py3: use .startswith() instead of bytes[0] bytes[0] returns the ascii value of character at 0 index. Differential Revision: https://phab.mercurial-scm.org/D3580

crecord: fallback to text mode if diffs are too big for curses mode crecord uses curses.newpad to create a region that we can then scroll around in by moving the main 'screen' as a veiwport into the (probably larger than the actual screen) pad. Internally, at least in ncurses, pads are implemented using windows, which have their dimensions limited to a certain size. Depending on compilation options for ncurses, this size might be pretty small: (signed) short, or it might be larger ((signed) int). crecord wants to have enough room to have all of the contents of the main area of the chunkselector in the pad; this means that the full size with everything expanded must be less than these (undocumented, afaict) limits. It's not easy to write tests for this because the limits are platform- and installation- dependent and undocumented / unqueryable, as far as I can tell. Differential Revision: https://phab.mercurial-scm.org/D3577

narrow: filter copies in core Differential Revision: https://phab.mercurial-scm.org/D3576