Increase the granularity of the "keep within" snapshot retention policy

[plumbeo]

What is the purpose of this change? What does it change?

Increase the minimum granularity of the time ranges accepted by the restic forget --keep-within command from a daily granularity to an hourly granularity.

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

Yes, in issue #2089.

Checklist

• I have read the Contribution Guidelines
• 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

[plumbeo]

I didn't add new tests covering the change to snapshot_policy_test.go yet because I'm not sure about how to generate the testdata.

[codecov-io]

Codecov Report

Merging #2090 into master will decrease coverage by 4.13%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #2090      +/-   ##
==========================================
- Coverage   50.78%   46.65%   -4.14%     
==========================================
  Files         176      176              
  Lines       14165    14169       +4     
==========================================
- Hits         7194     6610     -584     
- Misses       5920     6565     +645     
+ Partials     1051      994      -57

Impacted Files	Coverage Δ
internal/restic/duration.go	76.47% <100%> (+1.47%)	⬆️
cmd/restic/cmd_forget.go	42.85% <100%> (ø)	⬆️
internal/restic/snapshot_policy.go	74.33% <100%> (ø)	⬆️
internal/backend/b2/b2.go	0% <0%> (-80.69%)	⬇️
internal/backend/swift/swift.go	0% <0%> (-78.45%)	⬇️
internal/backend/gs/gs.go	0% <0%> (-73.61%)	⬇️
internal/backend/azure/azure.go	0% <0%> (-69.46%)	⬇️
internal/backend/swift/config.go	36.95% <0%> (-54.35%)	⬇️
internal/checker/checker.go	64.54% <0%> (-3.87%)	⬇️
internal/backend/rclone/backend.go	66.08% <0%> (+1.75%)	⬆️
... and 2 more

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[fd0]

Nice idea, I like it! Add the tests to snapshot_policy_test.go, then run the tests with go test -v -update -run TestApplyPolicy, then inspect the new (updated) files in testdata/. If they look good (the results are correct), commit the files. This technique uses so-called "golden" files to compare the result of an operation with the expected result without manually having to write the long and complicated files.

[fd0]

Add the tests, then I think this change is good to be merged. Thanks!

[plumbeo]

@fd0 I just pushed a modified commit that also add tests. Also, in the option description wasn't "older" supposed to be "newer"?

[fd0]

Also, in the option description wasn't "older" supposed to be "newer"?

Huh, I think you're right!

[fd0]

LGTM, thanks!