The difference between git whatchanged and log

whatchanged-log.diff

diff --git a/whatchanged b/log
index fa1b223..004d9aa 100644
--- a/tmp/whatchanged
+++ b/tmp/log
@@ -1,4 +1,4 @@
-int cmd_whatchanged(int argc, const char **argv, const char *prefix)
+int cmd_log(int argc, const char **argv, const char *prefix)
 {
        struct rev_info rev;
        struct setup_revision_opt opt;
@@ -7,13 +7,10 @@ int cmd_whatchanged(int argc, const char **argv, const char *prefix)
        git_config(git_log_config, NULL);
 
        init_revisions(&rev, prefix);
-       rev.diff = 1;
-       rev.simplify_history = 0;
+       rev.always_show_header = 1;
        memset(&opt, 0, sizeof(opt));
        opt.def = "HEAD";
        opt.revarg_opt = REVARG_COMMITTISH;
        cmd_log_init(argc, argv, prefix, &rev, &opt);
-       if (!rev.diffopt.output_format)
-               rev.diffopt.output_format = DIFF_FORMAT_RAW;
        return cmd_log_walk(&rev);
 }