test-gpg: start gpg-agent by gpg-connect-agent only if GnuPG v2.1+ detected
Danek Duvall found that gpg-connect-agent of GnuPG 2.0 never starts gpg-agent
daemon. The 2.1 way is documented as "gpg-coonect-agent /bye" [1], which
appears to be different from the 2.0 way [2].
[1]: https://www.gnupg.org/documentation/manuals/gnupg/Invoking-GPG_002dAGENT.html
[2]: https://www.gnupg.org/documentation/manuals/gnupg-2.0/Invoking-GPG_002dAGENT.html
Since "gpg-agent --daemon" of GnuPG 2.1 never prints environment variables,
"eval $(gpg-agent --daemon)" would be valid only for GnuPG < 2.1, and we'll
need a different workaround for 2.0. I have no 2.0 environment, I won't
implement it.
Issue351: mq: qrefresh can create extra revlog entry
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init
$ hg qinit
$ echo b > b
$ hg ci -A -m foo
adding b
$ echo cc > b
$ hg qnew -f foo.diff
$ echo b > b
$ hg qrefresh
$ hg debugindex b
rev offset length ..... linkrev nodeid p1 p2 (re)
0 0 3 ..... 0 1e88685f5dde 000000000000 000000000000 (re)