fix 'got update' of an added + obstructed file
When 'got update' tried to add a new file to the work tree and this
file was obstructed by, say, a directory on disk, the update failed:
$ got update
? new
got: new: Is a directory
$
And the work tree was not updated.
With this commit this situation is properly detected as an obstruction
and the update succeeds:
$ got update
~ new
Updated to refs/heads/master:
c1f85b4938dc4c668a88f13df2b98a520fc077cc
File paths obstructed by a non-regular file: 1
$
Extend a corresponding test case to cover this issue.
ok tracey