fix: refactor getrevstofix() to define revisions first, then validate them
This refactoring makes it easier to add a new way of specifying
revisions (I'm about to add a `--source`, which adds the specified
revisions and their descendants).
Differential Revision: https://phab.mercurial-scm.org/D8285
BasedOnStyle: LLVM
IndentWidth: 8
UseTab: ForIndentation
BreakBeforeBraces: Linux
AllowShortIfStatementsOnASingleLine: false
IndentCaseLabels: false
AllowShortBlocksOnASingleLine: false
AllowShortFunctionsOnASingleLine: false
IncludeCategories:
- Regex: '^<'
Priority: 1
- Regex: '^"'
Priority: 2