Use CMake to fetch submodules

Custom CMake module which attempts to automatically clone submodules when they're missing.  Uses the `--depth` option if supported, which should be faster than running `--recursive` on initial clone.

CMakeLists.txt

@@ -13,6 +13,7 @@ IF(COMMAND CMAKE_POLICY)
 	ENDIF()
 ENDIF(COMMAND CMAKE_POLICY)
 
+INCLUDE(CheckSubmodules)
 INCLUDE(AddFileDependencies)
 INCLUDE(CheckIncludeFiles)
 INCLUDE(FindPkgConfig)

cmake/modules/CheckSubmodules.cmake

@@ -0,0 +1,138 @@
+# Utility for validating and, if needed, cloning all submodules
+#
+# Looks for a .gitmodules in the root project folder
+# Loops over all modules looking well-known configure/build scripts
+#
+# Usage:
+#       INCLUDE(CheckSubmodules)
+#
+# Options:
+#       SET(SKIP_SUBMODULES "foo;bar")
+#
+# Or via command line:       
+#       cmake -DSKIP_SUBMODULES=foo;bar
+#
+# Copyright (c) 2017, Tres Finocchiaro, <tres.finocchiaro@gmail.com>
+#
+# Redistribution and use is allowed according to the terms of the BSD license.
+# For details see the accompanying COPYING-CMAKE-SCRIPTS file.
+
+# Files which confirm a successful clone
+SET(VALID_CRUMBS "CMakeLists.txt;Makefile;Makefile.in;Makefile.am;configure.ac;configure.py;autogen.sh")
+
+# Try and use the specified shallow clone on submodules, if supported
+SET(DEPTH_VALUE 100)
+
+# Number of times git commands will retry before failing
+SET(MAX_ATTEMPTS 2)
+
+MESSAGE("\nValidating submodules...")
+FILE(READ "${CMAKE_SOURCE_DIR}/.gitmodules" SUBMODULE_DATA)
+
+# Assume alpha-numeric paths
+STRING(REGEX MATCHALL "path = [-0-9A-Za-z/]+" SUBMODULE_LIST ${SUBMODULE_DATA})
+FOREACH(_part ${SUBMODULE_LIST})
+	STRING(REPLACE "path = " "" SUBMODULE_PATH ${_part})
+
+	# Remove submodules from validation as specified in -DSKIP_SUBMODULES=foo;bar
+	SET(SKIP false)
+	IF(SKIP_SUBMODULES)
+		FOREACH(_skip ${SKIP_SUBMODULES})
+			IF(${SUBMODULE_PATH} MATCHES ${_skip})
+				MESSAGE("-- Skipping ${SUBMODULE_PATH} matches \"${_skip}\"")
+				SET(SKIP true)
+			ENDIF()
+		ENDFOREACH()
+	ENDIF()
+	LIST(REMOVE_ITEM SUBMODULE_LIST ${_part})
+	IF(NOT SKIP)
+		LIST(APPEND SUBMODULE_LIST ${SUBMODULE_PATH})
+	ENDIF()
+ENDFOREACH()
+
+LIST(SORT SUBMODULE_LIST)
+
+# Once called, status is stored in GIT_RESULT respectively.
+# Note: Git likes to write to stderr.  Don't assume stderr is error; Check GIT_RESULT instead.
+MACRO(GIT_SUBMODULE SUBMODULE_PATH FORCE_DEINIT)
+	FIND_PACKAGE(Git REQUIRED)
+	IF(${FORCE_DEINIT})
+		MESSAGE("--   Resetting ${SUBMODULE_PATH}")
+		EXECUTE_PROCESS(
+			COMMAND ${GIT_EXECUTABLE} submodule deinit -f ${CMAKE_SOURCE_DIR}/${SUBMODULE_PATH}
+			WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
+			OUTPUT_QUIET
+		)
+		# Recurse
+		GIT_SUBMODULE(${SUBMODULE_PATH} false)
+	ELSE()
