tests: make custom templates that use {whyunstable} terser
These templates demonstrate that {whyunstable} is fully template-friendly, but
they don't need to produce such long lines of output.
makefile: add Ubuntu Bionic docker targets (.deb and ppa)
Bionic Beaver is an LTS release, supported until 2023-04.
makefile: reformat .PHONY targets
The list of make targets is likely to evolve over time. This reformats
streamlines future patches.
makefile: mkdir is not needed on templatized docker builds
This imitates
e63dfbbdbd07 and is a small addition to
231690dba9b4 and
5c1283713293
hgweb: convert _siblings to a factory function of mappinggenerator
IIUC, only reason it was a class is to make the generator restartable,
which is now served by the mappinggenerator.
hgweb: extract a generator function of _siblings class
_siblings will be converted to a plain function.
hgweb: make revnav.gen() simply build a list of mappings by one pass
There was actually no lazy stuff.