clone: re-add a way to ignore certificate errors

This used to be done via transport flags, which was removed in a
previous commit.

include/git2/clone.h

@@ -63,6 +63,7 @@ typedef struct git_clone_options {
 
 	git_checkout_opts checkout_opts;
 	int bare;
+	int ignore_cert_errors;
 
 	git_remote_callbacks *remote_callbacks;
 	const char* checkout_branch;

src/clone.c

@@ -310,6 +310,9 @@ static int create_and_configure_origin(
 	if ((error = git_remote_create(&origin, repo, "origin", url)) < 0)
 		goto on_error;
 
+	if (options->ignore_cert_errors)
+		git_remote_check_cert(origin, 0);
+
 	if (options->remote_callbacks &&
 	    (error = git_remote_set_callbacks(origin, options->remote_callbacks)) < 0)
 		goto on_error;