path: root/buildscripts/clang_format.py

#!/usr/bin/env python
"""
A script that provides:
1. Ability to grab binaries where possible from LLVM.
2. Ability to download binaries from MongoDB cache for clang-format.
3. Validates clang-format is the right version.
4. Has support for checking which files are to be checked.
5. Supports validating and updating a set of files to the right coding style.
"""
from __future__ import print_function, absolute_import

import Queue
import difflib
import glob
import itertools
import os
import re
import shutil
import string
import subprocess
import sys
import tarfile
import tempfile
import threading
import time
import urllib2
from distutils import spawn
from optparse import OptionParser
from multiprocessing import cpu_count

# Get relative imports to work when the package is not installed on the PYTHONPATH.
if __name__ == "__main__" and __package__ is None:
    sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(os.path.realpath(__file__)))))

from buildscripts import moduleconfig


##############################################################################
#
# Constants for clang-format
#
#

# Expected version of clang-format
CLANG_FORMAT_VERSION = "3.8.0"
CLANG_FORMAT_SHORT_VERSION = "3.8"

# Name of clang-format as a binary
CLANG_FORMAT_PROGNAME = "clang-format"

# URL location of the "cached" copy of clang-format to download
# for users which do not have clang-format installed
CLANG_FORMAT_HTTP_LINUX_CACHE = "https://s3.amazonaws.com/boxes.10gen.com/build/clang-format-3.8-rhel55.tar.gz"

CLANG_FORMAT_HTTP_DARWIN_CACHE = "https://s3.amazonaws.com/boxes.10gen.com/build/clang%2Bllvm-3.8.0-x86_64-apple-darwin.tar.xz"

# Path in the tarball to the clang-format binary
CLANG_FORMAT_SOURCE_TAR_BASE = string.Template("clang+llvm-$version-$tar_path/bin/" + CLANG_FORMAT_PROGNAME)

# Path to the modules in the mongodb source tree
# Has to match the string in SConstruct
MODULE_DIR = "src/mongo/db/modules"

##############################################################################

# Copied from python 2.7 version of subprocess.py
# Exception classes used by this module.
class CalledProcessError(Exception):
    """This exception is raised when a process run by check_call() or
    check_output() returns a non-zero exit status.
    The exit status will be stored in the returncode attribute;
    check_output() will also store the output in the output attribute.
    """
    def __init__(self, returncode, cmd, output=None):
        self.returncode = returncode
        self.cmd = cmd
        self.output = output
    def __str__(self):
        return ("Command '%s' returned non-zero exit status %d with output %s" %
            (self.cmd, self.returncode, self.output))


# Copied from python 2.7 version of subprocess.py
def check_output(*popenargs, **kwargs):
    r"""Run command with arguments and return its output as a byte string.

    If the exit code was non-zero it raises a CalledProcessError.  The
    CalledProcessError object will have the return code in the returncode
    attribute and output in the output attribute.

    The arguments are the same as for the Popen constructor.  Example:

    >>> check_output(["ls", "-l", "/dev/null"])
    'crw-rw-rw- 1 root root 1, 3 Oct 18  2007 /dev/null\n'

    The stdout argument is not allowed as it is used internally.
    To capture standard error in the result, use stderr=STDOUT.

    >>> check_output(["/bin/sh", "-c",
    ...               "ls -l non_existent_file ; exit 0"],
    ...              stderr=STDOUT)
    'ls: non_existent_file: No such file or directory\n'
    """
    if 'stdout' in kwargs:
        raise ValueError('stdout argument not allowed, it will be overridden.')
    process = subprocess.Popen(stdout=subprocess.PIPE, *popenargs, **kwargs)
    output, unused_err = process.communicate()
    retcode = process.poll()
    if retcode:
        cmd = kwargs.get("args")
        if cmd is None:
            cmd = popenargs[0]
        raise CalledProcessError(retcode, cmd, output)
    return output

def callo(args):
    """Call a program, and capture its output
    """
    return check_output(args)

def get_tar_path(version, tar_path):
    """ Get the path to clang-format in the llvm tarball
    """
    return CLANG_FORMAT_SOURCE_TAR_BASE.substitute(
        version=version,
        tar_path=tar_path)

