BREAKING CHANGE: Add mc rb command to remove empty bucket

[poornas]

Fixes #2635 - Change mc rm --recursive behavior to
delete objects in bucket but not the
bucket itself.

[codecov]

Codecov Report

Merging #2662 into master will decrease coverage by 0.06%.
The diff coverage is 0%.

@@            Coverage Diff            @@
##           master   #2662      +/-   ##
=========================================
- Coverage    9.76%   9.69%   -0.07%     
=========================================
  Files         125     128       +3     
  Lines        9205   12106    +2901     
=========================================
+ Hits          899    1174     +275     
- Misses       8155   10782    +2627     
+ Partials      151     150       -1

Impacted Files	Coverage Δ
cmd/main.go	0% <ø> (ø)	⬆️
cmd/client-s3.go	13.27% <0%> (+0.09%)	⬆️
cmd/rm-main.go	0% <0%> (ø)	⬆️
cmd/rb-main.go	0% <0%> (ø)
cmd/mirror-main.go	0% <0%> (ø)	⬆️
cmd/client-fs.go	29.46% <0%> (+0.82%)	⬆️
cmd/session.go	35.89% <0%> (-6.48%)	⬇️
pkg/hookreader/hookreader.go	19.23% <0%> (-5.77%)	⬇️
cmd/humanized-duration.go	59.57% <0%> (-4.53%)	⬇️
pkg/probe/probe.go	42.59% <0%> (-2.24%)	⬇️
... and 115 more

---

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[harshavardhana]

We should mention this as a breaking change...

[Praveenrajmani]

I think we should not remove the bucket in the target if the source has zero contents. This should be false.

Fine if it is left intentionally to work like this.

[poornas]

@Praveenrajmani , changed it so mirror will not remove buckets

[Praveenrajmani]

Suggestion: This might be something apart from this PR (w.r.t remove log print discussions), I see the command mc rm --force minio/bucket do say that the object is being removed. But it wont actually remove without --recursive flag set. In such cases, we could perhaps fallback saying that they should use -r flag.

For ref,

[harshavardhana]

The intention here is bucket is never removed from mc mirror or mc cp operation. Even with mc rm we have decided to not remove buckets anymore.

To remove buckets explicitly only command is mc rb

[Praveenrajmani]

Tested and LGTM

[vadmeste]

@poornas after introducing rb command, do you expect that rm is still able to remove objects from different buckets at the same time ?

[poornas]

@poornas after introducing rb command, do you expect that rm is still able to remove objects from different buckets at the same time ?

@vadmeste, yes - both the commands below will remove objects from different buckets, except that mc rb will delete bucket in addition.

➜  mc git:(rb) mc rb --force s3/tbucket11 s3/tbucket13
Bucket removed successfully `s3/tbucket11`.
Bucket removed successfully `s3/tbucket13`.

and

➜  mc git:(rb) mc rm --r --force s3/tbucket11 s3/tbucket13

[vadmeste]

@poornas I see, but I also mean this:
mc rm alias/

does it also need to traverse several buckets and remove all objects in them ?

[poornas]

@poornas I see, but I also mean this:
mc rm alias/

does it also need to traverse several buckets and remove all objects in them ?
@vadmeste , that functionality also remains the same as before.

[vadmeste]

LGTM except some minor changes

[vadmeste]

LGTM