Ordering of rules within the rules file matters: rules are matched from top to bottom and
the first matching rule is used, regardless of whether or not there is a more specific match
later in the file.

-- rules --
dst is ad
attr delete a
attr delete b
attr add for-ad=true
plumb to edit

data is hello, world!
attr add c=NEW
plumb to edit

-- initial --
src: bash
dst: ad
wdir: /home/foo/bar
attrs: a=foo b=bar
ndata: 13
data: hello, world!
-- processed --
src: bash
dst: ad
wdir: /home/foo/bar
attrs: for-ad=true
ndata: 13
data: hello, world!
