Programmatic Interactive Git Rebase

This skill enables non-interactive execution of git interactive rebases. Use this when you need to:

• Absorb/fixup commits into earlier commits

• Squash multiple commits together

• Reorder commits

• Drop commits

• Reword commit messages (limited support)

The Problem

Git's interactive rebase (git rebase -i ) normally opens an editor for the user to modify a "todo" file. The GIT_SEQUENCE_EDITOR environment variable can override this, but:

• macOS BSD sed has different syntax than GNU sed for multi-line operations

• Complex todo modifications (reordering, inserting lines) are error-prone with sed

The Solution

Write the complete todo file using a temporary shell script:

1. Create a temp editor script that writes the desired todo

EDITOR_SCRIPT=$(mktemp) cat > "$EDITOR_SCRIPT" << 'SCRIPT' #!/bin/bash cat > "$1" << 'TODO' pick abc1234 First commit message fixup def5678 Commit to absorb into first pick ghi9012 Third commit stays separate TODO SCRIPT chmod +x "$EDITOR_SCRIPT"

2. Run the rebase with our custom editor

GIT_SEQUENCE_EDITOR="$EDITOR_SCRIPT" git rebase -i <base-commit>

3. Clean up

rm "$EDITOR_SCRIPT"

Step-by-Step Process

1. Identify the commits

git log --oneline -10

Note the commit hashes and messages you want to work with.

2. Determine the base commit

The base commit is the parent of the oldest commit you want to modify:

If oldest commit to modify is abc1234

git rebase -i 'abc1234^' # Note: quote the caret for zsh

3. Plan the todo list

The todo file format is:

<action> <hash> <message>

Available actions:

Action Short Description

pick

p

Use commit as-is

reword

r

Use commit but edit message (requires interaction)

edit

e

Stop for amending (requires interaction)

squash

s

Meld into previous, combine messages

fixup

f

Meld into previous, discard this message

drop

d

Remove commit entirely

4. Build and execute

EDITOR_SCRIPT=$(mktemp) cat > "$EDITOR_SCRIPT" << 'SCRIPT' #!/bin/bash cat > "$1" << 'TODO'

Your todo list here - one line per commit

pick abc1234 First commit fixup def5678 Second commit (will be absorbed) pick ghi9012 Third commit TODO SCRIPT chmod +x "$EDITOR_SCRIPT"

GIT_SEQUENCE_EDITOR="$EDITOR_SCRIPT" git rebase -i '<base>^' rm "$EDITOR_SCRIPT"

Common Operations

Absorb fix commits into a feature commit

Scenario: You have a feature commit followed by fix commits that should be part of it.

abc1234 feat: add user authentication def5678 fix: correct token validation <- absorb this ghi9012 fix: handle edge case <- and this jkl3456 chore: update deps <- keep separate

Todo:

pick abc1234 feat: add user authentication fixup def5678 fix: correct token validation fixup ghi9012 fix: handle edge case pick jkl3456 chore: update deps

Squash multiple commits with combined message

Use squash instead of fixup to keep all commit messages:

pick abc1234 feat: add user model squash def5678 feat: add user controller squash ghi9012 feat: add user routes

This will combine all three into one commit and open an editor to combine messages (or use GIT_EDITOR to automate).

Reorder commits

Simply list commits in the desired order:

pick ghi9012 Third commit (now first) pick abc1234 First commit (now second) pick def5678 Second commit (now third)

Drop a commit

Use drop or simply omit the line:

pick abc1234 Keep this drop def5678 Remove this pick ghi9012 Keep this too

Handling Conflicts

If the rebase encounters conflicts:

• The rebase will pause with a message

• Resolve conflicts in the affected files

• Stage the resolved files: git add <files>

• Continue: git rebase --continue

• Or abort: git rebase --abort

Complete Example Script

Here's a reusable function:

Programmatic interactive rebase

Usage: git_rebase_todo '<base>^' 'pick abc123 msg' 'fixup def456 msg' ...

git_rebase_todo() { local base="$1" shift

local EDITOR_SCRIPT EDITOR_SCRIPT=$(mktemp)

{ echo '#!/bin/bash' echo 'cat > "$1" << '''TODO'''' for line in "$@"; do echo "$line" done echo 'TODO' } > "$EDITOR_SCRIPT"

chmod +x "$EDITOR_SCRIPT" GIT_SEQUENCE_EDITOR="$EDITOR_SCRIPT" git rebase -i "$base" local result=$? rm "$EDITOR_SCRIPT" return $result }

Example usage:

git_rebase_todo 'abc1234^'
'pick abc1234 feat: add feature'
'fixup def5678 fix: correct issue'
'pick ghi9012 chore: update deps'

Limitations

• reword and edit actions still require user interaction for the actual editing

• Conflict resolution requires manual intervention

• Complex rebases with many commits may be easier to do interactively

Troubleshooting

"fatal: could not read file..."

The todo file path wasn't passed correctly. Ensure the script uses "$1" .

Rebase doesn't seem to do anything

Check that commit hashes in the todo match actual commits. Use short hashes (7+ chars).

zsh: no matches found: abc^

Quote the caret: 'abc1234^' or escape it: abc1234^