Bash script to navigate between commits in git repo

git-nav.sh

#!/bin/bash
GIT_NAV_DIR="${HOME}/.git-nav"

# Generate a file path to store commit history
# It use the MD5 hash of the Git root directory as the file name
generate_commit_file_path() {
    if git rev-parse --show-toplevel > /dev/null 2>&1; then
        git_root=$(git rev-parse --show-toplevel)
        file_name=$(echo -n "$git_root" | md5 | awk '{print $1}')
        mkdir -p ${GIT_NAV_DIR}
        echo "${GIT_NAV_DIR}/${file_name}"
        return 0
    else
        echo "Not inside a Git repository" >&2
        return 1
    fi
}

COMMITS_FILE="$(generate_commit_file_path)"
if [ $? -ne 0 ]; then
    exit 1
fi

# Function to initialize commit history
initialize_commits() {
    DEFAULT_BRANCH=$(git remote show origin | grep 'HEAD branch' | cut -d' ' -f5)
    BRANCH=$(git rev-parse --abbrev-ref HEAD)

    # check if default branch is the same as the current branch
    if [ "$DEFAULT_BRANCH" != "$BRANCH" ]; then
        MERGE_BASE=$(git merge-base "$DEFAULT_BRANCH" "$BRANCH")
        git log --reverse --pretty=format:"%H" "$MERGE_BASE..HEAD" > "$COMMITS_FILE"
    else
        git log --reverse --pretty=format:"%H" > "$COMMITS_FILE"
    fi
    
}

# Function to get the current commit index
get_current_commit_index() {
    current_commit=$(git rev-parse HEAD)
    grep -n "$current_commit" "$COMMITS_FILE" | cut -d: -f1
}

# Function to checkout the commit at a specific index
checkout_commit() {
    commit=$(sed -n "${1}p" "$COMMITS_FILE")
    if [ -n "$commit" ]; then
        git checkout "$commit"
    else
        echo "No commit found at index $1"
    fi
}

# Navigate to the next commit
next_commit() {
    current_index=$(get_current_commit_index)
    if [ -z "$current_index" ]; then
        echo "No commits found, or not on a commit."
        exit 1
    fi
    next_index=$((current_index + 1))
    checkout_commit $next_index
}

# Navigate to the previous commit
prev_commit() {
    current_index=$(get_current_commit_index)
    if [ -z "$current_index" ]; then
        echo "No commits found, or not on a commit."
        exit 1
    fi
    prev_index=$((current_index - 1))
    checkout_commit $prev_index
}

reset_commits() {
    BRANCH=$(git branch --contains HEAD | grep -v HEAD | awk '{print $1}')
    git checkout $BRANCH
}

# Handle arguments to the script
case "$1" in
    next)
        next_commit
        ;;
    prev)
        prev_commit
        ;;
    first)
        checkout_commit 1
        ;;
    reset)
        reset_commits
        ;;
    init)
        initialize_commits
        ;;
    *)
        echo "Usage: git-nav {init|next|prev|first|reset}"
        exit 1
        ;;
esac

Git Nav script

A helper script for navigating between commits in a Git branch.

While this may not be useful for everyday tasks, it can be helpful for demonstrating the progress of your feature or implementation. I use this during training sessions, where each commit contains the code implementation of the topic I want to discuss.

Usage

1. Run git-nav.sh init from the repository to initialize the script.
2. Use git-nav.sh prev to navigate to the previous commit.
3. Use git-nav.sh next to navigate to the next commit.

Alias

alias git-nav="bash <path-to-git-nav.sh>"
alias git-next="git-nav next"
alias git-prev="git-nav prev"
alias git-nav-init="git-nav init"
alias git-first="git-nav first"