Implement retention policy

[sebastienros]

Delete packages based on:

• older than last n pre-release versions
• older than last n release versions

Not by date. Just in order to keep a limited set of packages.

[emgarten]

I like the version based approach to limit packages, this would be easy to use and straight forward to implement in Sleet.

It could work by:

• Store the release/pre-release limit values on the feed in settings. This can be set with the feed-settings command for any value, or a new command could be added to make surface this.
• After a push operation check for packages over the limit by using sleet.packageindex.json
• Apply deletes
• Commit all feed changes

[LordMike]

Possibly add a retention-clean command that has a --no-op / --dry-run option.

Concerns / use cases (focusing on SemVer - ie. 3 components + prerelease tag):

• Keep last N pre-release versions, counted for each Major.Minor.Patch version (1.0.1-alpha1 and 1.0.2-alpha1 count as 1 pre-release for versions 1 and 2 ..)
  • Alternate: Keep last N pre-release versions, counted globally
  • Alternate: Keep last N pre-release versions ..
  • For the last A major versions
  • For their last B minor versions
  • For their last C patch versions
• Keep last N major/minor/patch versions (Major.Minor.Patch)
  • Alternate: Keep all released versions (ie. disable retention policies for released)

I could envision a situation where I'd also want different rules. An example is a speedy development cycle, where we might want to keep ALL pre-releases for the CURRENT/LATEST version, but a limited set of the non-latest versions.. And then finally, for the previous major version, we might keep no pre-releases at all.

I don't know yet how to describe this in rules.

[emgarten]

Package retention has been added in https://www.nuget.org/packages/Sleet/3.1.8

@LordMike I'm going to start with the basic scenarios for package retention. I've included --dry-run per your suggestion, I think that is a great idea. For more complex pruning scenario I'm interested in how these could be described or if an extension point is needed for this.