Unlike posthooks for other commands, the posthooks for `darcs record` and 
`darcs amend-record` cannot access the environment variable DARCS_PATCHES.

I'd like the posthook for `darcs record` to receive the same DARCS_PATCHES 
variable that a posthook for a corresponding pull, push, send or apply 
receives.

I'd like the posthook for `darcs amend-record` to receive a meaningful 
DARCS_PATCHES variable.

I will implement tests and an implementation for this issue.

The following patch sent by Sebastian Fischer <mail@sebfisch.de> updated issue issue2312 with
status=resolved;resolvedin=2.10.0 HEAD

* resolve issue2312: posthooks for 'record' and 'amend-record' should receive DARCS_PATCHES 
Ignore-this: 8cd06d851c072ac1a7f2879490fd59b9

I have extended the 'record' and 'amend-record' commands to supply the
environment variable DARCS_PATCHES to posthooks.

The contents of DARCS_PATCHES is computed and provided by a new
function `Darcs.UI.Commands.Util.setChangesEnvAfter` that is used to
wrap the 'record' and 'amend-record' commands.

This function reads the repository before and after the executed
command. It uses the existing function
`Darcs.Patch.Depends.findCommonWithThem` to compute the changes made
by the command and `Darcs.UI.Commands.setEnvDarcsPatches` to provide
them to posthooks.