git_reqs_compare.py

import argparse
import git
import requirements

def get_version(req):
    """Extracts version from requirement or raises an error if not specified."""
    if req.specs:
        return req.specs[0][1]
    else:
        raise ValueError(f"Package {req.name} does not specify a version with '=='.")

def parse_requirements(file_content):
    """Parses content from a requirements.txt file and returns a dictionary of packages and their versions."""
    packages = {
        req.name: get_version(req)
        for req in requirements.parse(file_content)
    }
    return packages

def compare_requirements(before_io, after_io):
    """Compares two requirements files from IO streams and prints a list of version changes or 'no changes'."""
    before_requirements = parse_requirements(before_io)
    after_requirements = parse_requirements(after_io)

    changes = False
    for package in after_requirements:
        before_version = before_requirements.get(package, None)
        after_version = after_requirements.get(package)
        if before_version != after_version:
            changes = True
            print(f"{package} {before_version} -> {after_version}")

    if not changes:
        print("no changes")

def get_file_at_commit(repo, commit_hash, file_path):
    """Retrieves file content from a specific commit in a Git repository."""
    try:
        content = repo.commit(commit_hash).tree[file_path].data_stream.read().decode('utf-8')
    except KeyError:
        content = ""  # File does not exist at this commit
    return content

def main():
    parser = argparse.ArgumentParser(description='Compare requirements.txt file between two Git commits.')
    parser.add_argument('commit_range', nargs='?', default='HEAD', help='The commit range to compare, defaults to HEAD. Formats accepted: <commit> or <start_commit>...<end_commit>')
    parser.add_argument('file_path', nargs='?', default='requirements.txt', help='Path to the requirements.txt file within the repository, defaults to "requirements.txt"')

    args = parser.parse_args()
    repo = git.Repo()  # Assumes the script is run within a git repository

    if '...' in args.commit_range:
        commits = list(repo.iter_commits(args.commit_range))
        if not commits:
            raise ValueError("No commits found in the specified range.")
        start_commit = commits[-1] if len(commits) > 1 else commits[0].parents[0]
        end_commit = commits[0]
    else:
        commit = repo.commit(args.commit_range)
        start_commit = commit.parents[0] if commit.parents else None  # Use the parent commit if available
        end_commit = commit

    start_content = get_file_at_commit(repo, start_commit, args.file_path) if start_commit else ""
    end_content = get_file_at_commit(repo, end_commit, args.file_path)

    compare_requirements(start_content, end_content)

if __name__ == "__main__":
    main()