"Performing VCS Refresh" hang

Hello,

I am using Ultimate 12.1.4 on a project using Maven and Git.  Recently, I am unable to commit changes because IntelliJ hangs with a spinning box "Performing VCS Refresh".

I let it run for a looong time (over an hour) but it didn't finish.

I also tried invalidating caches and restarting.  Didn't help.

What is going on and how can I fix/work around it?

Thanks

Peter