I don't think this is a regression, but the longest time, I could have sworn
there was some kind of problem with partial repositories and checkpoints.

I think this /might/ illustrate it:

darcs get http://modeemi.fi/~tuomov/repos/riot riot-full
darcs get riot-full

darcs get --partial http://modeemi.fi/~tuomov/repos/riot riot-partial
# this does not work
darcs get riot-partial p1
# nor does this
darcs get --partial riot-partial p2

I'm adding Ian to this because I think we had a discussion about this once...
although in the previous discussion, Ian managed to convince me that everything
was working perfectly after all.

Could this be related to some sort of bug in an older darcs maybe?

Thorkil, please feel free to mark this as wont-fix... I just thought it would be
useful to have some sort of placeholder in case we get other such complaints
about partial repositories.

Perhaps the answer we should start giving people is "upgrade to the hashed
format and use --lazy instead"