add first stab at gist TRAMP method
provide access to gh-gist-api by default
fix writable files detection
return more useful results for file-exists-p
more helpers
fix warning
first working version

read-only for now
user is not necessarily current one
allow populating root with other users of interest
handle writable files a bit better
allow advanced revisions
display correct owner (and group) for owned gists
fix insertion for subdirs
handle writing gists
fix permissions for own gists
non-existing files are writable
allow "insertion" of new file
disable auto-save and backup

arguably auto-save should be re-enabled some day
implement file deletion
use magit-git-insert instead of magit-git-output

The latter had been removed from Magit.