revlog.revision(): minor cleanup
Rename some variables, making the name more obvious (in particular "cache" was
actually two different variable.
Move code around, moving the index preloading before the deltachain computation,
without that index preloading was useless (everything was read in deltachain).
% convert while testing all possible outputs
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
% check tags are in UTF-8
'221c3fdaf24df5f14c0a64c597581e2eacfb47bb branch\xc3\xa9e\n'
'7a40952c2db29cf00d9e31df3749e98d8a4bdcbf branch\xc3\xa9\n'