Move plugins to own package & improve apigen CLI

[sknat]

This patch moves the binapigenerator plugins to their own package.

• It capitalizes the methods they leverage.
• It changes the way plugins are called, passing the whole generator
  at once and letting the plugin themselves loop on the files.
  This allow for more variety in filtering, aggregation, etc...

This patch also proposes an evolution to the binapigen CLI
in order to make it more user-friendly for newcomers as well
as build pipelines based on go:generate

For now two usecases are in the picture:

• Building from a directory containing .json files
  e.g. 'binapigen --api /usr/share/vpp/api --output ./myapp/bindings --filter interface,ip'
• Building from a cloned local VPP
  e.g. 'binapigen --vpp ~/vpp --output ./myapp/binding'

Signed-off-by: Nathan Skrzypczak nathan.skrzypczak@gmail.com
Change-Id: I5b0b2ade40ab80c9e91c2a422f8c193b232d9830

[ondrej-fabry]

Why including quite unrelated changes into here? It would be good to keep this PR only about separating the plugins - making the generator extendable. The changes to the API are not needed for this.

[sknat]

You mean having this patch on top of #28 or the fact that the 62f5161 in itself is too big in your view ?
Regarding the former, I'm keeping those two stacked as we are depending on the combination, and I wanted avoid the perpetual rebase overhead.

[ondrej-fabry]

You mean having this patch on top of #28 or the fact that the 62f5161 in itself is too big in your view ? Regarding the former, I'm keeping those two stacked as we are depending on the combination, and I wanted avoid the perpetual rebase overhead.

I think both. Basically I think a change like this should be done in multiple steps. This helps with doing reviews, bisecting possible issues and makes the changes testable separately.

Overall, I do not see how these changes relate together in GoVPP and I believe these considerations must have priority over dependency/requirements of other projects.

[sknat]

Ok, so I did split this patch & the previous one, we have (in order)

• Rename api Message types ...MessageTypes #66 Rename api Message types ...MessageTypes
• Add GetRetVal fn to ResponseMessage interface #28 Add GetRetVal fn to ResponseMessage interface
• binapigen cli improvements #67 binapigen cli improvements
• Move plugins to their own module #68 Move plugins to their own module

All these patches are on top of each other (it's way easier due to dependencies between each of them), so looking at a PR will include changes in the previous ones until merged & rebased