Refactor backup progress

[amozoss]

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

ui/backup.go and ui/json/backup.go are almost identical to one another (copy paste).

This change refactors the shared logic into progress.go.

ui/backup.go and ui/json/backup.go have already begun to diverge, for example

// for the last item "/", current is nil
if current != nil { 
   p.summary.ProcessedBytes += current.Size
}

p.summary.ProcessedBytes += current.Size was done outside of the lock in json/backup.go , but ui/backup.go had the above

This will continue to be a "hope we don't forget to update the other place" problem..

This change also allows the progress reporting/printing to be shared with restore status (forth coming after this is merged).

Was the change discussed in an issue or in the forum before?

No it wasn't

Checklist

• I have read the Contribution Guidelines
• I have enabled maintainer edits for this PR
• I have added tests for all changes in this PR
• I have added documentation for the changes (in the manual)
• There's a new file in changelog/unreleased/ that describes the changes for our users (template here)
• 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 done, this Pull Request is ready for review

[greatroar]

I don't agree with omitting "archive" or "backup" from the names of the moved types, which are all specific to the backup command. The generic names ui.Counter and ui.Progress mentally conflict with ui/progress.Counter. If this must be moved out of cmd/restic, I suggest it be moved to a new package, maybe archiver/ui, ui/archiver or ui/backup.

[amozoss]

Thanks for you comment, I'm not sure I follow what you're saying. I renamed the interface so that I could re-use the logic of the progress reporting with restores (I haven't submitted that change yet, it depends on this refactor).

[MichaelEischer]

@amozoss
I've rebased the commit onto the current master. The main change during the rebase is that there's now a SetDryRun() method.

Besides that I've made a few other noteworthy changes:

• The JSON statistics part of the summary output is restored, which was lost during the refactoring.
• I've removed the unused TotalErrors field from the Summary struct.
• backup --json | cat - no longer printed status updates. I've fixed that regression. Now only backup --json --quiet disabled the status updates. The latter actually is a change compared to the current behavior where backup --json --quiet and backup --json behave similarly.

The Counter struct had also diverged between the text and JSON output.

Regarding the name of the Counter and the Summary struct I agree with greatroar that these are pretty generic and could be confusing. The cleanest way would probably to move everything, that is the backup.go files and progress.go, into a package internal/ui/backup. However, as you've mentioned that you want to reuse some part of the logic for restore, I'm wondering whether some other structure would be preferable.

[MichaelEischer]

I've added a changelog that his PR also fixes #2738.

@greatroar The backup ui code is for now consolidated in ui/backup.

[MichaelEischer]

LGTM.