RFC: Adding support for an API-"since"-version-attribute to Haddock?

[Herbert Valerio Riedel]

Hello Haskellers,

I've been wondering whether it might be useful to add a feature to
Haddock similar to what can be found in other API documentation systems,
specifically an optional parseable "since"-attribute, declaring the last
package version when the associated definition/symbol was introduced or
its semantics modified.

Beyond giving a uniform/standard representation for this kind of
information (e.g. if Haddock would render this information in a
distinctive style suitable to give a visual hint for locating this
information easily), this information could be used to generate an
automated changelog entry (at least for the current package version),
listing all definitions added or modified with the current version.

Another application I could thinkg of would be to find the lowest
version of a package supporting the currently used API from it (given
the currently known-to-work package-version and a list of currently used
symbols from that package).

Would such an enhancement to Haddock be worthwhile or is it a bad idea?
Has such a proposal come up in the past already? Are there alternative
approaches to consider?