Add MMM-physics as a git submodule

.gitmodules

@@ -4,6 +4,9 @@
 [submodule ".ci/hpc-workflows"]
 	path = .ci/hpc-workflows
 	url = https://github.com/islas/hpc-workflows
+[submodule "phys/physics_mmm"]
+	path = phys/physics_mmm
+	url = https://github.com/NCAR/MMM-physics.git
 [submodule "phys/MYNN-EDMF"]
 	path = phys/MYNN-EDMF
 	url = https://github.com/NCAR/MYNN-EDMF

arch/Externals.cfg

@@ -1,10 +1,2 @@
-[MMM-physics]
-local_path = ./phys/physics_mmm
-protocol = git
-repo_url = https://github.com/NCAR/MMM-physics.git
-tag = 20240626-MPASv8.2
-
-required = True
-
 [externals_description]
 schema_version = 1.0.0

phys/Makefile

@@ -277,6 +277,12 @@ submodules :
 	else \
 		echo No action required for NoahMP submodule ; \
 	fi
+	@if [ \( ! -f phys/physics_mmm/README.md \) ] ; then \
+		echo Pulling in MMM-physics submodule ; \
+		( cd .. ; git submodule update --init --recursive ) ; \
+	else \
+		echo No action required for MMM-physics submodule ; \
+	fi
 	@if [ \( ! -f module_bl_mynnedmf.F \) -o \( ! -f module_bl_mynnedmf_common.F \) -o \
 	      \( ! -f module_bl_mynnedmf_driver.F \) ] ; then \
 	      	echo Pulling in MYNN-EDMF submodule ; \