Specify the behavior of vcpkg.io in Readme.md

[paul-michalik]

No description provided.

[ras0219-msft]

Let me know how/if we can help upstream :) I wouldn't be opposed to adding some lower level commands if they would be useful.

[paul-michalik]

Oh yeah, I will!

The idea is described in the Readme on the feature branch. Basically, we want to add a level of indirection which tries to "download and import" pre-built packages matching a specific revision of vcpkg repo before brewing... The opposite direction - "export and upload" - should also be supported.

Current upstream supports the "export" part to some extent. In our experiment we use the output of "vcpkg export --dry-run" and the content of the exported .list files to collect the artifacts. The opposite "vcpkg import" command exists but it's not really clear to me what it does. I filed a request for documenting this. If there was a "import --raw" command which acts as the opposite of "export --raw" things would be very easy.

In the end, I assume this should be doable by few invocations of vcpkg, git and robocopy plus minimal PowerShell, mainly for web requests.