tests/narrow-library.sh

lfs: add a blob verification method to the local store

A corrupt blob can be signaled through the Batch API response, without actually
transferring the file.  A true/false indicator is slightly easier than
immediately catching an exception.

cat >> $HGRCPATH <<EOF
[extensions]
narrow=
[ui]
ssh=python "$TESTDIR/dummyssh"
[experimental]
changegroup3 = True
EOF