tests: add a few tests involving --collapse and rebase.singletransaction=1 I'm about to change the rebase code quite a bit and this was poorly tested. Differential Revision: https://phab.mercurial-scm.org/D2757

tests: simplify test-rebase-transaction.t The file was extracted from test-rebase-base.t in 8cef8f7d51d0 (test-rebase-base: clarify it is about the "--base" flag, 2017-10-05). This patch follows up that and clarifies the new file's purpose and simplifies it a bit. Differential Revision: https://phab.mercurial-scm.org/D2756

hgweb: parse and store HTTP request headers WSGI transmits HTTP request headers as HTTP_* environment variables. We teach our parser about these and hook up a dict-like data structure that supports case insensitive header manipulation. Differential Revision: https://phab.mercurial-scm.org/D2742

wireprotoserver: remove broken optimization for non-httplib client There was an experimental non-httplib client in core for several years. It was removed a week or so ago. We kept the optimization for this client in the server code. I'm not sure if that was intended or not. But it doesn't matter: the code was wrong. Because the code was accessing a WSGI environment dict, it needed to access the HTTP_X_HGHTTP2 key to actually read the HTTP header. So the code deleted by this commit wasn't actually doing anything meaningful. Doh. Differential Revision: https://phab.mercurial-scm.org/D2741