
 import org.dom4j.DocumentException;
 import org.dom4j.Element;
@@ -50,14 +50,7 @@
 
 import java.io.File;
 import java.io.IOException;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.HashSet;
-import java.util.Iterator;
-import java.util.List;
-import java.util.Map;
-import java.util.Set;
+import java.util.*;
 
 /**
  * @author Edwin Punzalan
@@ -211,21 +204,56 @@
      */
     protected String toRelative( File basedir, String absolutePath )
     {
-        String relative;
+        // Get character arrays for the paths and find the equal prefixes.
+        final char[] basedirChars = StringUtils.replace(basedir.getAbsolutePath(), "\\", "/").toCharArray();
+        final char[] absolutePathChars = StringUtils.replace(absolutePath, "\\", "/").toCharArray();
+        int firstUnequalCharPos = 0;
+        for (; firstUnequalCharPos < Math.min(basedirChars.length, absolutePathChars.length); ++firstUnequalCharPos)
+        {
+            if (basedirChars[firstUnequalCharPos] != absolutePathChars[firstUnequalCharPos])
+            {
+                break;
+            }
+        }
 
-        if ( absolutePath.startsWith( basedir.getAbsolutePath() )
-            && absolutePath.length() > basedir.getAbsolutePath().length() )
+        // Build a relative path if the paths share an ancestor directory.
+        final String relativePath;
+        if (0 == firstUnequalCharPos)
         {
-            relative = absolutePath.substring( basedir.getAbsolutePath().length() + 1 );
+            relativePath = absolutePath;
         }
         else
         {
-            relative = absolutePath;
+            // If basedir and absolutePath are both subdirectories of a common parent, then we will have to ".." to
+            // that parent and concatenate the unequal part of absolutePath.
+            final StringBuffer relativePathBuffer = new StringBuffer();
+            if (firstUnequalCharPos < basedirChars.length || '/' != absolutePathChars[firstUnequalCharPos])
+            {
+                for (int i = firstUnequalCharPos; i < basedirChars.length; ++i)
+                {
+                    if ('/' == basedirChars[i] && i < basedirChars.length - 1)
+                    {
+                        relativePathBuffer.append("../");
+                    }
+                }
+                relativePathBuffer.append("../");
+            }
+
+            // We've now appended enough ".." elements to get us to the common directory. Now append the unequal
+            // part of absolutePath, from the last separator character in the equal part.
+            int lastSeparatorIndex = firstUnequalCharPos;
+            for (; lastSeparatorIndex >= 0; --lastSeparatorIndex)
+            {
+                if ('/' == absolutePathChars[lastSeparatorIndex])
+                {
+                    break;
+                }
+            }
+            relativePathBuffer.append(absolutePathChars, lastSeparatorIndex + 1, absolutePathChars.length -
+                    lastSeparatorIndex - 1);
+            relativePath = relativePathBuffer.toString();
         }
-
-        relative = StringUtils.replace( relative, "\\", "/" );
-
-        return relative;
+        return relativePath;
     }
 
     /**