def extract_clang_format(tar_path):
    # Extract just the clang-format binary
    # On OSX, we shell out to tar because tarfile doesn't support xz compression
    if sys.platform == 'darwin':
         subprocess.call(['tar', '-xzf', tar_path, '*clang-format*'])
    # Otherwise we use tarfile because some versions of tar don't support wildcards without
    # a special flag
    else:
        tarfp = tarfile.open(tar_path)
        for name in tarfp.getnames():
            if name.endswith('clang-format'):
                tarfp.extract(name)
        tarfp.close()

def get_clang_format_from_cache_and_extract(url, tarball_ext):
    """Get clang-format from mongodb's cache
    and extract the tarball
    """
    dest_dir = tempfile.gettempdir()
    temp_tar_file = os.path.join(dest_dir, "temp.tar" + tarball_ext)

    # Download from file
    print("Downloading clang-format %s from %s, saving to %s" % (CLANG_FORMAT_VERSION,
            url, temp_tar_file))

    # Retry download up to 5 times.
    num_tries = 5
    for attempt in range(num_tries):
        try:
            resp = urllib2.urlopen(url)
            with open(temp_tar_file, 'wb') as f:
              f.write(resp.read())
            break
        except urllib2.URLError:
            if attempt == num_tries - 1:
                raise
            continue

    extract_clang_format(temp_tar_file)

def get_clang_format_from_darwin_cache(dest_file):
    """Download clang-format from llvm.org, unpack the tarball,
    and put clang-format in the specified place
    """
    get_clang_format_from_cache_and_extract(CLANG_FORMAT_HTTP_DARWIN_CACHE, ".xz")

    # Destination Path
    shutil.move(get_tar_path(CLANG_FORMAT_VERSION, "x86_64-apple-darwin"), dest_file)

def get_clang_format_from_linux_cache(dest_file):
    """Get clang-format from mongodb's cache
    """
    get_clang_format_from_cache_and_extract(CLANG_FORMAT_HTTP_LINUX_CACHE, ".gz")

    # Destination Path
    shutil.move("build/bin/clang-format", dest_file)

class ClangFormat(object):
    """Class encapsulates finding a suitable copy of clang-format,
    and linting/formating an individual file
    """
    def __init__(self, path, cache_dir):
        self.path = None
        clang_format_progname_ext = ""

        if sys.platform == "win32":
            clang_format_progname_ext += ".exe"

        # Check the clang-format the user specified
        if path is not None:
            if os.path.isfile(path):
                self.path = path
            else:
                print("WARNING: Could not find clang-format %s" % (path))

        # Check the environment variable
        if "MONGO_CLANG_FORMAT" in os.environ:
            self.path = os.environ["MONGO_CLANG_FORMAT"]

            if self.path and not self._validate_version():
                self.path = None

        # Check the users' PATH environment variable now
        if self.path is None:
            # Check for various versions staring with binaries with version specific suffixes in the
            # user's path
            programs = [
                    CLANG_FORMAT_PROGNAME + "-" + CLANG_FORMAT_VERSION,
                    CLANG_FORMAT_PROGNAME + "-" + CLANG_FORMAT_SHORT_VERSION,
                    CLANG_FORMAT_PROGNAME,
                    ]

            if sys.platform == "win32":
                for i in range(len(programs)):
                    programs[i] += '.exe'

            for program in programs:
                self.path = spawn.find_executable(program)

                if self.path:
                    if not self._validate_version():
                        self.path = None
                    else:
                        break

        # If Windows, try to grab it from Program Files
        # Check both native Program Files and WOW64 version
        if sys.platform == "win32":
            programfiles = [
                os.environ["ProgramFiles"],
                os.environ["ProgramFiles(x86)"],
                ]

            for programfile in programfiles:
                win32bin = os.path.join(programfile, "LLVM\\bin\\clang-format.exe")
                if os.path.exists(win32bin):
                    self.path = win32bin
                    break

        # Have not found it yet, download it from the web
        if self.path is None:
            if not os.path.isdir(cache_dir):
                os.makedirs(cache_dir)

            self.path = os.path.join(cache_dir, CLANG_FORMAT_PROGNAME + "-" + CLANG_FORMAT_VERSION + clang_format_progname_ext)

