cmake: use PROJECT_SOURCE_DIR of CMAKE_SOURCE_DIR

Also applies to *_BINARY_DIR.

This effectively reverts 84083dc,
which broke all users of libgit2 that use it as a CMake subdirectory
(via `add_subdirectory()`). This is because CMAKE_SOURCE_DIR refers
to the root-most CMake directory, which in the case of
`add_subdirectory()` is a parent project to libgit2 and thus the paths
don't make any sense to the configuration files. Corollary,
CMAKE_SOURCE_DIR only makes sense if the CMake project is always the
root project - which can rarely be guaranteed.

In all honesty, CMake should deprecate and eventually remove
CMAKE_SOURCE_DIR and CMAKE_BINARY_DIR. It's been the source of headaches
and confusion for years, they're rarely useful over
CMAKE_CURRENT_(SOURCE|BINARY)_DIR or PROJECT_(SOURCE|BINARY)_DIR,
and they cause a lot of confusing configuration and source
code layouts to boot.

Any time they are used, they break `add_subdirectory()` almost 100% of
the time, cause confusing error messages, and hide subtle bugs.

Author: Qix-

CMakeLists.txt

@@ -6,7 +6,7 @@ cmake_minimum_required(VERSION 3.5.1)
 project(libgit2 VERSION "1.3.0" LANGUAGES C)
 
 # Add find modules to the path
-set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}/cmake")
+set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${PROJECT_SOURCE_DIR}/cmake")
 
 #
 # Build options

cmake/IdeSplitSources.cmake

@@ -8,7 +8,7 @@ function(IDE_SPLIT_SOURCES target)
 		get_target_property(sources ${target} SOURCES)
 		foreach(source ${sources})
 			if(source MATCHES ".*/")
-				string(REPLACE ${CMAKE_SOURCE_DIR}/ "" rel ${source})
+				string(REPLACE ${PROJECT_SOURCE_DIR}/ "" rel ${source})
 				if(rel)
 					string(REGEX REPLACE "/([^/]*)$" "" rel ${rel})
 					if(rel)

cmake/SelectHTTPParser.cmake

@@ -12,8 +12,8 @@ if(USE_HTTP_PARSER STREQUAL "system")
 	endif()
 else()
 	message(STATUS "http-parser version 2 was not found or disabled; using bundled 3rd-party sources.")
-	add_subdirectory("${CMAKE_SOURCE_DIR}/deps/http-parser" "${CMAKE_BINARY_DIR}/deps/http-parser")
-	list(APPEND LIBGIT2_DEPENDENCY_INCLUDES "${CMAKE_SOURCE_DIR}/deps/http-parser")
+	add_subdirectory("${PROJECT_SOURCE_DIR}/deps/http-parser" "${PROJECT_BINARY_DIR}/deps/http-parser")
+	list(APPEND LIBGIT2_DEPENDENCY_INCLUDES "${PROJECT_SOURCE_DIR}/deps/http-parser")
 	list(APPEND LIBGIT2_DEPENDENCY_OBJECTS "$<TARGET_OBJECTS:http-parser>")
 	add_feature_info(http-parser ON "http-parser support (bundled)")
 endif()

cmake/SelectRegex.cmake

@@ -43,8 +43,8 @@ elseif(REGEX_BACKEND STREQUAL "builtin")
 	add_feature_info(regex ON "using bundled PCRE")
 	set(GIT_REGEX_BUILTIN 1)
 
-	add_subdirectory("${CMAKE_SOURCE_DIR}/deps/pcre" "${CMAKE_BINARY_DIR}/deps/pcre")
-	list(APPEND LIBGIT2_DEPENDENCY_INCLUDES "${CMAKE_SOURCE_DIR}/deps/pcre")
+	add_subdirectory("${PROJECT_SOURCE_DIR}/deps/pcre" "${PROJECT_BINARY_DIR}/deps/pcre")
+	list(APPEND LIBGIT2_DEPENDENCY_INCLUDES "${PROJECT_SOURCE_DIR}/deps/pcre")
 	list(APPEND LIBGIT2_DEPENDENCY_OBJECTS $<TARGET_OBJECTS:pcre>)
 else()
 	message(FATAL_ERROR "The REGEX_BACKEND option provided is not supported")

cmake/SelectWinHTTP.cmake

@@ -4,9 +4,9 @@ if(WIN32 AND USE_WINHTTP)
 	# Since MinGW does not come with headers or an import library for winhttp,
 	# we have to include a private header and generate our own import library
 	if(MINGW)
-		add_subdirectory("${CMAKE_SOURCE_DIR}/deps/winhttp" "${CMAKE_BINARY_DIR}/deps/winhttp")
+		add_subdirectory("${PROJECT_SOURCE_DIR}/deps/winhttp" "${PROJECT_BINARY_DIR}/deps/winhttp")
 		list(APPEND LIBGIT2_SYSTEM_LIBS winhttp)
-		list(APPEND LIBGIT2_DEPENDENCY_INCLUDES "${CMAKE_SOURCE_DIR}/deps/winhttp")
+		list(APPEND LIBGIT2_DEPENDENCY_INCLUDES "${PROJECT_SOURCE_DIR}/deps/winhttp")
 	else()
 		list(APPEND LIBGIT2_SYSTEM_LIBS "winhttp")
 		list(APPEND LIBGIT2_PC_LIBS "-lwinhttp")

