help: always suggest common-cmds if prefix of cmd

If someone runs "git st", the command "git status" is not suggested
because it's not one of the closest levenshtein-neighbour.

Reserve the distance of 0 for common commands where the entered command
is a prefixe, as these are often more likely to be what the user meant.

This way, "git status" is the first suggestion, while a list of possible
typos are still suggested as well.

Signed-off-by: Erik Faye-Lund <kusmabite@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/Makefile b/Makefile
index 919ed2b..7baa621 100644
--- a/Makefile
+++ b/Makefile
@@ -1620,6 +1620,8 @@
 	$(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ git.o \
 		$(BUILTIN_OBJS) $(ALL_LDFLAGS) $(LIBS)
 
+help.o: common-cmds.h
+
 builtin/help.o: common-cmds.h
 builtin/help.s builtin/help.o: EXTRA_CPPFLAGS = \
 	'-DGIT_HTML_PATH="$(htmldir_SQ)"' \