Document the current steps for releasing CDT

[jonahgraham]

This document is to capture all the steps that I do as part of the releasing/maintenance/processing of CDT releng. As I have prepared the CDT 12.1 release I have written down every step I have taken. Once I have completed CDT 12.1 release I will merge this into the repo so this knowledge is properly captured.

[jonahgraham]

Main things left to do:

• N&N handling
• GitHub Milestones
• PMI
• Check an old endgame to make sure everything is captured properly.
• Day of release work (e.g. publishing to final URLs, updating composites)
• Coordination of CDT + CDT LSP releases

[jonahgraham]

Another new item for this document:

• If core native parts change, we need to release before Eclipse Platform because Eclipse Platform depends on us. See Add CDT core native API bundle for compilation eclipse-platform/eclipse.platform.releng.aggregator#3046 (comment)

[jld01]

Should we add creation of the new N&N page to this list? It seems useful to create it early so that we can add to it throughout the release cycle.

[ruspl-afed]

What do you think about switching p2 update site creation to JustJ technology (used by EMF, Mylyn and many others)? In my experience, this could greatly simplify the p2 delivery process.

However, I don't know how good it is for

1. service releases from branches
2. products in executable form

May be @merks can advice regarding these two use cases