Incrementally rebases a feature branch against a target branch commit by commit to reduce the severity and complexity of the rebase merge conflicts

git-incremental-rebase.sh

#!/bin/bash

help() {
    echo "Usage: $0 <main_branch> <feature_branch>"
    echo
    echo "Incrementally rebases a feature branch against a target branch commit by commit to reduce"
    echo "the severity and complexity of the rebase merge conflicts."
    echo
    echo "Arguments:"
    echo "  main_branch    The name of the main branch you want to rebase against."
    echo "  feature_branch The name of the feature branch you want to rebase."
    echo
    echo "Example:"
    echo "1. $0 main feature"
    echo "2. Resolve rebase conflicts"
    echo "3. git add ."
    echo "4. git rebase --continue"
    echo "5. Back to #1, until current"
}

if [ -z "$1" ] || [ -z "$2" ]; then
    help
    exit 1
fi

# Name of the main branch
main_branch=$1

# Name of the feature branch
feature_branch=$2

# Check if the working directory is clean
if ! git diff --quiet && ! git diff --cached --quiet; then
  echo "Working directory is not clean. Please commit or stash your changes before proceeding."
  exit 1
fi

# Find the common ancestor of the main and feature branches
base_commit=$(git merge-base $main_branch $feature_branch)

# Check if the base_commit exists
if ! git cat-file -e $base_commit; then
  echo "Base commit not found: $base_commit"
  exit 1
fi

echo "Found common base commit: $base_commit"
git log -n1 $base_commit

# Get the list of commit hashes in the main branch, starting from the base commit
commits=$(git log --reverse --ancestry-path --pretty=format:"%H" $base_commit..$main_branch)

# Check out the feature branch
git checkout $feature_branch

# Make a backup of the feature branch
git checkout -b ${feature_branch}-`date +%s`

# Check out the feature branch
git checkout $feature_branch

# Loop through the commits
for commit in $commits
do
    echo "Rebasing to: $commit"
    git log -n1 $commit

    # Check if the commit has more than one parent
    if [ $(git rev-list --parents -n 1 $commit | wc -w) -gt 2 ]
    then
      echo "Skipping merge commit $commit"
      continue
    fi

    # Try to rebase the feature branch onto the commit
    if ! git rebase $commit; then
        echo "Failed to rebase onto commit: $commit. Please fix the problem and run this script again."
        exit 1
    fi
done

# Print a success message
echo "Successfully rebased $feature_branch onto $main_branch"