add paragraph to cdist-hacker that states manpages always need to build on merge request

Signed-off-by: Nico Schottelius <nico@kr.ethz.ch>

doc/man/man7/cdist-hacker.text

@@ -46,9 +46,8 @@ work nor kill the authors brain:
   private branch!
 - Code to be included should be branched of the upstream "master" branch
    - Exception: Bugfixes to a version branch
-- Code submissions should be in your master branch
-   - Other branches are fine as well, but you need to tell me which branch
-     your work is in!
+- On a merge request, always name the branch I should pull from
+- Always ensure **all** manpages build: ./build.sh man
 - If you developed more than **one** feature, consider submitting them in
   seperate branches. This way one feature can already be included, even if
   the other needs to be improved.