With the newest release of taskwarrior (2.3.0), it has support for taskd, a task server. (Taskd is currently in the AUR.) However, when trying the syncing features of taskwarrior, I get this error:

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$ task sync init
Taskwarrior was built without GnuTLS support. Sync is not available.
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It's not really documented well, but it looks like during the build process, it looks for the GnuTLS libraries. This is what I get when I run "task diagnostics" from the binary package:

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$ task diagnostics
[...]
Build Features
Built: Jan 24 2014 21:30:18
CMake: 2.8.12.1
Caps: -pthreads -tls
libuuid: libuuid + uuid_unparse_lower
libgnutls: n/a
[...]
----------------------------------

But when I rebuild using the same PKGBUILD and I happen to have gnutls installed:

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$ task diagnostics
[...]
Build Features
Built: Jan 24 2014 16:12:31
CMake: 2.8.12.1
Caps: -pthreads +tls
libuuid: libuuid + uuid_unparse_lower
libgnutls: 3.2.8
[...]
----------------------------------

Now it seems like the syncing with taskd will work.

I guess gnutls can't be an optdepend, since it's a build-time dependency. So maybe it should be added to the depends list?