[[!comment format=mdwn
 username="joey"
 subject="""comment 1"""
 date="2018-10-29T20:04:48Z"
 content="""
To reproduce this bug:

	joey@darkstar:/tmp/t>git annex addurl --fast --raw http://www.google.com/ --file A4.taxfilt.bam
	addurl http://www.google.com/ (to A4.taxfilt.bam) ok
	(recording state in git...)
	joey@darkstar:/tmp/t>git annex get A4.taxfilt.bam
	get A4.taxfilt.bam (from web...) 
	
	ok                             
	(recording state in git...)
	joey@darkstar:/tmp/t>git annex migrate --backend=MD5E A4.taxfilt.bam
	migrate A4.taxfilt.bam failed
	git-annex: migrate: 1 failed

Seems to be a bug in handling backends with fastMigrate = Nothing, causing
it to stop immediately without doing anything. Reversion introduced in
[[!commit 4ecba916a14e02dd62f8ba4257db810fa859f017]].

And calling `stop` in a CommandPerform causes this failure without an
explanation. I think that would be worth cleaning up at some point;
[[todo/do_not_allow_using_stop_in_CommandPerform]].
"""]]