deltaparent(): don't return nullrev for a revision containing a full snapshot
this allows us to simplify manifest.readdelta and revlog.revdiff
#!/bin/sh
# test that 'hg commit' does not crash if the user removes a
# newly added file
hg init
echo This is file a1 > a
hg add a
hg commit -m "commit #0" -d "1000000 0"
touch b
hg add b
rm b
hg commit -A -m"comment #1" -d "1000000 0"
exit 0