+@option{-log-pid} (@env{$REDO_LOG_PID=1}) can be used to prefix job's
+@code{stderr} with the PID, that could be useful during parallel builds.
+@option{-d} (@env{$REDO_DEBUG=1}) enables debug messages.
+
+@option{-no-progress} (@env{$REDO_NO_PROGRESS=1}) and
+@option{-no-status} (@env{$REDO_NO_STATUS=1}) disable statusline and
+progress display. @env{$NO_COLOR=1} disables progress/debug messages
+colouring.
+
+By default all build commands use @code{fsync} to assure data is reached
+the disk. You can disable its usage with @env{$REDO_NO_SYNC=1}
+environment variable, for speeding up the build process.
+
+@command{goredo} determines target is out-of-date by comparing its size,
+@code{ctime} and content's hash, if @code{ctime} differs. Depending on
+the filesystem you use, probably you can not trust its @code{ctime}
+value at all. In that case you can set @env{$REDO_INODE_NO_TRUST=1} to
+forcefully verify the hash.