md: Support includecode tags

[googlecodelabs]

md: Support includecode tags

[x1ddos]

Sounds like a good feature to have, especially if it's compatible with existing devsite.

Just for a reference, we already support something similar in google docs but it's different, where a fragment import can contain any chunk of a codelab step:

[[import link_to_gdoc]]

These fragment imports result in types.NodeImport. So, maybe we can call this one a types.NodeCodeImport or something like that.

[crazed]

Would love this feature as well, we've been looking at switching to this tool internally but the one feature missing is the ability to import code from a file. The syntax we currently use is from pantsbuild's markdown support, it would be nice to have some kind of support for partial imports but that may be more than you guys are looking for here.

[samtstern]

@crazed would you want support for importing files off the local filesystem or files from the network? My request was specifically about code hosted on GitHub it sounds like yours might be different?

[crazed]

For my use-case local filesystem would be preferred, but external links would also be nice for cross-repo imports.