feat(*): compare two concerto models (contributes to #442)

[sstone1]

Introduce a new API and CLI command that allows you to compare two versions of the same model to determine how compatible your changes are, so that you can make a decision of how to increment the version. Breaking changes should result in major version changes, and compatible changes should result in minor or patch version changes.

CLI examples:

% concerto compare --old compare-a.cto --new compare-b.cto
[required-field-added]: The required field "flag" was added to the concept "Thing" (major)

overall result: major

% concerto compare --old compare-b.cto --new compare-c.cto
[optional-field-added]: The optional field "number" was added to the concept "Thing" (patch)

overall result: patch

% concerto compare --old compare-a.cto --new compare-c.cto
[required-field-added]: The required field "flag" was added to the concept "Thing" (major)
[optional-field-added]: The optional field "number" was added to the concept "Thing" (patch)

overall result: major

There's a lot more work to be done to fully find all the differences; the following differences are identified so far:

• Namespace changed
• Declaration added
• Declaration removed
• Required/optional field added
• Field removed

Signed-off-by: Simon Stone [email protected]

[dselman]

Looks great! I didn't see any tests for enums...