Eu acredito que você queira usar a variável automática $*
. Da documentação do GNU make:
$*
The stem with which an implicit rule matches. If the target is
dir/a.foo.b
and the target pattern isa.%.b
then the stem isdir/foo
. The stem is useful for constructing names of related files. In a static pattern rule, the stem is part of the file name that matched the%
in the target pattern.
No seu caso específico, a regra do wget pode ser reescrita como:
$(BASE_DIR)/$(DATE)/%.csv:
cd $(BASE_DIR)/$(DATE); wget http://example.com/data/$*.csv