VReplication: Add --shards flag to MoveTables/Reshard start and stop commands

[varundeepsaini]

Description

Adds support for the --shards flag to the start and stop commands for MoveTables and Reshard VReplication workflows. This allows users to start or stop workflows on a specific subset of shards rather than all shards at once.

Related Issue(s)

Fixes: #18949

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
• If this change is to be back-ported to previous releases, a justification is included in the PR description
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

Deployment Notes

No deployment notes. This is a CLI enhancement with no database migrations or breaking changes.

AI Disclosure

This PR was authored with assistance from Claude.

[vitess-bot]

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[promptless]

📝 Documentation updates detected!

New suggestion: Add --shards flag to MoveTables and Reshard start/stop commands

[promptless]

📝 Documentation updates detected!

New suggestion: Add changelog entry for VReplication --shards flag

[mattlord]

Thanks, @varundeepsaini !

There's more work to be done on the client side -- as we're not passing the shards in the request:

vitess/go/cmd/vtctldclient/command/vreplication/common/update.go

Lines 139 to 148 in 802b55e

	// The only thing we're updating is the state.
	req := &vtctldatapb.WorkflowUpdateRequest{
	Keyspace: workflowOptions.Keyspace,
	TabletRequest: &tabletmanagerdatapb.UpdateVReplicationWorkflowRequest{
	Workflow: workflowUpdateOptions.Workflow,
	Cells: textutil.SimulatedNullStringSlice,
	TabletTypes: textutil.SimulatedNullTabletTypeSlice,
	State: &state,
	},
	}

It's a different call path for workflow stop/start:

vitess/go/cmd/vtctldclient/command/vreplication/workflow/state.go

Lines 78 to 88 in 802b55e

	// The only thing we're updating is the state.
	req := &vtctldatapb.WorkflowUpdateRequest{
	Keyspace: baseOptions.Keyspace,
	TabletRequest: &tabletmanagerdatapb.UpdateVReplicationWorkflowRequest{
	Workflow: baseOptions.Workflow,
	Cells: textutil.SimulatedNullStringSlice,
	TabletTypes: textutil.SimulatedNullTabletTypeSlice,
	State: &state,
	Shards: shards,
	},
	}

We should also add some test coverage for this.

[varundeepsaini]

hey @mattlord ,
will add the tests
However, I didnt exactly get the more work part. Could you please be more specific?

[mattlord]

@varundeepsaini I literally cannot be more specific. :-) The issue will auto-close w/o any progress in the coming weeks.

[varundeepsaini]

hey @mattlord
i have added the tests, could you review and re run the failed tests (they aren't related to my changes)

[codecov]

Codecov Report

❌ Patch coverage is 92.30769% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 69.91%. Comparing base (d38ee62) to head (986504d).
⚠️ Report is 9 commits behind head on main.

Files with missing lines	Patch %	Lines
...vtctldclient/command/vreplication/common/update.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #19023      +/-   ##
==========================================
+ Coverage   69.90%   69.91%   +0.01%     
==========================================
  Files        1613     1613              
  Lines      216076   216085       +9     
==========================================
+ Hits       151055   151085      +30     
+ Misses      65021    65000      -21     

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[mattlord]

Nice work @varundeepsaini ! Thank you ❤️

[mhamza15]

Nice!

[promptless]

📝 Documentation updates detected!

New suggestion: Add --shards flag to MoveTables and Reshard start/stop command docs