AFAIK you can use a permissions-only project to achieve that:
- create a permissions-only project [1] named e.g. "Default Settings"
using "gerrit create-project --permissions-only"
- set default settings in this permissions-only project including the merge strategy options
- change parent of all projects which should inherit these settings [2] using
"gerrit set-project-parent --parent <name of the default settings project> <name of the project to reparent>"
- individual projects can still override the settings inherited from their respective parent project
- use "gerrit ls-projects" [3] to create a script doing this for all projects you want to change
the settings for. Alternatively, if you are using Gerrit 2.3, you can use "gerrit set-project-parent"'s
options "--children"-of and "--exclude" to re-parent the projects which should inherit
these default settings
- if you need different types of default settings you may consider to create
different permissions-only projects which may also form an inheritance hierarchy
I think this approach would deserve a new section in the gerrit documentation.
--
Matthias