hash: use CommonCrypto on OSX for SHA-1

OSX has its own cryptographic library, let's make use of it instead of
calling out to OpenSSL.

CMakeLists.txt

@@ -41,6 +41,7 @@ OPTION( VALGRIND			"Configure build for valgrind"			OFF )
 
 IF(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
 	SET( USE_ICONV ON )
+	ADD_DEFINITIONS(-DGIT_COMMON_CRYPTO)
 ENDIF()
 
 IF(MSVC)

src/hash.h

@@ -16,7 +16,9 @@ int git_hash_global_init(void);
 int git_hash_ctx_init(git_hash_ctx *ctx);
 void git_hash_ctx_cleanup(git_hash_ctx *ctx);
 
-#if defined(OPENSSL_SHA1)
+#if defined(GIT_COMMON_CRYPTO)
+# include "hash/hash_common_crypto.h"
+#elif defined(OPENSSL_SHA1)
 # include "hash/hash_openssl.h"
 #elif defined(WIN32_SHA1)
 # include "hash/hash_win32.h"

src/hash/hash_common_crypto.h

+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#ifndef INCLUDE_hash_common_crypto_h__
+#define INCLUDE_hash_common_crypto_h__
+
+#include "hash.h"
+
+#include <CommonCrypto/CommonDigest.h>
+
+struct git_hash_ctx {
+	CC_SHA1_CTX c;
+};
+
+#define git_hash_global_init() 0
+#define git_hash_ctx_init(ctx) git_hash_init(ctx)
+#define git_hash_ctx_cleanup(ctx)
+
+GIT_INLINE(int) git_hash_init(git_hash_ctx *ctx)
+{
+	assert(ctx);
+	CC_SHA1_Init(&ctx->c);
+	return 0;
+}
+
+GIT_INLINE(int) git_hash_update(git_hash_ctx *ctx, const void *data, size_t len)
+{
+	assert(ctx);
+	CC_SHA1_Update(&ctx->c, data, len);
+	return 0;
+}
+
+GIT_INLINE(int) git_hash_final(git_oid *out, git_hash_ctx *ctx)
+{
+	assert(ctx);
+	CC_SHA1_Final(out->id, &ctx->c);
+	return 0;
+}
+
+#endif /* INCLUDE_hash_common_crypto_h__ */