cmd/go: make vcs command actually gather output
cmd/go: make vcs command actually gather output

R=rsc, bradfitz
CC=golang-dev
http://codereview.appspot.com/5577062

rflanagan/reginaldflanagan-project1,rflanagan/reginaldflanagan-project1,rflanagan/reginaldflanagan-project1,rdp/rogerpack2005-golang,Triskite/willstone-goclone,glycerine/jeaten-go-arrayof-structof,d0f/go-zh,glycerine/jeaten-go-arrayof-structof,mhennings/marcohennings-go,Triskite/willstone-goclone,glycerine/jeaten-go-arrayof-structof,scirelli/scirelli-go,scirelli/scirelli-go,rflanagan/reginaldflanagan-project1,Triskite/willstone-goclone,glycerine/jeaten-go-arrayof-structof,sanjosh/sanjos100-tipc,Triskite/willstone-goclone,scirelli/scirelli-go,scirelli/scirelli-go,rflanagan/reginaldflanagan-project1,d0f/go-zh,d0f/go-zh,webfd/go-zh,d0f/go-zh,Triskite/willstone-goclone,rdp/rogerpack2005-golang,bryanxu/go-zh,sanjosh/sanjos100-tipc,d0f/go-zh,bryanxu/go-zh,glycerine/jeaten-go-arrayof-structof,rflanagan/reginaldflanagan-project1,rdp/rogerpack2005-golang,Triskite/willstone-goclone,scirelli/scirelli-go,glycerine/jeaten-go-arrayof-structof,d0f/go-zh,webfd/go-zh,glycerine/jeaten-go-arrayof-structof,rdp/rogerpack2005-golang,bryanxu/go-zh,glycerine/jeaten-go-arrayof-structof,webfd/go-zh,mhennings/marcohennings-go,mhennings/marcohennings-go,sanjosh/sanjos100-tipc,rdp/rogerpack2005-golang,mhennings/marcohennings-go,d0f/go-zh,rdp/rogerpack2005-golang,rflanagan/reginaldflanagan-project1,bryanxu/go-zh,sanjosh/sanjos100-tipc,bryanxu/go-zh,webfd/go-zh,scirelli/scirelli-go,webfd/go-zh,rdp/rogerpack2005-golang,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,scirelli/scirelli-go,d0f/go-zh,mhennings/marcohennings-go,webfd/go-zh,bryanxu/go-zh,bryanxu/go-zh,sanjosh/sanjos100-tipc,bryanxu/go-zh,mhennings/marcohennings-go,webfd/go-zh,webfd/go-zh,sanjosh/sanjos100-tipc,Triskite/willstone-goclone,scirelli/scirelli-go,mhennings/marcohennings-go,rdp/rogerpack2005-golang,mhennings/marcohennings-go,Triskite/willstone-goclone,rflanagan/reginaldflanagan-project1