A few questions about channels

[ison]

Several questions about channels have been on my mind which I haven't been able 
to find any documentation on. So I figured I would ask them all in one place 
since they seem like fairly standard questions that could help others setting 
up channels in the future as well.

1) Is it possible to make a channel from a local git repository? (That is to 
say, a directory on the local machine initialized as a git repository)

2) Is it possible to use private remote repositories as channels? The issue 
here seems to be one of authentication. I'm wonder if there is (or should be) 
an "authentication" field one would add to the channel definition in the 
channels.scm file.

3) How can a channel provide patch files which can be used with 
"search-patches"? I attempted to look through the guix code in gnu/packages.scm 
and from what I can tell it looks like search-patches only looks in paths 
included from "%load-path". There is also a comment saying that it picks up the 
paths from $GUIX_PACKAGE_PATH, but I thought that variable was being deprecated 
in favor of channels. If so, shouldn't search-patches also look inside the 
channels repository for patch files?