revlog: define the actual index and datafile at loading time
This is just code movement, to make the code closer to where we actually use it
and where it will be defined in the future.
Differential Revision: https://phab.mercurial-scm.org/D10594
BasedOnStyle: LLVM
IndentWidth: 8
UseTab: ForIndentation
BreakBeforeBraces: Linux
AllowShortIfStatementsOnASingleLine: false
IndentCaseLabels: false
AllowShortBlocksOnASingleLine: false
AllowShortFunctionsOnASingleLine: false
IncludeCategories:
- Regex: '^<'
Priority: 1
- Regex: '^"'
Priority: 2