Quick script to compare a given branch (default main) towards the last tag in order to identify the new changes

compare-release.sh

#!/bin/bash

# compare-release.sh - Compare git tags with branches
# Usage: 
#   ./compare-release.sh                    # Compare last tag with main
#   ./compare-release.sh --branch develop   # Compare with specific branch
#   ./compare-release.sh --detailed         # Show detailed diff
#   ./compare-release.sh --commits-only     # Show only commits

set -e

# Default values
BRANCH="main"
SHOW_DETAILED=false
COMMITS_ONLY=false

# Colors
RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[1;33m'
BLUE='\033[0;34m'
NC='\033[0m'

# Disable git pager for this script
export GIT_PAGER=cat

# Parse arguments
while [[ $# -gt 0 ]]; do
    case $1 in
        --branch)
            BRANCH="$2"
            shift 2
            ;;
        --detailed)
            SHOW_DETAILED=true
            shift
            ;;
        --commits-only)
            COMMITS_ONLY=true
            shift
            ;;
        --help)
            echo "Usage: $0 [OPTIONS]"
            echo "Options:"
            echo "  --branch <name>    Compare with specific branch (default: main)"
            echo "  --detailed         Show detailed file diffs"
            echo "  --commits-only     Show only commit messages"
            echo "  --help             Show this help message"
            exit 0
            ;;
        *)
            echo "Unknown option: $1"
            exit 1
            ;;
    esac
done

echo -e "${BLUE}=== Comparing Last Release Tag with ${BRANCH} ===${NC}\n"

# Fetch latest
echo -e "${YELLOW}Fetching latest from remote...${NC}"
git fetch --tags --quiet
git fetch origin ${BRANCH} --quiet

# Get the last tag
LAST_TAG=$(git describe --tags --abbrev=0 2>/dev/null || echo "")

if [ -z "$LAST_TAG" ]; then
    echo -e "${RED}No tags found in repository${NC}"
    exit 1
fi

echo -e "${GREEN}Last released tag: ${LAST_TAG}${NC}"
echo -e "${GREEN}Comparing with: origin/${BRANCH}${NC}\n"

# Count commits
COMMIT_COUNT=$(git rev-list ${LAST_TAG}..origin/${BRANCH} --count)

if [ "$COMMIT_COUNT" -eq 0 ]; then
    echo -e "${GREEN}✓ No new commits since last release${NC}"
    exit 0
fi

echo -e "${YELLOW}Found ${COMMIT_COUNT} new commits${NC}\n"

# Show commits (--no-pager ensures output is not paginated)
echo -e "${BLUE}=== Commit History ===${NC}"
git --no-pager log ${LAST_TAG}..origin/${BRANCH} \
    --pretty=format:"%C(yellow)%h%C(reset) - %C(green)(%ar)%C(reset) %s %C(blue)- %an%C(reset)" \
    --abbrev-commit

if [ "$COMMITS_ONLY" = true ]; then
    exit 0
fi

# File statistics
echo -e "\n\n${BLUE}=== Files Changed ===${NC}"
git --no-pager diff ${LAST_TAG}..origin/${BRANCH} --stat

echo -e "\n${BLUE}=== Changed Files List ===${NC}"
git --no-pager diff ${LAST_TAG}..origin/${BRANCH} --name-status | while read status file; do
    case $status in
        A) echo -e "${GREEN}[ADDED]${NC}    $file" ;;
        M) echo -e "${YELLOW}[MODIFIED]${NC} $file" ;;
        D) echo -e "${RED}[DELETED]${NC}  $file" ;;
        R*) echo -e "${BLUE}[RENAMED]${NC}  $file" ;;
        *) echo -e "[${status}] $file" ;;
    esac
done

# Detailed diff if requested
if [ "$SHOW_DETAILED" = true ]; then
    echo -e "\n${BLUE}=== Detailed Diff ===${NC}"
    git --no-pager diff ${LAST_TAG}..origin/${BRANCH}
fi

# Summary
echo -e "\n${BLUE}=== Release Summary ===${NC}"
echo -e "Previous version: ${GREEN}${LAST_TAG}${NC}"
echo -e "Target branch:    ${GREEN}origin/${BRANCH}${NC}"
echo -e "Total commits:    ${GREEN}${COMMIT_COUNT}${NC}"
echo -e "Files changed:    ${GREEN}$(git --no-pager diff ${LAST_TAG}..origin/${BRANCH} --name-only | wc -l | tr -d ' ')${NC}"

STATS=$(git --no-pager diff ${LAST_TAG}..origin/${BRANCH} --shortstat)
INSERTIONS=$(echo "$STATS" | grep -oE '[0-9]+ insertion' | grep -oE '[0-9]+' || echo 0)
DELETIONS=$(echo "$STATS" | grep -oE '[0-9]+ deletion' | grep -oE '[0-9]+' || echo 0)

echo -e "Lines added:      ${GREEN}+${INSERTIONS}${NC}"
echo -e "Lines removed:    ${RED}-${DELETIONS}${NC}"

echo -e "\n${BLUE}=== Authors Contributing ===${NC}"
git --no-pager shortlog ${LAST_TAG}..origin/${BRANCH} -sn