From 11deae4782811c1d8a2860f5d3dca57c3c06ccfb Mon Sep 17 00:00:00 2001
From: midipix <writeonce@midipix.org>
Date: Wed, 21 Sep 2016 22:37:06 -0400
Subject: build system: support setting an external folder as the source
 directory.

---
 Makefile.in  |  7 ++++---
 config.usage |  2 ++
 configure    | 42 +++++++++++++++++++++++++++++++++++-------
 3 files changed, 41 insertions(+), 10 deletions(-)

diff --git a/Makefile.in b/Makefile.in
index 8d3e543..1bbc47f 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -1,6 +1,7 @@
 PACKAGE 		= @package@
 NICKNAME 		= @nickname@
 PROJECT_DIR 		= @project_dir@
+SOURCE_DIR 		= @source_dir@
 GIT_REFERENCE_INDEX	= @git_reference_index@
 CUSTOM_INSTALL_HEADERS  = @custom_install_headers@
 AVOID_VERSION		= @avoid_version@
@@ -101,10 +102,10 @@ include $(PROJECT_DIR)/project/overrides.mk
 
 $(APP_SRCS:%.c=%.o): CFLAGS_STATIC = $(CFLAGS_APP)
 
-src/%.lo: 	$(PROJECT_DIR)/src/%.c $(ALL_HEADERS) host.tag tree.tag
+src/%.lo: 	$(SOURCE_DIR)/src/%.c $(ALL_HEADERS) host.tag tree.tag
 		$(CC) -c -o $@ $< $(CFLAGS_SHARED)
 
-src/%.o: 	$(PROJECT_DIR)/src/%.c $(ALL_HEADERS) host.tag tree.tag
+src/%.o: 	$(SOURCE_DIR)/src/%.c $(ALL_HEADERS) host.tag tree.tag
 		$(CC) -c -o $@ $< $(CFLAGS_STATIC)
 
 lib/%$(OS_LIB_SUFFIX)$(VER_XYZ):
@@ -220,7 +221,7 @@ host.tag:	Makefile
 
 version.tag:	$(GIT_REFERENCE_INDEX)
 		$(PROJECT_DIR)/sysinfo/version.sh	\
-			-s $(PROJECT_DIR)		\
+			-s $(SOURCE_DIR)		\
 			-o build/$(PACKAGE)_version.h	\
 			-p $(PACKAGE)
 		touch version.tag
diff --git a/config.usage b/config.usage
index 47599e9..4a351e4 100644
--- a/config.usage
+++ b/config.usage
@@ -6,6 +6,7 @@ supported switches:
 
 	--nickname
 	--avoid-version
+	--source-dir
 
 	--prefix
 	--exec-prefix
@@ -47,6 +48,7 @@ supported switches:
 supported variables:
 --------------------
 	NICKNAME
+	SOURCE_DIR
 
 	PREFIX
 	EXEC_PREFIX
diff --git a/configure b/configure
index 6894bc6..6875689 100755
--- a/configure
+++ b/configure
@@ -33,13 +33,9 @@ init_vars()
 		. "$mb_config" || exit 2
 	fi
 
-	# git
-	if [ -d "$mb_project_dir/.git" ]; then
-		mb_git_reference_index="\$(PROJECT_DIR)/.git/index"
-	fi
-
 	# project
 	mb_nickname=$NICKNAME
+	mb_source_dir=$SOURCE_DIR
 
 	# dirs
 	mb_prefix=$PREFIX
@@ -124,10 +120,33 @@ verify_build_directory()
 }
 
 
+verify_source_directory()
+{
+	if [ -z "$mb_source_dir" ]; then
+		if [ "$mb_require_source_dir" = yes ]; then
+			error_msg "$mb_package: specifying an external source directory is required."
+			error_msg "you can set the source directory either via --source-dir=<path>,"
+			error_msg "or by setting the SOURCE_DIR variable."
+			exit 2
+		fi
+	fi
+}
+
+
 common_defaults()
 {
+	# git
+	if [ -n "$mb_source_dir" ]; then
+		if [ -d "$mb_source_dir/.git" ]; then
+			mb_git_reference_dir="\$(SOURCE_DIR)/.git"
+		fi
+	elif [ -d "$mb_project_dir/.git" ]; then
+		mb_git_reference_dir="\$(PROJECT_DIR)/.git"
+	fi
+
 	# project
 	[ -z "$mb_nickname" ] 		&& mb_nickname=$mb_package
+	[ -z "$mb_source_dir" ] 	&& mb_source_dir=$mb_project_dir
 	[ -z "$mb_avoid_version" ] 	&& mb_avoid_version='no'
 
 	# dirs
@@ -370,6 +389,7 @@ config_copy()
 	sed 		-e 's^@package@^'"$mb_package"'^g' 				\
 			-e 's^@nickname@^'"$mb_nickname"'^g'				\
 			-e 's^@project_dir@^'"$mb_project_dir"'^g'			\
+			-e 's^@source_dir@^'"$mb_source_dir"'^g'			\
 			-e 's^@git_reference_index@^'"$mb_git_reference_index"'^g'	\
 			-e 's^@custom_install_headers@^'"$mb_custom_install_headers"'^g' \
 			-e 's^@avoid_version@^'"$mb_avoid_version"'^g'			\
@@ -604,6 +624,9 @@ for arg ; do
 		--avoid-version)
 			mb_avoid_version='yes'
 			;;
+		--source-dir=*)
+			mb_source_dir=${arg#*=}
+			;;
 
 		*)
 			error_msg ${arg#}: "unsupported config argument."
@@ -614,14 +637,19 @@ done
 
 
 
-# three: defaults
+# three: validation
+verify_source_directory
+
+
+
+# four: defaults
 common_defaults
 native_defaults
 cross_defaults
 
 
 
-# four: config
+# five: config
 config_flags
 config_copy
 config_support
-- 
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