Give instruction to use drone agent volumes and reduce bandwidth

[strk]

See ​https://docs.drone.io/reference/agent/drone-runner-volumes/

I *think* (but hadn't verified) that such support was added on my input to have the possibility for agents to access a directory from the host in order to reduce bandwidth. My idea was for a standard osgeo source tree on agent machines so that we could use, in .drone.yml recipes, a git option "--reference" to reference existing git repositories, which all of us developers have already. Doing so would drop the need to download over and over the source code by agents, which would have most of the code already available in the mounted volume.

BTW, I guess it would be useful to have a "Drone" component, what do you think Regina ?

[robe]

drone component? What is that?

[strk]

I meant Trac component...