show_log: factor out interdiff/range-diff generation

The integration of "git range-diff" with "git format-patch" for a
single patch (i.e., not generating "range-diff" into the cover
letter) hooks into log-tree.c:show_log(), which is responsible for
writing the log message out and other stuff.  Essentially,
everything you see before the diffstat and the patch is generated
there.

Split out the code that spits out the interdiff/range-diff into a
separate helper function show_diff_of_diff().  Hopefully this will
make it easier to move things around in the output stream in the
future patches.

This is supposed to be a no-op refactoring.

Signed-off-by: Junio C Hamano <[email protected]>

Author: gitster

log-tree.c

@@ -673,6 +673,53 @@ static void next_commentary_block(struct rev_info *opt, struct strbuf *sb)
 	opt->shown_dashes = 1;
 }
 
+static void show_diff_of_diff(struct rev_info *opt)
+{
+	if (!cmit_fmt_is_mail(opt->commit_format))
+		return;
+
+	if (opt->idiff_oid1) {
+		struct diff_queue_struct dq;
+
+		memcpy(&dq, &diff_queued_diff, sizeof(diff_queued_diff));
+		DIFF_QUEUE_CLEAR(&diff_queued_diff);
+
+		next_commentary_block(opt, NULL);
+		fprintf_ln(opt->diffopt.file, "%s", opt->idiff_title);
+		show_interdiff(opt->idiff_oid1, opt->idiff_oid2, 2,
+			       &opt->diffopt);
+
+		memcpy(&diff_queued_diff, &dq, sizeof(diff_queued_diff));
+	}
+
+	if (opt->rdiff1) {
+		struct diff_queue_struct dq;
+		struct diff_options opts;
+		struct range_diff_options range_diff_opts = {
+			.creation_factor = opt->creation_factor,
+			.dual_color = 1,
+			.diffopt = &opts
+		};
+
+		memcpy(&dq, &diff_queued_diff, sizeof(diff_queued_diff));
+		DIFF_QUEUE_CLEAR(&diff_queued_diff);
+
+		next_commentary_block(opt, NULL);
+		fprintf_ln(opt->diffopt.file, "%s", opt->rdiff_title);
+		/*
+		 * Pass minimum required diff-options to range-diff; others
+		 * can be added later if deemed desirable.
+		 */
+		repo_diff_setup(the_repository, &opts);
+		opts.file = opt->diffopt.file;
+		opts.use_color = opt->diffopt.use_color;
+		diff_setup_done(&opts);
+		show_range_diff(opt->rdiff1, opt->rdiff2, &range_diff_opts);
+
+		memcpy(&diff_queued_diff, &dq, sizeof(diff_queued_diff));
+	}
+}
+
 void show_log(struct rev_info *opt)
 {
 	struct strbuf msgbuf = STRBUF_INIT;
@@ -857,46 +904,7 @@ void show_log(struct rev_info *opt)
 	free(ctx.notes_message);
 	free(ctx.after_subject);
 
-	if (cmit_fmt_is_mail(ctx.fmt) && opt->idiff_oid1) {
-		struct diff_queue_struct dq;
-
-		memcpy(&dq, &diff_queued_diff, sizeof(diff_queued_diff));
-		DIFF_QUEUE_CLEAR(&diff_queued_diff);
-
-		next_commentary_block(opt, NULL);
-		fprintf_ln(opt->diffopt.file, "%s", opt->idiff_title);
-		show_interdiff(opt->idiff_oid1, opt->idiff_oid2, 2,
-			       &opt->diffopt);
-
-		memcpy(&diff_queued_diff, &dq, sizeof(diff_queued_diff));
-	}
-
-	if (cmit_fmt_is_mail(ctx.fmt) && opt->rdiff1) {
-		struct diff_queue_struct dq;
-		struct diff_options opts;
-		struct range_diff_options range_diff_opts = {
-			.creation_factor = opt->creation_factor,
-			.dual_color = 1,
-			.diffopt = &opts
-		};
-
-		memcpy(&dq, &diff_queued_diff, sizeof(diff_queued_diff));
-		DIFF_QUEUE_CLEAR(&diff_queued_diff);
-
-		next_commentary_block(opt, NULL);
-		fprintf_ln(opt->diffopt.file, "%s", opt->rdiff_title);
-		/*
-		 * Pass minimum required diff-options to range-diff; others
-		 * can be added later if deemed desirable.
-		 */
-		repo_diff_setup(the_repository, &opts);
-		opts.file = opt->diffopt.file;
-		opts.use_color = opt->diffopt.use_color;
-		diff_setup_done(&opts);
-		show_range_diff(opt->rdiff1, opt->rdiff2, &range_diff_opts);
-
-		memcpy(&diff_queued_diff, &dq, sizeof(diff_queued_diff));
-	}
+	show_diff_of_diff(opt);
 }
 
 int log_tree_diff_flush(struct rev_info *opt)