Bug 305004 The PathVariableSelectionDialog should not use 'Extend' to build path variable arguments
The PathVariableSelectionDialog should not use 'Extend' to build path variable arguments, since this is used already to build a path, which could be used to build a path starting off an argumented path variable.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/ide/dialogs/PathVariableSelectionDialog.java
* @param extensionFile file selected to extend the variable.
     */
    private void setExtensionResult(
            PathVariablesGroup.PathVariableElement variable, IFileStore extensionFile) {
        IPath extensionPath = new Path(extensionFile.toString());
		IPath selectionPath = variable.path;
		if (currentResource != null)
			selectionPath = URIUtil.toPath(currentResource.getPathVariableManager().resolveURI(URIUtil.toURI(selectionPath)));
		int matchCount = extensionPath.matchingFirstSegments(selectionPath);
        IPath resultPath = new Path(variable.name);
        extensionPath = extensionPath.removeFirstSegments(matchCount);
        resultPath = resultPath.append(extensionPath);
		setSelectionResult(new String[] { resultPath.toPortableString() });
    }
    /**
     * Updates the enabled state of the Extend button based on the 
     * current variable selection.
     */
    private void updateExtendButtonState() {
        PathVariablesGroup.PathVariableElement[] selection = pathVariablesGroup
                .getSelection();
        Button extendButton = getButton(EXTEND_ID);
        if (extendButton == null) {
			return;
		}
        if (selection.length == 1) {
			IPath selectionPath = selection[0].path;
			if (currentResource != null)
				selectionPath = URIUtil.toPath(currentResource.getPathVariableManager().resolveURI(URIUtil.toURI(selectionPath)));
			IFileInfo info = IDEResourceInfoUtils.getFileInfo(selectionPath);