be able to diff across forks

In the wonderful elm package manager
there is a diff function.
If you installed a fork of a module, and the original module, lets say
elm-community/typed-svg and canadaduane/typed-svg you want to be able to diff across the forks with elm-package

Running an import with both installed gives you :

I found multiple modules named 'TypedSvg'.
Module 'Main' is trying to import it.
Modules with that name were found in the following locations:
    package canadaduane/typed-svg
    package elm-community/typed-svg

So trying to diff the two does not work :
elm-package diff canadaduane/typed-svg elm-community/typed-svg

give the message :

Uh oh, argument "elm-community/typed-svg" is not a valid VERSION

Copying the version into the other and running diff does not help

cp -vr elm-stuff/packages/canadaduane/typed-svg/2.1.1/ elm-stuff/packages/elm-community/typed-svg/
elm-package diff elm-community/typed-svg 2.1.1 2.0.0
Comparing elm-community/typed-svg 2.1.1 to 2.0.0...
Error: The following HTTP request failed.
<http://package.elm-lang.org/documentation?elm-package-version=0.18&name=elm-community%2Ftyped-svg&version=2.1.1>
That library and version is not registered.

Now diffing the same module from the version that I guess at does work but still does not tell me if the baseline 2.0.0 is identical.

elm-package diff canadaduane/typed-svg 2.0.0  2.1.1
Comparing canadaduane/typed-svg 2.0.0 to 2.1.1...
This is a MINOR change.
------ Added modules - MINOR ------
    TypedSvg.Attributes.InEm
    TypedSvg.Attributes.InPx
    TypedSvg.Extra.InPx

Also the straight file diff gives me irrelevant changes

diff -d -w -r elm-stuff/packages/canadaduane/typed-svg/2.1.1/ elm-stuff/packages/elm-community/typed-svg/2.0.0/

So what I am looking for is a diff tool for elm that does the following :

1. compare across forks.
2. compare apis
3. compares the canonical pretty-printed formatted source code
4. compares documentation in canonical html/markdown form that would resolve differences like this, because they both resolve to the same url

< See: https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/scale
---
> See: <https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/scale>
> 

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Posted on Utopian.io - Rewarding Open Source Contributors

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