From 10ebac202604f33de2fd35139e4a06ac57164889 Mon Sep 17 00:00:00 2001
From: James Goppert <jgoppert@users.noreply.github.com>
Date: Sat, 8 Apr 2017 23:47:38 -0400
Subject: [PATCH] Fix build when px4 is a submodule (#7006)

* Fix build when px4 is a submodule

* Check if submodule directory exists.

* Fix submodule directory reading
---
 cmake/common/px4_base.cmake | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/cmake/common/px4_base.cmake b/cmake/common/px4_base.cmake
index 647a552203..2088e299c1 100644
--- a/cmake/common/px4_base.cmake
+++ b/cmake/common/px4_base.cmake
@@ -986,10 +986,34 @@ function(px4_create_git_hash_header)
 
 	set(px4_git_ver_header ${PX4_BINARY_DIR}/build_git_version.h)
 
+	# check if px4 source is a git repo
+	if(EXISTS ${PX4_SOURCE_DIR}/.git)
+		if (IS_DIRECTORY ${PX4_SOURCE_DIR}/.git)
+			# standard git repo
+			set(git_dir_path ${PX4_SOURCE_DIR}/.git)
+		else()
+			# git submodule
+			file(READ ${PX4_SOURCE_DIR}/.git git_dir_path)
+			string(STRIP ${git_dir_path} git_dir_path)
+			string(REPLACE "gitdir: " "" git_dir_path ${git_dir_path})
+			get_filename_component(git_dir_path ${git_dir_path} ABSOLUTE)
+		endif()
+	else()
+		message(FATAL_ERROR "is not a git repository")
+	endif()
+	if(NOT IS_DIRECTORY "${git_dir_path}")
+		message(FATAL_ERROR "${git_dir_path} is not a directory")
+	endif()
+
+	set(deps
+		${PX4_SOURCE_DIR}/Tools/px_update_git_header.py
+		${git_dir_path}/index
+		${git_dir_path}/HEAD)
+
 	add_custom_command(
 		OUTPUT ${px4_git_ver_header}
 		COMMAND ${PYTHON_EXECUTABLE} ${PX4_SOURCE_DIR}/Tools/px_update_git_header.py ${px4_git_ver_header} > ${PX4_BINARY_DIR}/git_header.log
-		DEPENDS ${PX4_SOURCE_DIR}/Tools/px_update_git_header.py ${PX4_SOURCE_DIR}/.git/index ${PX4_SOURCE_DIR}/.git/HEAD
+		DEPENDS ${deps}
 		WORKING_DIRECTORY ${PX4_SOURCE_DIR}
 		COMMENT "Generating git hash header"
 		)