templater: use "needle" and "haystack" as (meta-)variables for ifcontains()
It wasn't immediately clear if it's supposed to look for "search" in "thing" or
"thing" in "search".
#require test-repo
$ . "$TESTDIR/helpers-testrepo.sh"
$ cd "$TESTDIR"/..
New errors are not allowed. Warnings are strongly discouraged.
$ hg files "set:(**.py or **.txt) - tests/**" | sed 's|\\|/|g' |
> python contrib/check-config.py