When trying to apply Petr's issue1888 patch to the 2.5 branch, I get a
message that darcs failed to read a certain patch. When I apply the
patch to the HEAD branch however, and then pull from the 2.5 branch, it
applies just fine.

The complete interaction showing the application to HEAD, the failure to
apply to the 2.5 branch and the successful pull:

reinier@adim:~/Sources/darcs-staging$ darcs apply
../darcs-reviews/resolve-issue1888_-fix-changes-__context_.dpatch 
Finished applying...
reinier@adim:~/Sources/darcs-staging$ cd ../branch-2.5
reinier@adim:~/Sources/branch-2.5$ darcs apply
../darcs-reviews/resolve-issue1888_-fix-changes-__context_.dpatch 
darcs: failed to read patch:
Wed Jul  7 20:02:10 CEST 2010  Ganesh Sittampalam <ganesh@earth.li>
  * standardize GHC options
Patch not stored in patch bundle:
Wed Jul  7 20:02:10 CEST 2010  Ganesh Sittampalam <ganesh@earth.li>
  * standardize GHC options
reinier@adim:~/Sources/branch-2.5$ darcs pull ../darcs-staging -p
'Resolve issue1888'
Thu Jul 29 20:51:43 CEST 2010  Petr Rockai <me@mornfall.net>
  * Resolve issue1888: fix changes --context.
Shall I pull this patch? (1/1)  [ynW...], or ? for more options: y
Backing up ./src/Darcs/Commands/Changes.lhs(-darcs-backup0)
We have conflicts in the following files:
./src/Darcs/Commands/Changes.lhs
Finished pulling and applying.

Attaching the context files of both repos as they were before the
command sequence in the above post.

Attachments

• 2.5-issue1901.ctx

As you can see, the branch-2.5 repository I was applying it to had local
modifications that conflicted. I can, however, reproduce it without
local modifications.

darcs 2.4.1 tells me:

darcs: Cannot apply this patch bundle, since we're missing:
Thu Jul 22 13:14:10 CEST 2010  Petr Rockai <me@mornfall.net>
  * Slightly fix context generation in Setup.

which is much better. So it's a regression.