trace: suffix the callbacks with `_cb`

The trace logging callbacks should match the other callback naming
conventions, using the `_cb` suffix instead of a `_callback` suffix.

include/git2/deprecated.h

@@ -14,6 +14,7 @@
 #include "object.h"
 #include "refs.h"
 #include "remote.h"
+#include "trace.h"
 
 /*
  * Users can avoid deprecated functions by defining `GIT_DEPRECATE_HARD`.
@@ -261,6 +262,20 @@ typedef git_cred_ssh_interactive_cb git_cred_ssh_interactive_callback;
 
 /**@}*/
 
+/** @name Deprecated Trace Callback Types
+ *
+ * These types are retained for backward compatibility.  The newer
+ * versions of these values should be preferred in all new code.
+ *
+ * There is no plan to remove these backward compatibility values at
+ * this time.
+ */
+/**@{*/
+
+typedef git_trace_cb git_trace_callback;
+
+/**@}*/
+
 /** @name Deprecated Transfer Progress Types
  *
  * These types are retained for backward compatibility.  The newer

include/git2/trace.h

@@ -49,7 +49,7 @@ typedef enum {
 /**
  * An instance for a tracing function
  */
-typedef void GIT_CALLBACK(git_trace_callback)(git_trace_level_t level, const char *msg);
+typedef void GIT_CALLBACK(git_trace_cb)(git_trace_level_t level, const char *msg);
 
 /**
  * Sets the system tracing configuration to the specified level with the
@@ -60,7 +60,7 @@ typedef void GIT_CALLBACK(git_trace_callback)(git_trace_level_t level, const cha
  * @param cb Function to call with trace data
  * @return 0 or an error code
  */
-GIT_EXTERN(int) git_trace_set(git_trace_level_t level, git_trace_callback cb);
+GIT_EXTERN(int) git_trace_set(git_trace_level_t level, git_trace_cb cb);
 
 /** @} */
 GIT_END_DECL

src/trace.c

@@ -17,7 +17,7 @@ struct git_trace_data git_trace__data = {0};
 
 #endif
 
-int git_trace_set(git_trace_level_t level, git_trace_callback callback)
+int git_trace_set(git_trace_level_t level, git_trace_cb callback)
 {
 #ifdef GIT_TRACE
 	assert(level == 0 || callback != NULL);

src/trace.h

@@ -16,7 +16,7 @@
 
 struct git_trace_data {
 	git_trace_level_t level;
-	git_trace_callback callback;
+	git_trace_cb callback;
 };
 
 extern struct git_trace_data git_trace__data;
@@ -25,7 +25,7 @@ GIT_INLINE(void) git_trace__write_fmt(
 	git_trace_level_t level,
 	const char *fmt, ...)
 {
-	git_trace_callback callback = git_trace__data.callback;
+	git_trace_cb callback = git_trace__data.callback;
 	git_buf message = GIT_BUF_INIT;
 	va_list ap;