Continuous Merging For GDC and LDC?

[dsimcha]

How does the merging process for new Phobos/druntime/DMD front ends work 
w.r.t. GDC and LDC?  To what extent is it automated?  If it's mostly 
automated except when things go wrong (or could be made so), we should 
set up a server somewhere (maybe on one of the DMD tester boxes that's 
underworked, if there is one) that automatically merges every commit to 
druntime/phobos/dmd and tests it.

It seems to take agonizingly long after every DMD release for LDC and 
GDC to get caught up, which makes sense only if the merges are being 
done by hand or changes are made to low-level stuff (certain parts of 
druntime, the glue layer of the compiler, etc.).  Furthermore, such 
continuous merging might encourage DMD/Phobos/druntime devs to do things 
in a more LDC/GDC-friendly way and would make trunk revisions of 
Phobos/druntime/dmd in between releases available to GDC/LDC users.