cmake/SelectZlib.cmake

@@ -22,13 +22,13 @@ if(USE_BUNDLED_ZLIB STREQUAL "OFF")
 	endif()
 endif()
 if(USE_BUNDLED_ZLIB STREQUAL "Chromium")
-	add_subdirectory("${CMAKE_SOURCE_DIR}/deps/chromium-zlib" "${CMAKE_BINARY_DIR}/deps/chromium-zlib")
-	list(APPEND LIBGIT2_DEPENDENCY_INCLUDES "${CMAKE_SOURCE_DIR}/deps/chromium-zlib")
+	add_subdirectory("${PROJECT_SOURCE_DIR}/deps/chromium-zlib" "${PROJECT_BINARY_DIR}/deps/chromium-zlib")
+	list(APPEND LIBGIT2_DEPENDENCY_INCLUDES "${PROJECT_SOURCE_DIR}/deps/chromium-zlib")
 	list(APPEND LIBGIT2_DEPENDENCY_OBJECTS $<TARGET_OBJECTS:chromium_zlib>)
 	add_feature_info(zlib ON "using (Chromium) bundled zlib")
 elseif(USE_BUNDLED_ZLIB OR NOT ZLIB_FOUND)
-	add_subdirectory("${CMAKE_SOURCE_DIR}/deps/zlib" "${CMAKE_BINARY_DIR}/deps/zlib")
-	list(APPEND LIBGIT2_DEPENDENCY_INCLUDES "${CMAKE_SOURCE_DIR}/deps/zlib")
+	add_subdirectory("${PROJECT_SOURCE_DIR}/deps/zlib" "${PROJECT_BINARY_DIR}/deps/zlib")
+	list(APPEND LIBGIT2_DEPENDENCY_INCLUDES "${PROJECT_SOURCE_DIR}/deps/zlib")
 	list(APPEND LIBGIT2_DEPENDENCY_OBJECTS $<TARGET_OBJECTS:zlib>)
 	add_feature_info(zlib ON "using bundled zlib")
 endif()

deps/winhttp/CMakeLists.txt

@@ -3,7 +3,7 @@ if(NOT DLLTOOL)
 	message(FATAL_ERROR "Could not find dlltool command")
 endif()
 
-set(LIBWINHTTP_PATH "${CMAKE_BINARY_DIR}/deps/winhttp")
+set(LIBWINHTTP_PATH "${PROJECT_BINARY_DIR}/deps/winhttp")
 set(LIBWINHTTP_PATH ${LIBWINHTTP_PATH} PARENT_SCOPE)
 file(MAKE_DIRECTORY ${LIBWINHTTP_PATH})
 

src/CMakeLists.txt

@@ -36,8 +36,8 @@ set(LIBGIT2_PC_LIBS "")
 
 set(LIBGIT2_INCLUDES
 	"${CMAKE_CURRENT_BINARY_DIR}"
-	"${CMAKE_SOURCE_DIR}/src"
-	"${CMAKE_SOURCE_DIR}/include")
+	"${PROJECT_SOURCE_DIR}/src"
+	"${PROJECT_SOURCE_DIR}/include")
 
 if(HAVE_FUTIMENS)
 	set(GIT_USE_FUTIMENS 1)
@@ -117,8 +117,8 @@ target_sources(git2internal PRIVATE ${SRC_SHA1})
 # Optional external dependency: ntlmclient
 if(USE_NTLMCLIENT)
 	set(GIT_NTLM 1)
-	add_subdirectory("${CMAKE_SOURCE_DIR}/deps/ntlmclient" "${CMAKE_BINARY_DIR}/deps/ntlmclient")
-	list(APPEND LIBGIT2_DEPENDENCY_INCLUDES "${CMAKE_SOURCE_DIR}/deps/ntlmclient")
+	add_subdirectory("${PROJECT_SOURCE_DIR}/deps/ntlmclient" "${PROJECT_BINARY_DIR}/deps/ntlmclient")
+	list(APPEND LIBGIT2_DEPENDENCY_INCLUDES "${PROJECT_SOURCE_DIR}/deps/ntlmclient")
 	list(APPEND LIBGIT2_DEPENDENCY_OBJECTS "$<TARGET_OBJECTS:ntlmclient>")
 endif()
 add_feature_info(ntlmclient GIT_NTLM "NTLM authentication support for Unix")
@@ -164,9 +164,9 @@ target_compile_definitions(git2internal PRIVATE _FILE_OFFSET_BITS=64)
 
