Implement 'rewrite' command to exclude files from existing snapshots

[depau]

What does this PR change? What problem does it solve?

Since the changes in #2731 haven't seen any progress in the last two years, I thought I'd pick up from where the original author left off and apply the suggested changes.

The current changes include:

• Rebase on top of master + fix API usage
• Apply the trivial review suggestions

This is still WIP.

From the original PR:

This adds 'rewrite' command that provides a way to remove data from existing snapshots.

This is some sort of preliminary pull requests. It's actually works here on test repo, but lacks tests, etc. Mostly to discuss things

Was the change previously discussed in an issue or on the forum?

closes #14
closes #2731

Checklist

• I have read the contribution guidelines.
• I have enabled maintainer edits.
• I have added tests for all code changes.
• I have added documentation for relevant changes (in the manual).
• There's a new file in changelog/unreleased/ that describes the changes for our users (see template).
• I have run gofmt on the code in all commits.
• All commit messages are formatted in the same style as the other commits in the repo.
  • I'm planning to try stuff for the time being, I will rebase appropriately when ready
• I'm done! This pull request is ready for review.

[DRON-666]

@depau perhaps you'd be interested in this fork. I implemented all @aawsome suggestions and added some flags like --exclude-larger-than and --iexclude-file.
I think other flags like --set-path, --set-time, --set-host should be added as well.

[ibash]

Thank you, using this right now!

[ibash]

nitpick: IMO it'd be better to make this Verbosef so that the user can see it.

[depau]

@depau perhaps you'd be interested in this fork. I implemented all @aawsome suggestions and added some flags like --exclude-larger-than and --iexclude-file. I think other flags like --set-path, --set-time, --set-host should be added as well.

Sounds good! You should probably open your own pull request then, I'll close this one.

[danielsharvey]

@DRON-666 Will you create a PR for your changes?

[DRON-666]

@danielsharvey I don't think another (third or fourth?) half-baked PR is a good idea.

[dionorgua]

I don't have time right now to work on this. So if anybody want to take care of this pull request, feel free to do this