This function returns the current edit "id". The edit id is a number which gets incremented for each edit operation performed on the document. Command scripts can use this number to determine if the document was changed between two alias or user-defined function calls. The doc argument specifies the identifier of the document tree to query. If omitted or 0, the current document is used. If the flags argument is set and has a value of 1, then the function returns the edit id for the last structural change to doc.