Although the underlying software of 'rebuild' allows specification of a sequence of '-refs <branch>' indicating the search order of alternate branches to use during git repo recovery, the forward facing 'rebuild' command does not include them.
A trivial approach was taken in order to test feasibility of user specification using buildbot's interface. In the BB web interface, the user specifies both the parameter name (ref) and the parameter value (the blank separated strings of branches to use).
This was then massaged by the buildbot interface to provide the following string to 'rebuild':
During feasibility testing, 'rebuild' didn't accept any input parameters so a simple
sufficed to capture the refs and then use them via: