A CLI tool that rewrites Git history by modifying author names/emails and redistributing commits across custom date ranges.

• Author rewriting: Change author name and email for all commits
• Date redistribution: Spread commits across custom date ranges
• Time slot constraints: Restrict commits to specific hours of the day
• Minimum interval: Enforce minimum time between consecutive commits
• Multiple branches: Preserve branch structure
• Compact output: Optional quiet mode with simple commit mapping

go build -o git-time-machine ./cmd/main.go

Or download the binary:

# Clone the repository
git clone https://github.com/yourusername/git-time-machine.git
cd git-time-machine
go build -o git-time-machine ./cmd/main.go

git-time-machine [flags]

If you specify only -i (without -o), the tool shows information about the repository without rewriting:

git-time-machine -i /path/to/input/repo

This displays:

• Repository information (number of commits and unique days)
• List of all original commits with their details
• A warning that flags will be ignored since -o is missing

This mode is useful for inspecting a repository before deciding how to rewrite it. All other flags are ignored in this mode.

View repository information without rewriting:

git-time-machine -i /path/to/input/repo

This shows:

• Repository summary (commits and days)
• All original commits with their details
• Warning that flags are ignored (requires -o for rewriting)

Change the author name for all commits:

git-time-machine -i /path/to/input/repo -o /path/to/output -u "New Author"

Change both author name and email:

git-time-machine -i /path/to/input/repo -o /path/to/output \
  --user-name "John Doe" \
  --user-email "john@example.com"

Rewrite all commits to a specific date range:

git-time-machine -i /path/to/input/repo -o /path/to/output \
  --date-from 2023-01-01 \
  --date-to 2023-12-31

Restrict commits to business hours (9 AM to 5 PM):

git-time-machine -i /path/to/input/repo -o /path/to/output \
  --date-from 2023-06-01 \
  --date-to 2023-06-10 \
  --time-from 9 \
  --time-to 17

Enforce at least 2 hours between commits:

git-time-machine -i /path/to/input/repo -o /path/to/output \
  --date-from 2023-01-01 \
  --date-to 2023-01-03 \
  --min-interval 2

All features together:

git-time-machine -i /path/to/input/repo -o /path/to/output \
  --user-name "John Doe" \
  --user-email "john@example.com" \
  --date-from 2023-01-01 \
  --date-to 2023-06-30 \
  --time-from 9 \
  --time-to 18 \
  --min-interval 1

Compact output showing only the commit mapping:

git-time-machine -i /path/to/input/repo -o /path/to/output -q

• Date-only: 2006-01-02
• Date with time: 2006-01-02T15:04:05

• Hour only: 9, 10, 23 (treated as 09:00, 10:00, 23:00)
• Full time: 09:00, 14:30, 23:50

If --time-to is not specified, it defaults to 23 (23:59).

Commits are distributed across the date range using a semi-random algorithm that:

1. Spreads commits evenly across the available time
2. Respects the minimum interval constraint
3. Applies time slot constraints (if specified)
4. Ensures chronological order

By default, the tool shows:

1. Input repository summary: Number of commits and unique days
2. Original commits: Full details of each commit
3. Commit mapping: OLD_SHA --> NEW_SHA (author: old_author, date: old_date --> new_date)
4. Output repository summary: Number of commits and unique days

In quiet mode (-q), only the summary is shown.

$ git-time-machine -i /nonexistent/path -o /tmp/output
Error: failed to read repository: failed to list branches: chdir /nonexistent/path: no such file or directory

$ git-time-machine -i ./input -o ./output --date-from 2023-01-02 --date-to 2023-01-01
Error: date-from must be before date-to

$ git-time-machine -i ./input -o ./output \
  --date-from 2023-01-01 --date-to 2023-01-02 \
  --min-interval 24
Error: impossible to distribute 5 commits within 24.00 hours with minimum interval of 24 hours

$ git-time-machine -i ./input -o ./output --time-from 18 --time-to 9
Error: --time-from must be before --time-to

The tool validates that the specified constraints can accommodate all commits:

• Date range + min-interval: Ensures enough time exists for all commits with the minimum interval
• Time slot: Ensures the time slot allows valid times for all commits
• Output: Errors with clear messages when distribution is impossible

All branches from the input repository are created in the output repository. The commit SHAs change due to rewriting, but the branch structure is preserved.

• This tool rewrites Git history and should only be used on repositories that are not shared with others
• Always backup your repository before using this tool
• Changed commit SHAs affect all dependents (branch references, tags, etc.)
• The tool creates a new repository; the original remains unchanged

MIT License - See LICENSE file for details

Created by [Your Name]