tests: conditionalize some output for Windows A couple of these were already present, but out of place.

test-pyflakes: use '/' when printing the files to check If paths are printed with '\', `xargs` sees the parts allsmooshedtogether, and pyflakes errors out.

tests: fix PYTHONPATH manipulation on Windows Without the semicolon separator and quotes, the variables ends up like this: c:\Users\Matt\projects\hg-evolve:c:\Users\Matt\projects\hg-evolve: c:\Users\Matt\projects\hg;c:\Users\Matt\projects\hg-evolve\tests; c:\Users\Matt\projects\hg\tests That in turn makes the local evolve code unreachable, and the system installed code is tested instead. I'm testing against `uname` instead of a trivial python script printing os.name because maybe one day tests will run on WSL.

exthelper: update documentation with some examples for using registrar aliases

exthelper: simplify the ability to register filesets Same mechanism as revsets earlier in this series.

exthelper: simplify the ability to register templates Same mechanism as revsets earlier in this series.

exthelper: simplify the ability to register revsets I think this is what Yuya and Boris agreed on.[1] This happens *after* the extsetup phase now (and after the _aftercallback notifications). But this is trivial, mergeable between exthelper instances, and doesn't need to have the extension name supplied when registering. [1] https://www.mercurial-scm.org/pipermail/mercurial-devel/2018-December/125888.html

exthelper: support the option argument when registering a command Largefiles uses this 5th argument with push and pull, so this will be tested in the next commit. I assume the reason for unrolling and reforming the tuple in each finalxxxsetup() is to validate that something proper was passed in when registering. But it's better to explode when decorating than during the delayed actual registration.