User-Agent:       Mozilla/5.0 (X11; Linux x86_64; rv:39.0) Gecko/20100101
Firefox/39.0
Build Identifier: 

One-Click-Installer YMP files can contain sections for different distribution
versions, e.g.:
<group distversion="openSUSE 13.2">

You can match against a specific Tumbleweed build:
<group distversion="openSUSE 20150924">

But it's not possible to match for Tumbleweed in general because the version of
Tumbleweed changes with every build.

Can the one-click-installer be extended to not only match against the version
but also against the codename?

For example:
<group distcodename="openSUSE Tumbleweed">


Reproducible: Always