hgweb: inline caching() and port to modern mechanisms
We only had one consumer of this simple function. While it could be
a generic function, let's not over abstract the code.
As part of inlining, we port it off wsgirequest, fix some Python 3
issues, and set a response header on our new response object so it
is ready once we start using it to send responses.
Differential Revision: https://phab.mercurial-scm.org/D2785
Mercurial
=========
Mercurial is a fast, easy to use, distributed revision control tool
for software developers.
Basic install::
$ make # see install targets
$ make install # do a system-wide install
$ hg debuginstall # sanity-check setup
$ hg # see help
Running without installing::
$ make local # build for inplace usage
$ ./hg --version # should show the latest version
See https://mercurial-scm.org/ for detailed installation
instructions, platform-specific notes, and Mercurial user information.