doc: clarify that git_time_t is seconds from the epoch

include/git2/signature.h

@@ -30,8 +30,8 @@ GIT_BEGIN_DECL
  * @param out new signature, in case of error NULL
  * @param name name of the person
  * @param email email of the person
- * @param time time when the action happened
- * @param offset timezone offset in minutes for the time
+ * @param time time (in seconds from epoch) when the action happened
+ * @param offset timezone offset (in minutes) for the time
  * @return 0 or an error code
  */
 GIT_EXTERN(int) git_signature_new(git_signature **out, const char *name, const char *email, git_time_t time, int offset);

include/git2/types.h

@@ -59,7 +59,7 @@ typedef __haiku_std_int64 git_time_t;
  * app, even though /we/ define _FILE_OFFSET_BITS=64.
  */
 typedef int64_t git_off_t;
-typedef int64_t git_time_t;
+typedef int64_t git_time_t; /**< time in seconds from epoch */
 
 #endif