### Please describe the problem.

When an assistant adds a lot of new files, and there’s an assistant running for the repo on each of some 5 machines, infinite loop happens on those receiving the new files.

### What steps will reproduce the problem?

1. Have 5 machines with a repo checked out.
2. Run git-annex-assistant on each.
3. Copy a lot of files into the repo on one machine.
4. Look at the webapp UIs on other machines.
5. In the UI, the same files get enqueued and dequeued repeatedly and nothing else happens.

### What version of git-annex are you using? On what operating system?

git-annex version: 6.20170520

local repository version: 6

operating system: linux x86_64

### Please provide any additional information below.

—

### Have you had any luck using git-annex before? (Sometimes we get tired of reading bug reports all day and a lil' positive end note does wonders)

Yes! But do you test it for similar races on more than two simultaneous machines?
