BSP differences in 4.5.0 vs snapshots

[Paul Evans]

Hi,

Could anyone tell me if it's possible to (in theory) maintain a single
BSP that's compatible with both 4.5.0 and the current snapshot.
By (for instance) providing a configure.ac for the snapshot and
a  configure.in for 4.5.0 as well as doing some makefile.am tricks
to include things like "AUTOMAKE_OPTIONS = foreign 1.4"
only in the 4.5.0 build. (Ideally the bsp dir and the .cfg
file are both only links in each rtems tree)

Does this seems like too much to do? The easier option
might be to keep 2 sets of everything in conflict and maybe 
symlink each file back to what it really is before the build. (link
Makefile.am-for-snapshot --> Makefile.am for each
Makefile.am, the the same for configure.*  etc.)

I guess what I'm really hoping for is for someone wiser in 
build procedures and auto(conf|make) to tell me if the task
is more substantial than this or if this is doable. Or
if a bsp 'fork' (I use the term loosely)  is really what's 
order.

Thanks for any advice,

    -Paul