would like grr list option

[bahamas10]

i'm thinking something simple like grr -l inside a repo would output something like this:

$ grr -l
OS-1
OS-2
TOOLS-1

given

$ git branch | grep ' grr-'
  grr-OS-1
  grr-OS-2
  grr-TOOLS-1

So then I could do something like

$ grr -D OS-1

or even

$ grr -l | xargs -n1 grr -D