hgweb: explictly pass basectx in webutil.diffs
There's only one case where `basectx` parameter is None (over two usages), so
it's probably not worth handling the special case as it makes code-reading
harder.
Along the way, use ctx.p1() instead of checking for ctx.parents() being empty
which should not occur.
#require test-repo
Enable obsolescence to avoid the warning issue when obsmarker are found
$ . "$TESTDIR/helpers-testrepo.sh"
Go back in the hg repo
$ cd $TESTDIR/..
$ for node in `hg log --rev 'not public() and ::. and not desc("# no-check-commit")' --template '{node|short}\n'`; do
> hg export $node | contrib/check-commit > ${TESTTMP}/check-commit.out
> if [ $? -ne 0 ]; then
> echo "Revision $node does not comply with rules"
> echo '------------------------------------------------------'
> cat ${TESTTMP}/check-commit.out
> echo
> fi
> done