Feat/enhance drop warning

[kazuooooo]

Summary

• Add --confirm-drops option to control drop warning behavior
• Default: shows simple warning message for drop statements
• With --confirm-drops: displays detailed warning and requires user confirmation
• Helps prevent accidental data loss from column renames being detected as DROP+ADD operations

Motivation

Currently, supabase db diff shows a very weak warning when DROP statements are detected.

Found drop statements in schema diff. Please double check if these are expected:
alter table "public"."map_groups" drop column "import_status"
alter table "public"."map_groups" drop column "memo" 

This is particularly problematic for column renames, which are detected as DROP COLUMN + ADD COLUMN operations, potentially causing data loss. #1721 (comment)
(I actually encountered this issue and it caused a major system failure. I am creating this Pull Request to prevent further victims.)

Changes

• Add --confirm-drops boolean flag to db diff command
• Default behavior (no flag): Shows simple warning message for detected DROP statements
• With --confirm-drops flag: Shows detailed danger warning with:
  • Red highlighting and visual separator
  • List of all detected DROP statements with red arrows
  • Explanation of specific risks including column renames and data loss
  • Interactive confirmation prompt with default "No" for safety
  • Operation cancelled if user declines
• Applies to both migra and pgadmin diff modes

Test plan

• Added unit tests for the option handling
• Manual testing with actual DROP operations
• Manual testing with column rename scenarios

Example usage

Default behavior (simple warning)

supabase db diff

Output:

Found drop statements in schema diff. Please double check if these are expected:
ALTER TABLE public.users DROP COLUMN old_name
DROP TABLE public.legacy_data

With confirmation prompt

supabase db diff --confirm-drops

Output:

⚠️  DANGEROUS OPERATION DETECTED
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

The following DROP statements were found in your schema diff:

  ▶ ALTER TABLE public.users DROP COLUMN old_name
  ▶ DROP TABLE public.legacy_data

❗ These operations may cause DATA LOSS:
  • Column renames are detected as DROP + ADD, which will lose existing data
  • Table or schema deletions will permanently remove all data
  • Consider using RENAME operations instead of DROP + ADD for columns

Please review the generated migration file carefully before proceeding.

Do you want to continue with this potentially destructive operation? [y/N]

🤖 Generated with Claude Code