 # Collect sourcefiles
 file(GLOB SRC_H
-	"${CMAKE_SOURCE_DIR}/include/git2.h"
-	"${CMAKE_SOURCE_DIR}/include/git2/*.h"
-	"${CMAKE_SOURCE_DIR}/include/git2/sys/*.h")
+	"${PROJECT_SOURCE_DIR}/include/git2.h"
+	"${PROJECT_SOURCE_DIR}/include/git2/*.h"
+	"${PROJECT_SOURCE_DIR}/include/git2/sys/*.h")
 list(SORT SRC_H)
 target_sources(git2internal PRIVATE ${SRC_H})
 
@@ -225,7 +225,7 @@ configure_file(features.h.in git2/sys/features.h)
 ide_split_sources(git2internal)
 list(APPEND LIBGIT2_OBJECTS $<TARGET_OBJECTS:git2internal> ${LIBGIT2_DEPENDENCY_OBJECTS})
 
-target_include_directories(git2internal PRIVATE ${LIBGIT2_INCLUDES} ${LIBGIT2_DEPENDENCY_INCLUDES} PUBLIC ${CMAKE_SOURCE_DIR}/include)
+target_include_directories(git2internal PRIVATE ${LIBGIT2_INCLUDES} ${LIBGIT2_DEPENDENCY_INCLUDES} PUBLIC ${PROJECT_SOURCE_DIR}/include)
 target_include_directories(git2internal SYSTEM PRIVATE ${LIBGIT2_SYSTEM_INCLUDES})
 
 set(LIBGIT2_INCLUDES ${LIBGIT2_INCLUDES} PARENT_SCOPE)
@@ -247,9 +247,9 @@ add_library(git2 ${WIN_RC} ${LIBGIT2_OBJECTS})
 target_link_libraries(git2 ${LIBGIT2_SYSTEM_LIBS})
 
 set_target_properties(git2 PROPERTIES C_STANDARD 90)
-set_target_properties(git2 PROPERTIES LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR})
-set_target_properties(git2 PROPERTIES RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR})
-set_target_properties(git2 PROPERTIES ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR})
+set_target_properties(git2 PROPERTIES LIBRARY_OUTPUT_DIRECTORY ${PROJECT_BINARY_DIR})
+set_target_properties(git2 PROPERTIES RUNTIME_OUTPUT_DIRECTORY ${PROJECT_BINARY_DIR})
+set_target_properties(git2 PROPERTIES ARCHIVE_OUTPUT_DIRECTORY ${PROJECT_BINARY_DIR})
 
 # Workaround for Cmake bug #0011240 (see http://public.kitware.com/Bug/view.php?id=11240)
 # Win64+MSVC+static libs = linker error
@@ -290,5 +290,5 @@ install(TARGETS git2
 	LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
 	ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
 )
-install(DIRECTORY ${CMAKE_SOURCE_DIR}/include/git2 DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
-install(FILES ${CMAKE_SOURCE_DIR}/include/git2.h DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
+install(DIRECTORY ${PROJECT_SOURCE_DIR}/include/git2 DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
+install(FILES ${PROJECT_SOURCE_DIR}/include/git2.h DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})

tests/CMakeLists.txt

@@ -38,7 +38,7 @@ set_source_files_properties(
 add_executable(libgit2_tests ${SRC_CLAR} ${SRC_TEST} ${LIBGIT2_OBJECTS})
 
 set_target_properties(libgit2_tests PROPERTIES C_STANDARD 90)
-set_target_properties(libgit2_tests PROPERTIES RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR})
+set_target_properties(libgit2_tests PROPERTIES RUNTIME_OUTPUT_DIRECTORY ${PROJECT_BINARY_DIR})
 
 target_include_directories(libgit2_tests PRIVATE ${TEST_INCLUDES} ${LIBGIT2_INCLUDES} ${LIBGIT2_DEPENDENCY_INCLUDES})
 target_include_directories(libgit2_tests SYSTEM PRIVATE ${LIBGIT2_SYSTEM_INCLUDES})
@@ -62,9 +62,9 @@ endif()
 
 function(ADD_CLAR_TEST name)
 	if(NOT USE_LEAK_CHECKER STREQUAL "OFF")
-		add_test(${name} "${CMAKE_SOURCE_DIR}/script/${USE_LEAK_CHECKER}.sh" "${CMAKE_BINARY_DIR}/libgit2_tests" ${ARGN})
+		add_test(${name} "${PROJECT_SOURCE_DIR}/script/${USE_LEAK_CHECKER}.sh" "${PROJECT_BINARY_DIR}/libgit2_tests" ${ARGN})
 	else()
-		add_test(${name} "${CMAKE_BINARY_DIR}/libgit2_tests" ${ARGN})
+		add_test(${name} "${PROJECT_BINARY_DIR}/libgit2_tests" ${ARGN})
 	endif()
 endfunction(ADD_CLAR_TEST)