factor out BARF_UNLESS_COPYABLE

Move the common basic element type check of COPY_ARRAY and MOVE_ARRAY to
a new macro.  This reduces code duplication and simplifies adding more
elaborate checks.

Suggested-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-compat-util.h

@@ -1093,8 +1093,11 @@ int xstrncmpz(const char *s, const char *t, size_t len);
 #define CALLOC_ARRAY(x, alloc) (x) = xcalloc((alloc), sizeof(*(x)))
 #define REALLOC_ARRAY(x, alloc) (x) = xrealloc((x), st_mult(sizeof(*(x)), (alloc)))
 
+#define BARF_UNLESS_COPYABLE(dst, src) \
+	BUILD_ASSERT_OR_ZERO(sizeof(*(dst)) == sizeof(*(src)))
+
 #define COPY_ARRAY(dst, src, n) copy_array((dst), (src), (n), sizeof(*(dst)) + \
-	BUILD_ASSERT_OR_ZERO(sizeof(*(dst)) == sizeof(*(src))))
+	BARF_UNLESS_COPYABLE((dst), (src)))
 static inline void copy_array(void *dst, const void *src, size_t n, size_t size)
 {
 	if (n)
@@ -1102,7 +1105,7 @@ static inline void copy_array(void *dst, const void *src, size_t n, size_t size)
 }
 
 #define MOVE_ARRAY(dst, src, n) move_array((dst), (src), (n), sizeof(*(dst)) + \
-	BUILD_ASSERT_OR_ZERO(sizeof(*(dst)) == sizeof(*(src))))
+	BARF_UNLESS_COPYABLE((dst), (src)))
 static inline void move_array(void *dst, const void *src, size_t n, size_t size)
 {
 	if (n)