Squashed 'posh/posh-tf/' changes from d83696d..9e3b19f

9e3b19f Fix prompt hang in offline or similar cases.
aafdda0 Fix tab completion. Hm, tf.exe forgets to list edit as a command...

git-subtree-dir: posh/posh-tf
git-subtree-split: 9e3b19f0669fc928115e43f1ed9686cdb2658842
Merge commit 'ec9d01b677be4ff6e5907defcfcb07d4434fb460'