CommandOutputHandler.getOutput() is called before CommandOutputHandler.process() returns

Issue Summary

This issue started happening in Bitbucket 8. Everything works fine in previous releases.

Due to this regression getOutput() can be called before process() completes in cases where the underlying command has already returned.

For example:

After calling git cat-file, once all the output from git has been read into CommandOutputHandler's internal buffer, git exits. However, there is additional processing before the output is ready. In this case, there’s a race between finishing the processing of data and getOutput() being called.

Steps to Reproduce

1. Call git cat-file
2. Once all the output from git has been read into CommandOutputHandler's internal buffer, git exits.

Expected Results

All the processing has been done/completed and we can safely call  getOutput() 

Actual Results

There is still additional processing to be done before the output is ready and therefore we get into a race condition between finishing the processing of data and getOutput() being called.

Workaround

No workaround available at the moment.