[PATCH] git-compat-util.h: fix build on gcc 4.4.x and earlier

[Jeremy Lin <jeremy.lin@gmail.com>]

Commit 9ff7eb8c88 uses the `deprecated` attribute to display a warning
message when something that is supposed to be unused is actually used.
However, `deprecated` only supports messages starting in gcc 4.5.0, so
earlier versions of gcc end up bailing out with a message like

  error: wrong number of arguments specified for ‘deprecated’ attribute

This commit removes the use of the `deprecated` attribute for gcc 4.4.x
and earlier. As this is just a diagnostic feature for developers, and
presumably very few people are developing on such old systems anyway,
this change shouldn't really impact anyone.

Signed-off-by: Jeremy Lin <jeremy.lin@gmail.com>
---
 git-compat-util.h | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/git-compat-util.h b/git-compat-util.h
index b90b64718e..9e2969edd6 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -190,8 +190,13 @@ struct strbuf;
 #define _SGI_SOURCE 1
 
 #if defined(__GNUC__)
-#define UNUSED __attribute__((unused)) \
+/* The `deprecated` attribute only accepts a message starting in gcc 4.5.0. */
+# if (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__) >= 40500
+#  define UNUSED __attribute__((unused)) \
 	__attribute__((deprecated ("parameter declared as UNUSED")))
+# else
+#  define UNUSED __attribute__((unused))
+# endif
 #else
 #define UNUSED
 #endif
-- 
2.34.1