Fixy.

GNUmakefile

@@ -8,8 +8,8 @@ all: dtpstree
 
 man: man1/dtpstree.1
 
-man1/%.1: % man1/%.1.in
-	help2man -I $@.in -Nn '$(shell sed -e '$$ s|^// ||p;d' $<.cpp)' -o $@ $(shell realpath $<)
+man1/%.1: % %.1.in
+	help2man -I $*.1.in -Nn '$(shell sed -e '$$ s|^// ||p;d' $<.cpp)' -o $@ $(shell realpath $<)
 
 clean:
 	rm -f dtpstree $(wildcard *core)