It is currently counter-intuitive that something like:
# File '/thing' contents
#SomeSetting WrongValue
# Manifest
__line '/thing' \
--line 'SomeSeting GoodValue' \
--regex '^(#[[:space:]]*)?SomeSetting[[:space:]]'
Produces:
# Resulting '/thing' contents
#SomeSetting WrongValue
This makes sense given the implementation, but it masks a very common use-case.
Changing the default behaviour for such a base type is not really an option, so
instead we add a `replace` as a valid value for `--state`, which would result
in:
# Resulting '/thing' contents with: --state replace
SomeSetting GoodValue
For compatibility, if the regex is missing, `--state replace` behaves just as
`--state present`.