We actually have a good deal of protection against concurrent runs clobbering each other.
It's not clear to me if you're using "run_branches.pl --run-parallel" or not. If not, you might like to consider changing to that - it's the recommended way of doing concurrent runs. Apart from any other reason it removes the need for a lot of redundant git fetches. By default it staggers concurrent build starts by 60 seconds.
In this case I didn't use run_branches.pl. I just opened up two sessions and triggered two
separate runs for v16 / v17 (with --force) since master just came out green. Efficiency aside,
at worst I was expecting two concurrent runs to be slower, but not error out.
Unrelated, for a slow system my understanding was that it's quite inefficient to keep running older
branches every few minutes (like HEAD does) - so for some of the animals I explicitly run older
branches (for e.g. v13) every few hours, but HEAD runs every few minutes.
Are you saying it's still a good idea to run all together every few minutes (and let older branches
