subtree: add build targets 'man' and 'html'

We have targets 'install-man' and 'install-html', let's add build
targets as well.

Signed-off-by: Christian Hesse <mail@eworm.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/subtree/Makefile

@@ -59,6 +59,10 @@ $(GIT_SUBTREE): $(GIT_SUBTREE_SH)
 
 doc: $(GIT_SUBTREE_DOC) $(GIT_SUBTREE_HTML)
 
+man: $(GIT_SUBTREE_DOC)
+
+html: $(GIT_SUBTREE_HTML)
+
 install: $(GIT_SUBTREE)
 	$(INSTALL) -d -m 755 $(DESTDIR)$(gitexecdir)
 	$(INSTALL) -m 755 $(GIT_SUBTREE) $(DESTDIR)$(gitexecdir)