RFC: migrating to git

[Claus Reinke]

> We can't even do this reliably with darcs.  Several times I've tried to 
> unpull one of Simon's patches to work around a bug, and the dependencies 
> end up being more than just the textual dependencies.  Then I have to 
> fall back to unpulling by date, which is what git would do.  And then 
> sometimes there's the separate problem that you have to retreat the 
> library repos too, and there you have to unpull by date and some 
> guesswork too.

Perhaps it is possible to take the guesswork out of this
latter problem? For all the repos to be linked, maintain 
a single file "patch-history.txt", add a posthook to all
repos so that every commit will be logged as a line in 
patch-history.txt:

    repo-id : patch-id : short commit message, or other greppable info

Then, if you have a patch id in the GHC repo, you just have
to search backward from that id in patch-history.txt until
you have matching last-patch ids for the other repos. That 
search (and darcs-all (un-)pulling up to the patch ids for 
all repos) could probably be scripted, so it would become 
a single command (input: repo-id/patch-id for a patch in
one of the repos; output: list of repo-ids/patch-ids identifying 
a consistent set of repo states).

Could that be made to work?

Claus