varnishncsa is missing the -L option to limit the maximum number of incomplete transactions.
Under high traffic environments, varnishncsa will log incomplete log lines due to a VSL overflow
The -L command would exist, similar to varnishlog
Add VSL_OPT_L to varnishncsa_options.h
Add -L limit support to varnishncsa
Add issue 1994 to changelog.
Backport review: applied to 4.1.