Fix and improve parts of rbt patch.
There were a few things with rbt patch that made usage difficult.
It wouldn't allow for creating a commit if there was even one untracked

file in the checkout, even though those shouldn't have been a factor.

They were a factor, though, because of the next issue, which was that

every single file (tracked and untracked) would be committed along with

the patch. It would do this in order to include any files modified or

introduced in the patch.
The cleanliness restriction has been reduced. Tracked files with

modifications in the working directory or index will now prevent rbt

patch from creating a commit, but untracked files will not. When calling

git apply, we now pass --index, which will apply the changes to the

index, including the addition of any files. This means we only need to

do a plain git commit at the end.
And last but not least, the change from a rich_text field in the API

to text_type broke unescaping, but unescaping can now be done

server-side. We now pass ?force-text-type=plain to get the

unescaped version. (This parameter is simply ignored for older

releases.)

Applied a change with modified and new files to a tree with untracked files.

It applied and was committed without yelling at me or impacting my

untracked files.