darcs repair complains when there is no pristine.hashed directory, while 
it should just recreate it!

Darcs.Commands.Repair uses the function Darcs.Repository.amInRepository 
as a prerequisite. Then the calls are:

Darcs.Repository.amInRepository
Darcs.Repository.maybeIdentifyRepository
 check if _darcs exists (doesDirectoryExists)
 if ok, check if it can handle _darcs/formats  (identifyRepoFormat)
 if ok, identify pristine tree
    -> Darcs.Repository.Pristine.identifyPristine
        if no pristine tree in any format, display: "Pristine tree does 
not exist"

Bad solution: remove identifyPristine completely, since commands other 
than repair need to use that pristine tree to work!

So I suggest that the prerequisite of "darcs repair" is not 
amInRepository, but amInRepairableRepository, which will not make any 
pristine tree test, and aim at rebuilding a pristine.hashed tree.

The following patch sent by Guillaume Hoffmann <guillaumh@gmail.com> updated issue issue1977 with
status=resolved;resolvedin=2.8.0 HEAD

* resolve issue1977 by considering more repositories as being NoPristine 
Ignore-this: 41987c65face6b464951509e4eeda1f2