Fix for quoted variables in command position error message
https://github.com/fish-shell/fish-shell/issues/775
Make funced properly handle an invalid number of arguments
Fixes https://github.com/fish-shell/fish-shell/issues/780
git prompt: Fix hang on detached head.

$git_dir was never set in __fish_git_prompt_current_branch, but used
in the case of a detached HEAD.  This caused `cut -c1-7 $git_dir/HEAD`
to expand to `cut -c1-7` which then waited for input.
Merge remote-tracking branch 'upstream/master'