deprecation: add used attribute

ethomson · ethomson · commit 44827b6764da · 2019-01-20T10:36:41.000Z
Recent GCC enables `-Wunused-const-variables`, which makes output quite
noisy.  Disable unused warnings for our deprecated variables.
diff --git a/include/git2/common.h b/include/git2/common.h
@@ -59,6 +59,7 @@ typedef size_t size_t;
 #if defined(__GNUC__)
 # define GIT_DEPRECATED(func) \
 			 __attribute__((deprecated)) \
+			 __attribute__((used)) \
 			 func
 #elif defined(_MSC_VER)
 # define GIT_DEPRECATED(func) __declspec(deprecated) func
