Applying Unix permission control at branch level.

[Sundar Bharadwaj]

Is there any way that Unix level user permissions can be set up at the
branch level.  This would enable controlling the Release branches so
that developers will not be able to commit files into this branch.  Only
a designated user (say the project integrator) will be able to update
the versions in this branch when absolutely necessary (say a critical
bug fix).

Thanks

Sundar