Allow auto-merging specific branch/branches

Customers might use a set of branches named as follows:

Development branch:
master

Release Branches:
release/aaa.1
release/aaa.2
release/aaa.3
release/bbb.1
release/bbb.2
release/bbb.3
release/ccc.1
release/ccc.2
release/ccc.3

Essentially - families of releases (aaa, bbb, ccc), with numbered iterations.

When auto-merge feature is turned on in Stash on this repo, a pull request to any numbered iteration of a given family attempts to auto-merge across all subsequent iterations of that release family. However, the auto-merge utility also auto-merges down to the Development branch automatically, and this is something they might like to control the merging on manually, and currently there is no way of turning off the Development branch auto-merge in the built-in Stash functionality.

To clarify - the automerge currently merges (using the branches above) in the following flow:
bbb.0 -> bbb.1 -> bbb.2 -> master

They might like it to automatically flow like:
bbb.0 -> bbb.1 -> bbb.2

With a subsequent manual merge (via pull request) from bbb.2 -> master.