cmake: use PROJECT_SOURCE_DIR of CMAKE_SOURCE_DIR

Also applies to *_BINARY_DIR.

This effectively reverts 84083dcc8bd41332ccac9d7b537f3e254d79011c,
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.

5 files changed, 11 insertions, 11 deletions

diff --git a/cmake/IdeSplitSources.cmake b/cmake/IdeSplitSources.cmake
index 9e16cbc5f..4f928ac08 100644
--- a/cmake/IdeSplitSources.cmake
+++ b/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 ${rel})
 					if(rel)
diff --git a/cmake/SelectHTTPParser.cmake b/cmake/SelectHTTPParser.cmake
index ffc897fbc..bb6ef5517 100644
--- a/cmake/SelectHTTPParser.cmake
+++ b/cmake/SelectHTTPParser.cmake
@@ -12,8 +12,8 @@ if(USE_HTTP_PARSER STREQUAL "system")
 	endif()
 else()
 	message(STATUS "http-parser version 2 was not found or disabled; using bundled 3rd-party sources.")
-	add_subdirectory("${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()
diff --git a/cmake/SelectRegex.cmake b/cmake/SelectRegex.cmake
index 88aa156b7..2a3a91b8c 100644
--- a/cmake/SelectRegex.cmake
+++ b/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 $<TARGET_OBJECTS:pcre>)
 else()
 	message(FATAL_ERROR "The REGEX_BACKEND option provided is not supported")
diff --git a/cmake/SelectWinHTTP.cmake b/cmake/SelectWinHTTP.cmake
index 38642e136..96e0bdbae 100644
--- a/cmake/SelectWinHTTP.cmake
+++ b/cmake/SelectWinHTTP.cmake
@@ -4,9 +4,9 @@ if(WIN32 AND USE_WINHTTP)
 	# Since MinGW does not come with headers or an import library for winhttp,
 	# we have to include a private header and generate our own import library
 	if(MINGW)
-		add_subdirectory("${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 "${PROJECT_SOURCE_DIR}/deps/winhttp")
 	else()
 		list(APPEND LIBGIT2_SYSTEM_LIBS "winhttp")
 		list(APPEND LIBGIT2_PC_LIBS "-lwinhttp")
diff --git a/cmake/SelectZlib.cmake b/cmake/SelectZlib.cmake
index 0de1d4a98..fb4361abc 100644
--- a/cmake/SelectZlib.cmake
+++ b/cmake/SelectZlib.cmake
@@ -22,13 +22,13 @@ if(USE_BUNDLED_ZLIB STREQUAL "OFF")
 	endif()
 endif()
 if(USE_BUNDLED_ZLIB STREQUAL "Chromium")
-	add_subdirectory("${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()