--- /dev/null
+@node Notes
+@unnumbered Implementation notes
+
+@itemize
+
+@item @file{all} target is default
+@item @file{stdout} is always captured, but no target is created if it
+ was empty
+@item empty targets are considered always out of date
+@item @file{.do}'s @file{$3} is relative path to the file in target directory
+@item @file{.do} search goes up to @file{/} by default, but can be
+ limited with either @env{$REDO_TOP_DIR} environment variable, or by
+ having @file{.redo/top} file in it
+@item target's completion messages are written after they finish
+@item executable @file{.do} is run as is, non-executable is run with
+ @code{/bin/sh -e[x]}
+@item tracing (-x) can be obviously done only for non-executable @file{.do}
+@item parallizable build is done only during @command{redo-ifchange} for
+ human convenience: you can globally enable @env{REDO_JOBS}, but
+ still do for example: @code{redo htmls infos index upload}
+
+@end itemize