don't return uninitialized memory from bdiff.blocks() bdiff.blocks() returns a dummy match at the end of both files; the length of that chunk is never set, so it will sometimes contain random heap garbage. There are apparently workarounds for this elsewhere: # bdiff sometimes gives huge matches past eof, this check eats them,

#!/bin/sh

echo "[extensions]" >> $HGRCPATH
echo "mq=" >> $HGRCPATH

hg init a
cd a
hg qnew first.patch
hg qnew first.patch

touch ../first.patch
hg qimport ../first.patch

exit 0