jrayhawk@richardiv:~/src/cgit$ strace -f bash -c 'CGIT_CONFIG=<(echo scan-path=$PWD; echo email-filter=$PWD/filters/email-libravatar.lua) PATH_INFO=/.git/commit/ ./cgit' 2>&1 | grep 'filters\|liblua'
open("/usr/lib/x86_64-linux-gnu/liblua5.1.so.0", O_RDONLY|O_CLOEXEC) = 3
jrayhawk@richardiv:~/src/cgit$ strace -f bash -c 'CGIT_CONFIG=<(echo scan-path=$PWD; echo email-filter=lua:$PWD/filters/email-libravatar.lua) PATH_INFO=/.git/commit/ ./cgit' 2>&1 | grep 'filters\|liblua'
open("/usr/lib/x86_64-linux-gnu/liblua5.1.so.0", O_RDONLY|O_CLOEXEC) = 3
jrayhawk@richardiv:~/src/cgit$ strace -f bash -c 'CGIT_CONFIG=<(echo scan-path=$PWD; echo email-filter=exec:$PWD/filters/email-libravatar.lua) PATH_INFO=/.git/commit/ ./cgit' 2>&1 | grep 'filters\|liblua'
open("/usr/lib/x86_64-linux-gnu/liblua5.1.so.0", O_RDONLY|O_CLOEXEC) = 3

# At no point does cgit look for the filter.