Log a note at program start when running in dry-run mode

Users might get some peace of mind knowing their data is not being
destroyed or whatever.

Author: Peter Smith <smithpb2250@gmail.com>
Reviewed-by: Álvaro Herrera <alvherre@kurilemu.de>
Discussion: https://postgr.es/m/CAHut+PsvQJQnQO0KT0S2oegenkvJ8FUuY-QS5syyqmT24R2xFQ@mail.gmail.com

src/bin/pg_archivecleanup/pg_archivecleanup.c

@@ -375,6 +375,10 @@ main(int argc, char **argv)
 		exit(2);
 	}
 
+	if (dryrun)
+		pg_log_info("Executing in dry-run mode.\n"
+					"No files will be removed.");
+
 	/*
 	 * Check archive exists and other initialization if required.
 	 */

src/bin/pg_basebackup/pg_createsubscriber.c

@@ -2305,6 +2305,11 @@ main(int argc, char **argv)
 		pg_log_error_hint("Try \"%s --help\" for more information.", progname);
 		exit(1);
 	}
+
+	if (dry_run)
+		pg_log_info("Executing in dry-run mode.\n"
+					"The target directory will not be modified.");
+
 	pg_log_info("validating publisher connection string");
 	pub_base_conninfo = get_base_conninfo(opt.pub_conninfo_str,
 										  &dbname_conninfo);

src/bin/pg_combinebackup/pg_combinebackup.c

@@ -242,6 +242,10 @@ main(int argc, char *argv[])
 	if (opt.no_manifest)
 		opt.manifest_checksums = CHECKSUM_TYPE_NONE;
 
+	if (opt.dry_run)
+		pg_log_info("Executing in dry-run mode.\n"
+					"The target directory will not be modified.");
+
 	/* Check that the platform supports the requested copy method. */
 	if (opt.copy_method == COPY_METHOD_CLONE)
 	{

src/bin/pg_rewind/pg_rewind.c

@@ -300,10 +300,12 @@ main(int argc, char **argv)
 
 	atexit(disconnect_atexit);
 
-	/*
-	 * Ok, we have all the options and we're ready to start. First, connect to
-	 * remote server.
-	 */
+	/* Ok, we have all the options and we're ready to start. */
+	if (dry_run)
+		pg_log_info("Executing in dry-run mode.\n"
+					"The target directory will not be modified.");
+
+	/* First, connect to remote server. */
 	if (connstr_source)
 	{
 		conn = PQconnectdb(connstr_source);