            # Download a new version if the cache is empty or stale
            if not os.path.isfile(self.path) or not self._validate_version():
                if sys.platform.startswith("linux"):
                    get_clang_format_from_linux_cache(self.path)
                elif sys.platform == "darwin":
                    get_clang_format_from_darwin_cache(self.path)
                else:
                    print("ERROR: clang-format.py does not support downloading clang-format " +
                        " on this platform, please install clang-format " + CLANG_FORMAT_VERSION)

        # Validate we have the correct version
        # We only can fail here if the user specified a clang-format binary and it is the wrong
        # version
        if not self._validate_version():
            print("ERROR: exiting because of previous warning.")
            sys.exit(1)

        self.print_lock = threading.Lock()

    def _validate_version(self):
        """Validate clang-format is the expected version
        """
        cf_version = callo([self.path, "--version"])

        if CLANG_FORMAT_VERSION in cf_version:
            return True

        print("WARNING: clang-format found in path, but incorrect version found at " +
                self.path + " with version: " + cf_version)

        return False

    def _lint(self, file_name, print_diff):
        """Check the specified file has the correct format
        """
        with open(file_name, 'rb') as original_text:
            original_file = original_text.read()

        # Get formatted file as clang-format would format the file
        formatted_file = callo([self.path, "--style=file", file_name])

        if original_file != formatted_file:
            if print_diff:
                original_lines = original_file.splitlines()
                formatted_lines = formatted_file.splitlines()
                result = difflib.unified_diff(original_lines, formatted_lines)

                # Take a lock to ensure diffs do not get mixed when printed to the screen
                with self.print_lock:
                    print("ERROR: Found diff for " + file_name)
                    print("To fix formatting errors, run %s --style=file -i %s" %
                            (self.path, file_name))
                    for line in result:
                        print(line.rstrip())

            return False

        return True

    def lint(self, file_name):
        """Check the specified file has the correct format
        """
        return self._lint(file_name, print_diff=True)

    def format(self, file_name):
        """Update the format of the specified file
        """
        if self._lint(file_name, print_diff=False):
            return True

        # Update the file with clang-format
        formatted = not subprocess.call([self.path, "--style=file", "-i", file_name])

        # Version 3.8 generates files like foo.cpp~RF83372177.TMP when it formats foo.cpp
        # on Windows, we must clean these up
        if sys.platform == "win32":
            glob_pattern = file_name + "*.TMP"
            for fglob in glob.glob(glob_pattern):
                os.unlink(fglob)

        return formatted


def parallel_process(items, func):
    """Run a set of work items to completion
    """
    try:
        cpus = cpu_count()
    except NotImplementedError:
        cpus = 1

    task_queue = Queue.Queue()

    # Use a list so that worker function will capture this variable
    pp_event = threading.Event()
    pp_result = [True]
    pp_lock = threading.Lock()

    def worker():
        """Worker thread to process work items in parallel
        """
        while not pp_event.is_set():
            try:
                item = task_queue.get_nowait()
            except Queue.Empty:
                # if the queue is empty, exit the worker thread
                pp_event.set()
                return

            try:
                ret = func(item)
            finally:
                # Tell the queue we finished with the item
                task_queue.task_done()

            # Return early if we fail, and signal we are done
            if not ret:
                with pp_lock:
                    pp_result[0] = False

                pp_event.set()
                return

    # Enqueue all the work we want to process
    for item in items:
        task_queue.put(item)

    # Process all the work
    threads = []
    for cpu in range(cpus):
        thread = threading.Thread(target=worker)

        thread.daemon = True
        thread.start()
        threads.append(thread)

    # Wait for the threads to finish
    # Loop with a timeout so that we can process Ctrl-C interrupts
    # Note: On Python 2.6 wait always returns None so we check is_set also,
    #  This works because we only set the event once, and never reset it
    while not pp_event.wait(1) and not pp_event.is_set():
        time.sleep(1)

    for thread in threads:
        thread.join()

    return pp_result[0]

def get_base_dir():
    """Get the base directory for mongo repo.
        This script assumes that it is running in buildscripts/, and uses
        that to find the base directory.
    """
    try:
        return subprocess.check_output(['git', 'rev-parse', '--show-toplevel']).rstrip()
    except:
        # We are not in a valid git directory. Use the script path instead.
        return os.path.dirname(os.path.dirname(os.path.realpath(__file__)))

def get_repos():
    """Get a list of Repos to check clang-format for
    """
    base_dir = get_base_dir()

