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.
$ hg init
$ echo a > a
$ hg add a
$ hg commit -m test
Do we ever miss a sub-second change?:
$ for i in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20; do
> hg co -qC 0
> echo b > a
> hg st
> done
M a
M a
M a
M a
M a
M a
M a
M a
M a
M a
M a
M a
M a
M a
M a
M a
M a
M a
M a
M a