. auto-generate per-directory .gitignore files based on $(CLEANFILES)

. gitignore .gitignore files except for the root one.

.gitignore

@@ -24,6 +24,8 @@ GSYMS
 GTAGS
 \#*#
 CVS
+!/.gitignore
+.gitignore
 .svn
 
 boot/boot

share/mk/bsd.prog.mk

@@ -15,6 +15,7 @@
 ##### "all" and "depend" targets
 realinstall: realall
 realall: depend
+depend: .gitignore
 
 ##### Basic targets
 realinstall:	proginstall scriptsinstall
@@ -382,4 +383,7 @@ memalloc: realall
 	${INSTALL} ${INSTALLFLAGS} ${PROG}
 .endif
 
+.gitignore: Makefile
+	echo $(CLEANFILES) $(PROGS) | tr ' ' '\n' >.gitignore
+
 .endif	# HOSTPROG