parsers: fix uninitialize variable warning The heads pointer is not initialized correctly if filter is false, causing both clang and gcc to issue a warning. Correctly initialize heads to NULL.

CC := gcc
CFLAGS := -g -O2 -Wall -Werror

prefix ?= /usr/bin

hgsh: hgsh.o
	$(CC) -o $@ $<

install: hgsh
	install -m755 hgsh $(prefix)

clean:
	rm -f *.o hgsh