[Gnu-arch-users] Generating *context* diffs out of changesets

[Emilio Lopes]

I'm considering using GNU Arch (tla) for tracking a large project which
currently uses CVS.  I only have read-only access to the CVS repository.

While I'll be keeping my local changes under Arch's control, the only
possibility for me to submit changes to the code base is through (plain
boring) patches.

Sometimes I choose to implement a feature in several independent steps.  A
simple example:

   - patch 40 implemented the first step

   - patch 41 was an update from CVS

   - patch 42 implement the second step of the new feature

Now I want to send a single *context* diff (generated with 'diff -c')
generated out of changesets 40 and 42, ignoring patch 41 of course.

How, if at all, can I accomplish this with tla?