Added doc/branches.md: List of active development branches

The file serves three purposes:

- Help users find out what branches exist.
- Help developers advertise their branches.
- Help to automatically sync branches onto the SnabbCo repository.

Github provides an automatic summary of the current state of all these
branches on the [SnabbCo/snabbswitch
branches](/~https://github.com/SnabbCo/snabbswitch/branches/all) page.

This is intended to help new long-lived branches to develop features
and synchronize with master and other branches over time.

src/doc/branches.md

@@ -0,0 +1,42 @@
+## Snabb Switch development branches
+
+The branches listed below are automatically synchronized with the
+SnabbCo account on Github. Users typically get all of these branches
+together by pulling from the main repository.
+
+The current state of each branch with respect to master is visible here:
+
+- /~https://github.com/SnabbCo/snabbswitch/branches/all
+
+#### master
+
+    BRANCH: master git://github.com/lukego/snabbswitch
+    Synchronization point with changes recommended for all users.
+
+    - Makes monthly releases.
+    - Changes are gated by the SnabbBot CI
+    - Currently Linux/x86-64 with GNU tools (more in the future)
+
+    Maintainer: Luke Gorrie <luke@snabb.co> and Max Rottenkolber <max@mr.gy>
+
+#### documenation-fixups
+
+    BRANCH: documentation-fixups git://github.com/eugeneia/snabbswitch
+    Documentation fixes and improvements.
+
+    Maintainer: Max Rottenkolber <max@mr.gy>
+
+#### nfv
+
+    BRANCH: nfv git://github.com/lukego/snabbswitch
+    snabbnfv application development branch.
+
+    Maintainer: Luke Gorrie <luke@snabb.co>
+
+#### vpn
+
+    BRANCH: vpn git://github.com/alexandergall/snabbswitch
+    VPN application development branch.
+
+    Maintainer: Alexander Gall <gall@switch.ch>
+