cmake: refactor regex selection

Move regex selection into its own cmake module.

cmake/SelectRegex.cmake

+# Specify regular expression implementation
+find_package(PCRE)
+
+if(REGEX_BACKEND STREQUAL "")
+	check_symbol_exists(regcomp_l "regex.h;xlocale.h" HAVE_REGCOMP_L)
+
+	if(HAVE_REGCOMP_L)
+		set(REGEX_BACKEND "regcomp_l")
+	elseif(PCRE_FOUND)
+		set(REGEX_BACKEND "pcre")
+	else()
+		set(REGEX_BACKEND "builtin")
+	endif()
+endif()
+
+if(REGEX_BACKEND STREQUAL "regcomp_l")
+	add_feature_info(regex ON "using system regcomp_l")
+	set(GIT_REGEX_REGCOMP_L 1)
+elseif(REGEX_BACKEND STREQUAL "pcre2")
+	find_package(PCRE2)
+
+	if(NOT PCRE2_FOUND)
+		MESSAGE(FATAL_ERROR "PCRE2 support was requested but not found")
+	endif()
+
+	add_feature_info(regex ON "using system PCRE2")
+	set(GIT_REGEX_PCRE2 1)
+
+	list(APPEND LIBGIT2_SYSTEM_INCLUDES ${PCRE2_INCLUDE_DIRS})
+	list(APPEND LIBGIT2_LIBS ${PCRE2_LIBRARIES})
+	list(APPEND LIBGIT2_PC_REQUIRES "libpcre2-8")
+elseif(REGEX_BACKEND STREQUAL "pcre")
+	add_feature_info(regex ON "using system PCRE")
+	set(GIT_REGEX_PCRE 1)
+
+	list(APPEND LIBGIT2_SYSTEM_INCLUDES ${PCRE_INCLUDE_DIRS})
+	list(APPEND LIBGIT2_LIBS ${PCRE_LIBRARIES})
+	list(APPEND LIBGIT2_PC_REQUIRES "libpcre")
+elseif(REGEX_BACKEND STREQUAL "regcomp")
+	add_feature_info(regex ON "using system regcomp")
+	set(GIT_REGEX_REGCOMP 1)
+elseif(REGEX_BACKEND STREQUAL "builtin")
+	add_feature_info(regex ON "using bundled PCRE")
+	set(GIT_REGEX_BUILTIN 1)
+
+	add_subdirectory("${libgit2_SOURCE_DIR}/deps/pcre" "${libgit2_BINARY_DIR}/deps/pcre")
+	list(APPEND LIBGIT2_INCLUDES "${libgit2_SOURCE_DIR}/deps/pcre")
+	list(APPEND LIBGIT2_OBJECTS $<TARGET_OBJECTS:pcre>)
+else()
+	message(FATAL_ERROR "The REGEX_BACKEND option provided is not supported")
+endif()

src/CMakeLists.txt

@@ -114,61 +114,10 @@ endif()
 include(SelectHTTPSBackend)
 include(SelectHashes)
 include(SelectHTTPParser)
+include(SelectRegex)
 
 target_sources(git2internal PRIVATE ${SRC_SHA1})
 
-# Specify regular expression implementation
-find_package(PCRE)
-
-if(REGEX_BACKEND STREQUAL "")
-	check_symbol_exists(regcomp_l "regex.h;xlocale.h" HAVE_REGCOMP_L)
-
-	if(HAVE_REGCOMP_L)
-		set(REGEX_BACKEND "regcomp_l")
-	elseif(PCRE_FOUND)
-		set(REGEX_BACKEND "pcre")
-	else()
-		set(REGEX_BACKEND "builtin")
-	endif()
-endif()
-
-if(REGEX_BACKEND STREQUAL "regcomp_l")
-	add_feature_info(regex ON "using system regcomp_l")
-	set(GIT_REGEX_REGCOMP_L 1)
-elseif(REGEX_BACKEND STREQUAL "pcre2")
-	find_package(PCRE2)
-
-	if(NOT PCRE2_FOUND)
-		MESSAGE(FATAL_ERROR "PCRE2 support was requested but not found")
-	endif()
-
-	add_feature_info(regex ON "using system PCRE2")
-	set(GIT_REGEX_PCRE2 1)
-
-	list(APPEND LIBGIT2_SYSTEM_INCLUDES ${PCRE2_INCLUDE_DIRS})
-	list(APPEND LIBGIT2_LIBS ${PCRE2_LIBRARIES})
-	list(APPEND LIBGIT2_PC_REQUIRES "libpcre2-8")
-elseif(REGEX_BACKEND STREQUAL "pcre")
-	add_feature_info(regex ON "using system PCRE")
-	set(GIT_REGEX_PCRE 1)
-
-	list(APPEND LIBGIT2_SYSTEM_INCLUDES ${PCRE_INCLUDE_DIRS})
-	list(APPEND LIBGIT2_LIBS ${PCRE_LIBRARIES})
-	list(APPEND LIBGIT2_PC_REQUIRES "libpcre")
-elseif(REGEX_BACKEND STREQUAL "regcomp")
-	add_feature_info(regex ON "using system regcomp")
-	set(GIT_REGEX_REGCOMP 1)
-elseif(REGEX_BACKEND STREQUAL "builtin")
-	add_feature_info(regex ON "using bundled PCRE")
-	set(GIT_REGEX_BUILTIN 1)
-
-	add_subdirectory("${libgit2_SOURCE_DIR}/deps/pcre" "${libgit2_BINARY_DIR}/deps/pcre")
-	list(APPEND LIBGIT2_INCLUDES "${libgit2_SOURCE_DIR}/deps/pcre")
-	list(APPEND LIBGIT2_OBJECTS $<TARGET_OBJECTS:pcre>)
-else()
-	message(FATAL_ERROR "The REGEX_BACKEND option provided is not supported")
-endif()
-
 # Optional external dependency: zlib
 SanitizeBool(USE_BUNDLED_ZLIB)
 if(USE_BUNDLED_ZLIB STREQUAL ON)