revlog: add a function to build index entry tuple Keeping index entry as tuple make sense for performance reason, however it does not means we need to manually build that tuple for all piece of python code that are not performance critical. So we add a nice function responsible to build the tuple using argument using explicit keyword argument. Differential Revision: https://phab.mercurial-scm.org/D10793

revlog: move `offset_type` to `revlogutils` This multiple module are using this so it make sense to move it at the utility level. Differential Revision: https://phab.mercurial-scm.org/D10792

revlog: move entry documentation alongside new related constants Accessing individual index-entry element is usually done using integer directly. This is presumably for "performance reasons". However as the index entry gain more and more element it seems useful to get the option to use symbolic constant to access item, for both clarify and versatility. We will probably keep using integer for performance critical path, but less critical code may start using them now that they are declared. Differential Revision: https://phab.mercurial-scm.org/D10791