auto-upgrade submodules

It only does this if git is clean.

1 files changed, 3 insertions, 1 deletions

diff --git a/Makefile b/Makefile
index 063a4c2..d341da5 100644
--- a/Makefile
+++ b/Makefile
@@ -140,9 +140,11 @@ endif
 
 include user.mk
 
+UPGRADE_SUBMODULES = $(shell a=$$(git status -uno -s) && [ -z "$$a" ] && echo y)
+
 .PHONY: submodule $(SUBMODULES)
 $(SUBMODULES): stack
-        [ -e $@/Makefile ] || git submodule update --init
+        $(if $(UPGRADE_SUBMODULES),, [ -e $@/Makefile ] ||) git submodule update --init
         $(MAKE) -C $@ $(cmd)
 
 install-submodules: cmd=install