revlog: abstract out index entry packing This lets us remove most of the remaining v0/v1 logic from revlog

revlog: simplify revlog.__init__ - move stat into io helper - get rid of self.defversion and self.indexstat - fold _load into __init__

revlog: mark cache private

revlog: pull chunkcache back into revlog

revlog: change _inline from a function to a variable

revlog: simplify addrevision - remove unused defaults for p1, p2, and text - reduce some if/else - use better variable names - remove some extra variables - remove some obsolete corner tests - simply first entry handling for revlogng - simply inline vs outofline writeout

revlog: some codingstyle cleanups

revlog: add a magic null revision to our index We expand our index by one entry so that index[nullrev] points to a unique entry, the null revision. This naturally eliminates numerous extra tests in the performance-sensitive index access functions, most of which are now trivial again. Adding new entries is now done with insert(-1, e) rather than append(e).

revlog: change accesses to index entry elements to use positive offsets

revlog: parse revlogv0 indexes into v1 internally This lets us eliminate lots of special case code in our performance-sensitive index accessors.