+		# Try to use the depth switch
+		SET(DEPTH_CMD "")
+			MESSAGE("--   Fetching ${SUBMODULE_PATH}")
+		IF(DEPTH_VALUE)
+			SET(DEPTH_CMD "--depth" )
+			MESSAGE("--   Fetching ${SUBMODULE_PATH} @ --depth ${DEPTH_VALUE}")
+		ENDIF()
+		
+		EXECUTE_PROCESS(
+			COMMAND ${GIT_EXECUTABLE} submodule update --init --recursive ${DEPTH_CMD} ${DEPTH_VALUE} ${CMAKE_SOURCE_DIR}/${SUBMODULE_PATH}
+			WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
+			RESULT_VARIABLE GIT_RESULT
+			OUTPUT_VARIABLE GIT_STDOUT
+			ERROR_VARIABLE GIT_STDERR
+		)
+
+		SET(GIT_MESSAGE "${GIT_STDOUT}${GIT_STDERR}")
+		MESSAGE(${GIT_MESSAGE})
+	ENDIF()
+ENDMACRO()
+
+SET(RETRY_PHRASES "Failed to recurse;unadvertised object;cannot create directory")
+
+# Attempt to do lazy clone
+FOREACH(_submodule ${SUBMODULE_LIST})
+	STRING(REPLACE "/" ";" PATH_PARTS ${_submodule})
+	LIST(REVERSE PATH_PARTS)
+	LIST(GET PATH_PARTS 0 SUBMODULE_NAME)
+
+	MESSAGE("-- Checking ${SUBMODULE_NAME}...")
+	SET(CRUMB_FOUND false)
+	FOREACH(_crumb ${VALID_CRUMBS})
+		IF(EXISTS "${CMAKE_SOURCE_DIR}/${_submodule}/${_crumb}")
+			SET(CRUMB_FOUND true)
+			MESSAGE("--   Found ${_submodule}/${_crumb}")
+		ENDIF()
+	ENDFOREACH()
+	IF(NOT CRUMB_FOUND)
+		GIT_SUBMODULE(${_submodule} false)
+
+		SET(COUNTED 0)
+		SET(COUNTING "")
+		# Handle edge-cases where submodule didn't clone properly or re-uses a non-empty directory
+		WHILE(NOT GIT_RESULT EQUAL 0 AND COUNTED LESS MAX_ATTEMPTS)
+			LIST(APPEND COUNTING "x")
+			LIST(LENGTH COUNTING COUNTED)
+
+			FOREACH(_phrase ${RETRY_PHRASES})
+				IF("${GIT_MESSAGE}" MATCHES "${_phrase}")
+					MESSAGE("--   Retrying ${_submodule} using 'deinit' (attempt ${COUNTED} of ${MAX_ATTEMPTS})...")
+					
+					# Shallow submodules were introduced in 1.8.4
+					# Shallow commits can fail to clone from non-default branches, only try once
+					IF(GIT_VERSION_STRING VERSION_GREATER "1.8.3" AND COUNTED LESS 2)
+						# Try a shallow submodule clone
+					ELSE()
+						UNSET(DEPTH_VALUE)
+					ENDIF()
+					
+					GIT_SUBMODULE(${_submodule} true)
+				ENDIF()
+			ENDFOREACH()
+		ENDWHILE()
+
+		IF(NOT GIT_RESULT EQUAL 0)
+			MESSAGE(FATAL_ERROR "${GIT_EXECUTABLE} exited with status of ${GIT_RESULT}")
+		ENDIF()
+	ENDIF()
+ENDFOREACH()
+MESSAGE("-- Done validating submodules.\n")

src/CMakeLists.txt

@@ -160,10 +160,12 @@ TARGET_LINK_LIBRARIES(lmms
 )
 
 FOREACH(LIB ${LMMS_REQUIRED_LIBS})
-    GET_TARGET_PROPERTY(INCLUDE_DIRS ${LIB} INTERFACE_INCLUDE_DIRECTORIES)
-    if (INCLUDE_DIRS)
-        TARGET_INCLUDE_DIRECTORIES(lmmsobjs PRIVATE ${INCLUDE_DIRS})
-    ENDIF()
+	IF(TARGET ${LIB})
+		GET_TARGET_PROPERTY(INCLUDE_DIRS ${LIB} INTERFACE_INCLUDE_DIRECTORIES)
+		IF(INCLUDE_DIRS)
+			TARGET_INCLUDE_DIRECTORIES(lmmsobjs PRIVATE ${INCLUDE_DIRS})
+		ENDIF()
+	ENDIF()
 ENDFOREACH()