filter: return on null filter from open and close

So that we don't have to include the if(filter) open_filter(filter)
block everywhere, we introduce the guard in the function itself. This
should simplify quite a bit of code.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

filter.c

@@ -351,6 +351,8 @@ int cgit_open_filter(struct cgit_filter *filter, ...)
 {
 	int result;
 	va_list ap;
+	if (!filter)
+		return 0;
 	va_start(ap, filter);
 	result = filter->open(filter, ap);
 	va_end(ap);
@@ -359,6 +361,8 @@ int cgit_open_filter(struct cgit_filter *filter, ...)
 
 int cgit_close_filter(struct cgit_filter *filter)
 {
+	if (!filter)
+		return 0;
 	return filter->close(filter);
 }
 

ui-commit.c

@@ -107,27 +107,21 @@ void cgit_print_commit(char *hex, const char *prefix)
 	}
 	html("</table>\n");
 	html("<div class='commit-subject'>");
-	if (ctx.repo->commit_filter)
 	cgit_open_filter(ctx.repo->commit_filter);
 	html_txt(info->subject);
-	if (ctx.repo->commit_filter)
 	cgit_close_filter(ctx.repo->commit_filter);
 	show_commit_decorations(commit);
 	html("</div>");
 	html("<div class='commit-msg'>");
-	if (ctx.repo->commit_filter)
 	cgit_open_filter(ctx.repo->commit_filter);
 	html_txt(info->msg);
-	if (ctx.repo->commit_filter)
 	cgit_close_filter(ctx.repo->commit_filter);
 	html("</div>");
 	if (notes.len != 0) {
 		html("<div class='notes-header'>Notes</div>");
 		html("<div class='notes'>");
-		if (ctx.repo->commit_filter)
 		cgit_open_filter(ctx.repo->commit_filter);
 		html_txt(notes.buf);
-		if (ctx.repo->commit_filter)
 		cgit_close_filter(ctx.repo->commit_filter);
 		html("</div>");
 		html("<div class='notes-footer'></div>");

ui-repolist.c

@@ -333,9 +333,7 @@ void cgit_print_site_readme()
 {
 	if (!ctx.cfg.root_readme)
 		return;
-	if (ctx.cfg.about_filter)
 	cgit_open_filter(ctx.cfg.about_filter, ctx.cfg.root_readme);
 	html_include(ctx.cfg.root_readme);
-	if (ctx.cfg.about_filter)
 	cgit_close_filter(ctx.cfg.about_filter);
 }

ui-summary.c

@@ -151,15 +151,11 @@ void cgit_print_repo_readme(char *path)
 	 * filesystem, while applying the about-filter.
 	 */
 	html("<div id='summary'>");
-	if (ctx.repo->about_filter)
 	cgit_open_filter(ctx.repo->about_filter, filename);
-
 	if (ref)
 		cgit_print_file(filename, ref, 1);
 	else
 		html_include(filename);
-
-	if (ctx.repo->about_filter)
 	cgit_close_filter(ctx.repo->about_filter);
 
 	html("</div>");