Refactor `vtctld` Flags to Use Hyphen-Based Naming Convention

[mounicasruthi]

This issue is part of the ongoing flag refactor project: Flag renaming: replace underscores with dashes (#17880). Vitess is moving toward standardizing all CLI flags to use hyphen (-) instead of underscore (_) delimiters. The vtctld binary currently uses a mix of these conventions.

Plan:

• Both underscore and hyphen forms must be supported in v23 and v24
• Underscore versions will be removed in v25

This issue focuses on migrating the flags in the vtctld binary to the new format.

Note: Related PR should be based off branch flags-refactor and not main.

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Affected Binary

• vtctld

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Goal

Refactor all flags in vtctld to use dashed (-) notation instead of underscored (_), while continuing to support the old names during the deprecation period. Ensure codebase-wide consistency by updating flag usage in all references

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Scope of Work

1. Flag Refactoring

Update the registration of the flags with (_) notation in the vtctld binary

Examples:

--action_timeout 
--backup_storage_block_size 
--tablet_manager_grpc_concurrency 
--vtctld_sanitize_log_messages 

Total flags: ~76

For each, convert from:

--backup_storage_block_size

to:

--backup-storage-block-size

Use the helpers from go/vt/utils/flags.go (already available):

• SetFlagStringVar, SetFlagBoolVar, etc.
• These helpers already register both dashed and underscored variants:
  • Marks the _ form as deprecated
  • Hides the _ form from help output

Use these helpers instead of direct pflag calls.

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2. Codebase-wide Usage

Replace all underscored versions (--flag_name) with dashed versions (--flag-name) wherever they are used.

Do NOT Modify

• .diff files
• changelogs

Note: Upgrade/downgrade tests should continue using flags with underscores (--some_flag_example) to ensure backward compatibility. Add a comment in these places (if not already present) indicating that these should be replaced with dashed notation in v25.

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3. Test File Handling

If any test files set these flags programmatically, replace code like:

flags["--backup_storage_block_size"] = "4096"

with:

SetFlagVariantsForTests(flags, "--backup_storage_block_size", "4096")

Or if accessing:

GetFlagVariantForTests("--backup_storage_block_size")

This ensures both variants are tested.
If needed, create more helper functions accordingly.

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Flag Source Reference

The full list of current flags in vtctld is found here:

go/flags/endtoend/vtctld.txt

Use this to locate the exact flags that need renaming. All flags following the underscore (_) naming convention in this file should be refactored.

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Testing

Ensure tests pass in both forms by:

• Running unit and integration tests
• Verifying that test code uses SetFlagVariantsForTests or GetFlagVariantForTests or other helper functions where applicable

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📎 Related References

• Parent Issue: #17880
• Related PRs:
  • [#17975](Standardize topo flags to use hyphen-based naming #17975)
  • [#18009](Refactor grpc flags for standardized naming  #18009)
  • [#17964](Refactor vstream_dynamic_packet_size and vstream_packet_size flags to use dashes #17964
• Refactor Helpers: [go/vt/utils/flags.go](https://github.com/vitessio/vitess/blob/main/go/vt/utils/flags.go)

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