dirstate: speed up read and write read: - single call to len(st) - fewer assignments for position tracking - don't split apart tuple from unpack - use a literal for the unpack spec write: - localize variables and functions - avoid copied function call - use % for string concatenation

% should fail
abort: path contains illegal component: .hg/00changelog.i
adding a/a
% should fail
abort: path 'b/b' traverses symbolic link 'b'
% should succeed
% should still fail - maybe
abort: path 'b/b' traverses symbolic link 'b'