fix 'convert' with single commit repositories The attached patch passes the three 'convert' testcases, and also is able to successfully convert the git.git repository.

#!/bin/sh

hg init
python -c 'print "confuse str.splitlines\nembedded\rnewline"' > a
hg ci -Ama -d '1 0'
echo clean diff >> a
hg ci -mb -d '2 0'
hg diff -r0 -r1