In a complex upgrade like qemu 2.8.1.1 -> 2.10.o-rc2, this can take ~ 10 minutes.  Right now, there is no user feedback that progress is being made unless devtool is run with -d. Instead, it looks like devtool upgrade has hung.

We should probably do a progress bar regardless since even if we speed it up a huge (webkit?) upgrade may still be slow. We may also want to look at other ways to do this like using the python git library instead of system calls, or doing some batching of our own, ...
The "culprit" is in scripts/lib/devtool/upgrade.py:
        (stdout,_) = __run('git ls-files --modified --others --exclude-standard')   
        for f in stdout.splitlines():                                                                                                
           __run('git add "%s"' % f)