cat: use with statement to close output file

cat: stop using makefileobj() Prepares for porting to the formatter API. We won't be able to utilize the abstraction provided by makefilename() because formatter must be instantiated per file.

formatter: add nullformatter This can be used as a placeholder variable.

formatter: add helper to create a formatter optionally backed by file To make things simple, openformatter() and maybereopen() have no support for a plain object API. Callers must use the "with" statement. Unlike cmdutil.makefileobj(), append mode ('ab') isn't supported by these functions. This is because JSON output can't be simply concatenated. Perhaps cmdutil.export() will have to build a {filename: [revs...]} map first and write revs per file.

formatter: add option to redirect output to file object Commands like 'export' have --output=OUTFILESPEC option, so we need a way to write formatter output optionally to a file.

merge with i18n

i18n-pt_BR: synchronized with a0e46f6b248b

zsh_completion: install as _hg not hg The contrib/zsh_completion file itself says to name it _hg. With a name like `hg`, if the user has a line like `autoload ${^fpath}/*(N-.:t)` in their zshrc, it will create a shell function named `hg` that will hide the actual hg command and make hg unusable. Separately from that though, the underscore prefix makes it actually work. The zsh man page states: The convention for autoloaded functions used in completion is that they start with an underscore This does not seem to just be a "convention", though. With the ill-advised line removed from my zshrc and the file named `/usr/local/share/zsh/site-functions/hg` (without the underscore), these completions did not seem to get loaded and the ones from the zsh installation were loaded instead. If I renamed them to be `/usr/local/share/zsh/site-functions/_hg`, however, they were loaded. I manually tested the above statement by starting a new zsh instance with the file in `/usr/local/share/zsh/site-functions` with the following names: - As `hg`, `which _hg_labels` did not show anything - As `_hg`, `which _hg_labels` showed the expected function.