    # Get a list of modules
    # TODO: how do we filter rocks, does it matter?
    mongo_modules = moduleconfig.discover_module_directories(
                        os.path.join(base_dir, MODULE_DIR), None)

    paths = [os.path.join(base_dir, MODULE_DIR, m) for m in mongo_modules]

    paths.append(base_dir)

    return [Repo(p) for p in paths]


class Repo(object):
    """Class encapsulates all knowledge about a git repository, and its metadata
        to run clang-format.
    """
    def __init__(self, path):
        self.path = path

        self.root = self._get_root()

    def _callgito(self, args):
        """Call git for this repository, and return the captured output
        """
        # These two flags are the equivalent of -C in newer versions of Git
        # but we use these to support versions pre 1.8.5 but it depends on the command
        # and what the current directory is
        return callo(['git', '--git-dir', os.path.join(self.path, ".git"),
                            '--work-tree', self.path] + args)

    def _callgit(self, args):
        """Call git for this repository without capturing output
        This is designed to be used when git returns non-zero exit codes.
        """
        # These two flags are the equivalent of -C in newer versions of Git
        # but we use these to support versions pre 1.8.5 but it depends on the command
        # and what the current directory is
        return subprocess.call(['git', '--git-dir', os.path.join(self.path, ".git"),
                                '--work-tree', self.path] + args)

    def _get_local_dir(self, path):
        """Get a directory path relative to the git root directory
        """
        if os.path.isabs(path):
            return os.path.relpath(path, self.root)
        return path

    def get_candidates(self, candidates):
        """Get the set of candidate files to check by querying the repository

        Returns the full path to the file for clang-format to consume.
        """
        if candidates is not None and len(candidates) > 0:
            candidates = [self._get_local_dir(f) for f in candidates]
            valid_files = list(set(candidates).intersection(self.get_candidate_files()))
        else:
            valid_files = list(self.get_candidate_files())

        # Get the full file name here
        valid_files = [os.path.normpath(os.path.join(self.root, f)) for f in valid_files]

        return valid_files

    def get_root(self):
        """Get the root directory for this repository
        """
        return self.root

    def _get_root(self):
        """Gets the root directory for this repository from git
        """
        gito = self._callgito(['rev-parse', '--show-toplevel'])

        return gito.rstrip()

    def _git_ls_files(self, cmd):
        """Run git-ls-files and filter the list of files to a valid candidate list
        """
        gito = self._callgito(cmd)

        # This allows us to pick all the interesting files
        # in the mongo and mongo-enterprise repos
        file_list = [line.rstrip()
                for line in gito.splitlines()
                    if (line.startswith("jstests") or line.startswith("src"))
                        and not line.startswith("src/third_party/")
                        and not line.startswith("src/mongo/gotools/")]

        files_match = re.compile('\\.(h|cpp|js)$')

        file_list = [a for a in file_list if files_match.search(a)]

        return file_list

    def get_candidate_files(self):
        """Query git to get a list of all files in the repo to consider for analysis
        """
        return self._git_ls_files(["ls-files", "--cached"])

    def get_working_tree_candidate_files(self):
        """Query git to get a list of all files in the working tree to consider for analysis
        """
        return self._git_ls_files(["ls-files", "--cached", "--others"])

    def get_working_tree_candidates(self):
        """Get the set of candidate files to check by querying the repository

        Returns the full path to the file for clang-format to consume.
        """
        valid_files = list(self.get_working_tree_candidate_files())

