corresponding targets has the same content but different
@code{ctime}/@code{mtime} values and rewrites dependencies with that
updated inode information.
+@item
+ With @env{$REDO_STOP_IF_MODIFIED=1} environment variable redo will
+ stop and fail if it meet externally modified file. By default user
+ is only warned about it, but building continues for convenience.
@end itemize
@anchor{Release 1_21_0}