debugcommands: introduce debugpeer command
`hg debugpeer <path>` will establish a connection to a peer repository
and print information about it.
If you add --debug, it will log low-level protocol request info. This
will be useful for upcoming tests around protocol handshaking.
Differential Revision: https://phab.mercurial-scm.org/D2025
#require docutils gettext
$ $TESTDIR/check-gendoc de
checking for parse errors
Die Dateien werden dem Projektarchiv beim n\xc3\xa4chsten \xc3\x9cbernehmen (commit) hinzugef\xc3\xbcgt. Um dies vorher r\xc3\xbcckg\xc3\xa4ngig zu machen, siehe:hg:`forget`. (esc)
warning: please have a space before :hg: