thodg/libgit2

diff --git a/.travis.yml b/.travis.yml
index a8e31a0..8bbcb39 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -18,8 +18,8 @@ env:
   - secure: "YnhS+8n6B+uoyaYfaJ3Lei7cSJqHDPiKJCKFIF2c87YDfmCvAJke8QtE7IzjYDs7UFkTCM4ox+ph2bERUrxZbSCyEkHdjIZpKuMJfYWja/jgMqTMxdyOH9y8JLFbZsSXDIXDwqBlC6vVyl1fP90M35wuWcNTs6tctfVWVofEFbs="
   - GITTEST_INVASIVE_FS_SIZE=1
  matrix:
-  - OPTIONS="-DTHREADSAFE=ON -DCMAKE_BUILD_TYPE=Release"
-  - OPTIONS="-DTHREADSAFE=OFF -DBUILD_EXAMPLES=ON"
+  - OPTIONS="-DTHREADSAFE=ON -DCMAKE_BUILD_TYPE=Release -DENABLE_WERROR=ON"
+  - OPTIONS="-DTHREADSAFE=OFF -DBUILD_EXAMPLES=ON -DENABLE_WERROR=ON"
 
 dist: trusty
 sudo: true
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1a9436f..4c03aa0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -49,6 +49,7 @@ OPTION( VALGRIND			"Configure build for valgrind"			OFF )
 OPTION( CURL			"Use curl for HTTP if available" ON)
 OPTION( USE_EXT_HTTP_PARSER		"Use system HTTP_Parser if available" ON)
 OPTION( DEBUG_POOL			"Enable debug pool allocator"			OFF )
+OPTION( ENABLE_WERROR			"Enable compilation with -Werror"		OFF )
 
 IF(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
 	SET( USE_ICONV ON )
@@ -223,8 +224,23 @@ IF (MSVC)
 ELSE ()
 	SET(CMAKE_C_FLAGS "-D_GNU_SOURCE ${CMAKE_C_FLAGS}")
 
-	ADD_C_FLAG_IF_SUPPORTED(-Wall)
-	ADD_C_FLAG_IF_SUPPORTED(-Wextra)
+	MACRO(ENABLE_WARNINGS flag)
+		IF(ENABLE_WERROR)
+			ADD_C_FLAG_IF_SUPPORTED(-Werror=${flag})
+		ELSE()
+			ADD_C_FLAG_IF_SUPPORTED(-W${flag})
+		ENDIF()
+	ENDMACRO()
+
+	MACRO(DISABLE_WARNINGS flag)
+		ADD_C_FLAG_IF_SUPPORTED(-Wno-${flag})
+		IF(ENABLE_WERROR)
+			ADD_C_FLAG_IF_SUPPORTED(-Wno-error=${flag})
+		ENDIF()
+	ENDMACRO()
+
+	ENABLE_WARNINGS(all)
+	ENABLE_WARNINGS(extra)
 
 	IF (CMAKE_SYSTEM_NAME MATCHES "(Solaris|SunOS)")
 		SET(CMAKE_C_FLAGS "-std=c99 -D_POSIX_C_SOURCE=200112L -D__EXTENSIONS__ -D_POSIX_PTHREAD_SEMANTICS ${CMAKE_C_FLAGS}")
@@ -247,16 +263,16 @@ ELSE ()
 		ADD_DEFINITIONS(-D__USE_MINGW_ANSI_STDIO=1)
 	ENDIF ()
 
-	ADD_C_FLAG_IF_SUPPORTED(-Wdocumentation)
-	ADD_C_FLAG_IF_SUPPORTED(-Wno-missing-field-initializers)
-	ADD_C_FLAG_IF_SUPPORTED(-Wstrict-aliasing=2)
-	ADD_C_FLAG_IF_SUPPORTED(-Wstrict-prototypes)
-	ADD_C_FLAG_IF_SUPPORTED(-Wdeclaration-after-statement)
-	ADD_C_FLAG_IF_SUPPORTED(-Wno-unused-const-variable)
-	ADD_C_FLAG_IF_SUPPORTED(-Wno-unused-function)
+	ENABLE_WARNINGS(documentation)
+	DISABLE_WARNINGS(missing-field-initializers)
+	ENABLE_WARNINGS(strict-aliasing=2)
+	ENABLE_WARNINGS(strict-prototypes)
+	ENABLE_WARNINGS(declaration-after-statement)
+	DISABLE_WARNINGS(unused-const-variable)
+	DISABLE_WARNINGS(unused-function)
 
 	IF (APPLE) # Apple deprecated OpenSSL
-		ADD_C_FLAG_IF_SUPPORTED(-Wno-deprecated-declarations)
+	    DISABLE_WARNINGS(deprecated-declarations)
 	ENDIF()
 
 	IF (PROFILE)