Use merge/.. tag as base for generating patches

This locally-made tag is used to mark the merge of the upstream tag
into our branch. It avoids generating patches for upstream commits
that are in the previous upstream tag but not in the current one.

Change-Id: If7407657ee9185757eb193758a10011da5ea0e5b
Improve handling of reference repos

Change-Id: If195d5c2367fe286118454ff0ccf7c4c5ebc383f
Handle submodules in source repo

Needed for mono 3

Change-Id: I66d81cfd5d331f117eb8a68160698c796bee82b0
Change mono build dependencies

Newer system monos no longer include mono 2.0 by default, but
bootstrapping the mono build needs it. Depend on libmono-cil-dev
instead of mono-runtime to ensure mono 2.0 is available.

Change-Id: Ic9a4b2ac181d4054c254dab81284fe541bffd3d6
Update debian changelog for mono-sil 3.4.0-1

Change-Id: I264f55317ca3d9f5b7533a8cc9b8da9d9b96c2d3
Update debian changelog for mono-sil 3.4.0-2

Change-Id: Ib6be24ca90665621553cd4f236f45bdfee8641bb