checkheads: drop now unused filtering of 'unsyncedheads' Now that unsynced heads are no longer in the function inputs or returns, we can simplify the code a bit.

checkheads: clarify that we no longer touch the head unknown locally Since c6cb21ddf74a, heads unknown locally no longer get any post processing from obsolescence markers. We clarify this fact by only feeding the list of locally known new heads to the function. This simplification of the input will help moving that post-processing earlier in the function.

headssummary: ensure all returned lists are sorted This is a simple step that will help to keep a stable output in coming refactoring.

discovery: also use lists for the returns of '_oldheadssummary' The '_headssummary' function is documenting and using list objects in its return. We now use them in _oldheadssummary too for consistency. This does not affect any usages of these values.

test: add a push race case where the updated head is obsoleted This is the mirror of the previously added case. We check the case where the racing-push obsoletes a head while the raced-push updates that same head.

test: add a push race case where obsoleted head is updated We check the case where the raced-push obsoletes a head while the racing-push updates that same head.

keepalive: set buffering=True to do more efficient reads of headers Support for buffering was added to python in d09d6fe31b61, first released with python2.7. Without this, the entirety of the response headers is read byte-by-byte (it does more efficient reads when it gets to the non-header part of the response).

keepalive: pass the correct arguments to HTTPResponse python2.7's httplib.HTTPResponse takes the arguments in the following order: sock, debuglevel, strict, method, buffering This was previously passing them in as positional and skipped strict, so we set strict=method. I'm explicitly setting strict=True now to preserve the previous behavior that has been there since this file was created.