As noted in “:help 'packpath'”, the default value is supposed to be the
same as that for 'runtimepath'. This was missed in the original port of
the packages functionality from Vim.
Closes#5193
It is a wrong thing to do, this makes valid variable values be treated
incorrectly: in
XDG_DATA_HOME='/home/$foo/.local/share'
`$foo` should be treated literally and not expanded to `foo` environment
variable value.
Also makes option_expand not try to expand too long strings even if these too
long strings are default values. Previously it thought that default values
should always be expanded. Also does not try to expand NULL should it be the
default value just in case.
Fixes#4961
It is otherwise impossible to determine which test failed sanitizer/valgrind
check. test/functional/helpers.lua module return was changed so that tests which
do not provide after_each function to get new check will automatically fail.
