"\n" and other characters requiring quoting and/or escaping in
in $GIT_DIR/objects/info/alternates was not supported in git 2.11
and earlier; nor does it seem supported at all in libgit2.
This will allow us to support sharing git-cat-file or similar
endpoints across multiple inboxes via alternates.
This breaks an existing use case for anybody wacky
enough to put `\n' in the `inboxdir' pathname; but I doubt
this affects anybody.