Git Rewrite History

Git Rewrite History

Safely rewrite git history with mandatory dry-run planning and user confirmation.

Critical Rules

1. ALWAYS DRY RUN FIRST - Propose plan, never execute without approval
2. ALWAYS WAIT FOR CONFIRMATION - User must explicitly approve before destructive operations
3. ALWAYS CREATE BACKUP - Backup branch before any rebase/​amend
4. ALWAYS SAVE TAG MESSAGES - Preserve tag annotations before deletion

Supported Operations

Workflow

Phase 1: ANALYZE

Gather current state before proposing changes.

# Current branch and HEAD
git rev-parse --abbrev-ref HEAD
git rev-parse --short HEAD

# Commit history
git log --oneline --decorate main

# All tags
git tag -l

# All branches
git branch -a -v

Phase 2: PLAN (DRY RUN)

OUTPUT FORMAT:

## DRY RUN - PROPOSED PLAN

### Current State
- Branch: {branch}
- HEAD: {sha}
- Commits: {count}
- Tags: {list}

### Operations
1. {operation description}
2. {operation description}
...

### Commands to Execute
{numbered list of exact commands}

### Risk Assessment
| Risk | Impact | Mitigation |
|------|--------|------------|

### Affected
- Commits: {list}
- Tags: {list}
- Remote: {yes/​no force push required}

**Awaiting approval to proceed.**

Phase 3: CONFIRM

STOP AND WAIT for user to respond with approval (e.g., "OK", "proceed", "yes").

Phase 4: BACKUP

# Create backup branch
git branch backup/​pre-rewrite-$(date +%Y%m%d-%H%M%S) HEAD

# Save tag messages to temp files
git tag -l --format='%(contents)' {tag} > /​tmp/​{tag}-message.txt

Phase 5: EXECUTE

Pattern A: Amend Content in Historical Commit

# Save cleaned file
cp {file} /​tmp/​cleaned-file

# Stash if needed
git stash

# Start interactive rebase (mark target as "edit")
GIT_SEQUENCE_EDITOR="sed -i '' 's/^pick {short_sha}/​edit {short_sha}/'" git rebase -i {parent_sha}

# Apply changes when stopped
cp /​tmp/​cleaned-file {file}
git add {file}
git commit --amend --no-edit

# Continue
git rebase --continue

Pattern B: Squash N Commits into 1

# For commits 2-N, change "pick" to "squash"
GIT_SEQUENCE_EDITOR="sed -i '' '2,{N}s/^pick/​squash/'" git rebase -i --root
# OR for non-root:
GIT_SEQUENCE_EDITOR="sed -i '' '2,{N}s/^pick/​squash/'" git rebase -i {parent_sha}

# When prompted for message, use edit mode:
GIT_SEQUENCE_EDITOR="sed -i '' '1s/^pick/​edit/'" git rebase -i --root
git commit --amend -m "{new_message}"
git rebase --continue

Pattern C: Reword Commit Message

# Mark commit for edit
GIT_SEQUENCE_EDITOR="sed -i '' 's/^pick {short_sha}/​edit {short_sha}/'" git rebase -i {parent_sha}

# Amend message
git commit --amend -m "{new_message}"

# Continue
git rebase --continue

Pattern D: Delete Branches

# Local branches
git branch -D {branch1} {branch2}

# Remote branches
git push origin --delete {branch1} {branch2}

Phase 6: UPDATE TAGS

After any rebase, commit hashes change. Tags must be recreated.

# Get new commit hashes
git log --oneline -{N} main

# Delete old tags (local)
git tag -d {tag1} {tag2}

# Recreate tags on new commits
git tag -a {tag} {new_sha} -F /​tmp/​{tag}-message.txt
# OR with inline message:
git tag -a {tag} {new_sha} -m "{message}"

Phase 7: FORCE PUSH

# Delete remote tags first
git push origin :refs/​tags/​{tag1} :refs/​tags/​{tag2}

# Force push branch
git push --force-with-lease origin {branch}

# Push new tags
git push origin {tag1} {tag2}

Phase 8: VERIFY

# Final history
git log --oneline --decorate -{N} main

# Commit count
git rev-list --count main

# Tags
git tag -l | sort -V

# Remote sync
git status

Output Format

After completion, report:

## Complete

### Final State
{commit} (tag: {tag}) {message}
{commit} (tag: {tag}) {message}
...

### Summary
| Metric | Before | After |
|--------|--------|-------|
| Commits | {N} | {M} |
| Tags | {list} | {list} |

### Verification
| Check | Result |
|-------|--------|
| Commit count | {N} |
| Tags exist | {list} |
| Remote synced | Yes/​No |

Safety Notes

• --force-with-lease prevents overwriting others' work
• Backup branches preserve original state for rollback
• Tag messages saved to /​tmp allow recreation with original annotations
• Reflog preserves history locally (expires after 90 days by default)