pg_combinebackup: Message style improvements

src/bin/pg_combinebackup/copy_file.c

@@ -330,7 +330,7 @@ copy_file_link(const char *src, const char *dest,
 			   pg_checksum_context *checksum_ctx)
 {
 	if (link(src, dest) < 0)
-		pg_fatal("error while linking file from \"%s\" to \"%s\": %m",
+		pg_fatal("could not create link from \"%s\" to \"%s\": %m",
 				 src, dest);
 
 	/* if needed, calculate checksum of the file */

src/bin/pg_combinebackup/pg_combinebackup.c

@@ -432,7 +432,7 @@ main(int argc, char *argv[])
 	/* Warn about the possibility of compromising the backups, when link mode */
 	if (opt.copy_method == COPY_METHOD_LINK)
 		pg_log_warning("--link mode was used; any modifications to the output "
-					   "directory may destructively modify input directories");
+					   "directory might destructively modify input directories");
 
 	/* It's a success, so don't remove the output directories. */
 	reset_directory_cleanup_list();