Update the nightlies doc

[Gedochao]

Fixes #3206

[Gedochao]

Note: 1.0.5 is not out yet, although as per Discord discussion, it should be out soon.
Example was tested with Mill 1.0.4-53-a211b4 (it's already working on the nightly Mill version).
cc @lihaoyi

[Gedochao]

Mill 1.0.5 is freshly out, so that's solved.
https://github.com/com-lihaoyi/mill/releases/tag/1.0.5

[Gedochao]

the Longer explanation section feels redundant now, at least for the scope of this document, so I ended up removing it.
repo.scala-lang.org proxies to Scala 2 nightlies, so that part is basically an implementation detail.
Let me know if we want to preserve it somewhere.
cc @SethTisue @lrytz

[Gedochao]

Since repo.scala-lang.org proxies to Scala 2 nightlies, I ended up merging the Scala 2 and 3 sections to a large extent, and removed some stuff that no longer feels necessary.
Feel free to stop me.

[SethTisue]

I think this is now mergeable, and I suggest we merge it promptly, to make the information available now.

I have some ideas for tweaks and adjustments, but I can put that in a separate PR.

[SethTisue]

maybe the "Longer explanation" part could be internal documentation in https://github.com/scala/internal-docs instead?

[lrytz]

Looks good, thank you!

For Scala 2, the easiest way to find a specific mergely version number is to go to https://github.com/scala/scala/commits/2.13.x, find the merge commit that you want to try out, click on the "checks", scroll down to the one from travis. The version number shows up there.

Mabye that could be included?

[Gedochao]

Looks good, thank you!

For Scala 2, the easiest way to find a specific mergely version number is to go to https://github.com/scala/scala/commits/2.13.x, find the merge commit that you want to try out, click on the "checks", scroll down to the one from travis. The version number shows up there.

Mabye that could be included?

IMO that's a bit complex, while one can find it way easier at https://repo.scala-lang.org/artifactory/maven-nightlies or via Scala CLI... we can mention it in internal docs, but perhaps not in user facing ones.
@hamzaremmal's been suggesting to cut out stuff simpler than that from here already 😅

[hamzaremmal]

@hamzaremmal's been suggesting to cut out stuff simpler than that from here already 😅

Yes, suggesting to people all of these steps is just wrong. We should fine a better way. For now, I think it's okay. I will do a last review now and approve it.