revset: parse alias declaration strictly by _parsealiasdecl Before this patch, alias declaration is parsed by string base operations: matching against "^([^(]+)\(([^)]+)\)$" and splitting by ",". This overlooks many syntax errors like below (see the previous patch introducing "_parsealiasdecl" for detail): - un-closed parenthesis causes being treated as "alias symbol" - symbol/function name aren't examined whether they are valid or not - invalid argument list causes unexpected argument names To parse alias declaration strictly, this patch replaces parsing implementation by "_parsealiasdecl". This patch tests only one typical declaration error case, because error detection itself is already tested in the doctest of "_parsealiasdecl". This also removes class property "args" and "error", because these are certainly initialized in "revsetalias.__init__".