mr: Lazy processing of repositories

[Svend Sorensen]

I'm using mr to manage the repositories for the various software that I
track. However, I don't want to check out all the repos by default. (The
list is getting long). I also don't want to make a modification to the
.mrconfig each time I want to check out a repo. (E.g. have 'skip = true'
on all repos, and remove the skip if I decide to check out a repo.)

I'm looking for a way to do lazy checkouts and updates. A lazy repo
would not be checked out unless I run a command to tell mr to check out
the repo. (Something like mr checkout foo.) After I force mr to check
out a lazy repo, mr would act on the repo for future mr runs.

One way to do this is to have skip check for the existence of a
different file for each repo. Creating the file would activate the repo.
Any ideas for a better approach?

Svend