Validate Git Safety Skill

Purpose: Validate git history-rewriting operations won't affect protected branches or cause unintended data loss.

When to Use

• Before git filter-branch
• Before git rebase with --all or --branches
• Before any history-rewriting operation
• Before deleting branches

Protected Branch Patterns

Version Branches (NEVER modify)

• Pattern: v[0-9]+ (e.g., v1, v13, v21)
• Protection: NEVER delete, rewrite history, or force push

Main/Master (careful modifications only)

• Only fast-forward merges
• No history rewriting

Task Branches

• Treat as immutable after completion

Dangerous Commands

# NEVER use --all with history rewriting
git filter-branch --all
git rebase --all

# NEVER force push without explicit request
git push --force
git push -f

# NEVER delete version branches
git branch -D v21

# NEVER rebase shared branches
git checkout main
git rebase feature  # Rewrites main!

Safe Alternatives

# Target specific branch (not --all)
git filter-branch main

# Rebase feature onto main (not main onto feature)
git checkout feature
git rebase main

# Use --force-with-lease instead of --force
git push --force-with-lease

# Move version branch pointer forward (not rewrite)
git branch -f v21 <new-commit>

Pre-Operation Checklist

Before any history-rewriting operation:

1. List all branches: git branch -a
2. Identify protected branches: git branch | grep -E "^ v[0-9]+"
3. Verify command targets specific branch (not --all)
4. Create backup: git branch backup-before-op-$(date +%Y%m%d-%H%M%S)
5. Execute operation
6. Verify protected branches unchanged
7. Cleanup backup

Validation Before Dangerous Operations

# Before running dangerous command, check:
COMMAND="git filter-branch --tree-filter 'rm secrets.txt' HEAD"

# Check for dangerous flags
if echo "$COMMAND" | grep -qE "(--all|--branches)"; then
  echo "BLOCKED: --all/--branches affects protected branches"
  echo "Use: git filter-branch <branch-name>"
  exit 1
fi

# Check target isn't version branch
TARGET=$(echo "$COMMAND" | grep -oE "v[0-9]+")
if [[ -n "$TARGET" ]]; then
  echo "BLOCKED: Cannot modify version branch $TARGET"
  exit 1
fi

echo "Command appears safe"

Recovery If Protected Branch Modified

# If version branch history was modified:

# 1. Check reflog for original position
git reflog show v21

# 2. Reset to original commit
git branch -f v21 v21@{1}

# 3. Verify restored
git log v21 -5 --oneline

Success Criteria

• Identified all protected branches
• Command doesn't use --all or --branches
• Command doesn't target version branches
• Backup created before operation
• Protected branches unchanged after operation