Failed git commands and StGIT

  Hi,

  a user at #git just came with a problem with stg refresh - it turned
out that he did not have his environment set up properly, but what is
troublesome that stg refresh just said that "git-commit-tree failed" and
did not show the actual error message - looking at the code, you
probably want to keep fd 3 on the parent process' stderr, that is use
open2, not open3.

  The user has used StGIT 0.9.

  Thanks,