hgweb: cast bytearray to bytes PEP-3333 seems to indicate that bytes is the only allowed type that can be used to express the output of a WSGI application. And some WSGI environments seem to enforce this (mod_wsgi does). This commit universally casts bytearray instances to bytes to appease the WSGI specification. I found this because wireprotov2 is emitting bytearray instances. I'd like to keep things that way because the way it builds a data structure, bytearray is more efficient. I'd rather keep the low-level code efficient (and using bytearray) and cast at the edges than impose a performance penalty on code that may run outside WSGI contexts.

help: unjumble the list of default config values for `internals.config`

ui: hide fin/fout/ferr attributes behind @property functions This allows keeping references to fout/ferr/fin which are updated when these properties are changed. See the next patch.

ui: label prompt and echo messages I'm going to add a dedicated command-server channel for status messages, which carries metadata alongside a message text. 'ui.*' label provides a hint how message text should be processed.

ui: add inner function to select write destination I'm going to add a config knob to redirect any status messages to stderr. This function helps to switch underlying file objects. # no-check-commit because of existing write_err() function

ui: remove _write() and _write_err() functions

ui: move pre/post processes from low-level write()s to _writenobuf() This helps adding a dedicated stream for status/error messages. I don't want to add _write*() function per stream.

ui: pass in file object to _writenobuf() See the subsequent patches for why. The "if" block in _writenobuf() will be removed soon.