I developed a basic plugin to open a file under git version control in its remote repository using the default browser. Just recently a few users of my plugin have reported the UI freezing (see issue #20). I have been able to reproduce the issue after updating my IDE and creating a new project. The UI completely freezes and the only option is to kill the IntelliJ IDE.
After some digging in the logs I tracked the issue down to the use of the lsRemote command in git4idea here which is used to determine if the current branch exists on the remote before opening it in the browser (falling back to the master branch if it does not). After further investigation I found that the issue is only present when the 'built-in' SSH executable is used which is specified in Preferences → Version Control → Git. Switching the executable to 'Native' works without issue.