code: func (c handlerContext) childCtx(fi *fileInfo) *handlerContext {
  	if c.currentPage == nil {
  		panic("Need a Page to create a child context")
  	}
  
  	c.target = strings.TrimPrefix(fi.Path(), c.bundle.fi.Dir())
  	c.source = fi
  
  	c.doNotAddToSiteCollections = c.bundle != nil && c.bundle.tp != bundleBranch
  
  	c.bundle = nil
  
  	c.parentPage = c.currentPage
  	c.currentPage = nil
  
  	return &c
  }
docs: // Create a copy with the current context as its parent.