But it will use any known version control system (bzr, fossil, git, hg, svn)
to download code from private servers, defined as those hosting packages
matching the GOPRIVATE variable (see 'go help private'). The rationale behind
allowing only Git and Mercurial is that these two systems have had the most
attention to issues of being run as clients of untrusted servers. In contrast,
Bazaar, Fossil, and Subversion have primarily been used in trusted,