Support diff between two environments

[jessicayuen]

From spec:

ksonnet diff <env-one> [env-two]

Diff should model git’s diff between two commits / branches. In the case of environments, diff will output the changes between the components deployed at the API server located at <env-one> and the API server located at <env-two>. <env-#> is the name of an environment. Environments must be created using ksonnet env add before use.

Examples:
Output the differences in components deployed at remote and local “us-west/dev”.
ksonnet diff us-west/dev

Output the differences in components deployed at remote “us-west/dev” and remote “us-west/prod” environments.
ksonnet diff remote:us-west/dev remote:us-west/prod

Output the differences in components deployed at local “us-west/dev” and remote “us-west/prod” environments.
ksonnet diff local:us-west/dev remote:us-west/prod

[seh]

Does diff elide details like creation time, generation, and other controller-set fields?

[jessicayuen]

Not currently, but we've had conversations regarding excluding certain fields. There's some concerns around the maintainability of this list.

[jessicayuen]

This issue was moved to ksonnet/ksonnet#7