'C-x p p C-x v L' to see a vc log in another project, and
'C-x p p C-x v d' to open vc-dir, etc.
All right, so we also want to support non-project commands. And you wanted
to use a common approach for both.
What if we handle them differently, though? For "project" commands (those
that internally call project-current) we can set one variable, and for the
rest -- alter default-directory. Then restore the previous value in
post-command.
The detection of "project commands" could work like this:
- Is it in one of the special maps? E.g. in project-prefix-map. Or maybe
it's in project-switch-commands.
- Does the function name start with 'project-'?
- Finally, for user-defined commands we could also introduce a property
'project-command-p', although the distinction between using
project-current-directory-override vs default-directory will not be
important for every such command, so maybe being this thorough is not too
important.