        # Get the full file name here
        valid_files = [os.path.normpath(os.path.join(self.root, f)) for f in valid_files]

        # Filter out files that git thinks exist but were removed.
        valid_files = [f for f in valid_files if os.path.exists(f)]

        return valid_files

    def is_detached(self):
        """Is the current working tree in a detached HEAD state?
        """
        # symbolic-ref returns 1 if the repo is in a detached HEAD state
        return self._callgit(["symbolic-ref", "--quiet", "HEAD"])

    def is_ancestor(self, parent, child):
        """Is the specified parent hash an ancestor of child hash?
        """
        # merge base returns 0 if parent is an ancestor of child
        return not self._callgit(["merge-base", "--is-ancestor", parent, child])

    def is_commit(self, sha1):
        """Is the specified hash a valid git commit?
        """
        # cat-file -e returns 0 if it is a valid hash
        return not self._callgit(["cat-file", "-e", "%s^{commit}" % sha1])

    def is_working_tree_dirty(self):
        """Does the current working tree have changes?
        """
        # diff returns 1 if the working tree has local changes
        return self._callgit(["diff", "--quiet"])

    def does_branch_exist(self, branch):
        """Does the branch exist?
        """
        # rev-parse returns 0 if the branch exists
        return not self._callgit(["rev-parse", "--verify", branch])

    def get_merge_base(self, commit):
        """Get the merge base between 'commit' and HEAD
        """
        return self._callgito(["merge-base", "HEAD", commit]).rstrip()

    def get_branch_name(self):
        """Get the current branch name, short form
           This returns "master", not "refs/head/master"
           Will not work if the current branch is detached
        """
        branch = self.rev_parse(["--abbrev-ref", "HEAD"])
        if branch == "HEAD":
            raise ValueError("Branch is currently detached")

        return branch

    def add(self, command):
        """git add wrapper
        """
        return self._callgito(["add"] + command)

    def checkout(self, command):
        """git checkout wrapper
        """
        return self._callgito(["checkout"] + command)

    def commit(self, command):
        """git commit wrapper
        """
        return self._callgito(["commit"] + command)

    def diff(self, command):
        """git diff wrapper
        """
        return self._callgito(["diff"] + command)

    def log(self, command):
        """git log wrapper
        """
        return self._callgito(["log"] + command)

    def rev_parse(self, command):
        """git rev-parse wrapper
        """
        return self._callgito(["rev-parse"] + command).rstrip()

    def rm(self, command):
        """git rm wrapper
        """
        return self._callgito(["rm"] + command)

    def show(self, command):
        """git show wrapper
        """
        return self._callgito(["show"] + command)

def get_list_from_lines(lines):
    """"Convert a string containing a series of lines into a list of strings
    """
    return [line.rstrip() for line in lines.splitlines()]

def get_files_to_check_working_tree():
    """Get a list of files to check form the working tree.
       This will pick up files not managed by git.
    """
    repos = get_repos()

    valid_files = list(itertools.chain.from_iterable([r.get_working_tree_candidates() for r in repos]))

    return valid_files

def get_files_to_check():
    """Get a list of files that need to be checked
       based on which files are managed by git.
    """
    repos = get_repos()

    valid_files = list(itertools.chain.from_iterable([r.get_candidates(None) for r in repos]))

    return valid_files

def get_files_to_check_from_patch(patches):
    """Take a patch file generated by git diff, and scan the patch for a list of files to check.
    """
    candidates = []

    # Get a list of candidate_files
    check = re.compile(r"^diff --git a\/([\w\/\.\-]+) b\/[\w\/\.\-]+")

    lines = []
    for patch in patches:
        with open(patch, "rb") as infile:
            lines += infile.readlines()

    candidates = [check.match(line).group(1) for line in lines if check.match(line)]

    repos = get_repos()

    valid_files = list(itertools.chain.from_iterable([r.get_candidates(candidates) for r in repos]))

    return valid_files

def _get_build_dir():
    """Get the location of the scons' build directory in case we need to download clang-format
    """
    return os.path.join(get_base_dir(), "build")

def _lint_files(clang_format, files):
    """Lint a list of files with clang-format
    """
    clang_format = ClangFormat(clang_format, _get_build_dir())

    lint_clean = parallel_process([os.path.abspath(f) for f in files], clang_format.lint)

    if not lint_clean:
        print("ERROR: Code Style does not match coding style")
        sys.exit(1)

def lint_patch(clang_format, infile):
    """Lint patch command entry point
    """
    files = get_files_to_check_from_patch(infile)

    # Patch may have files that we do not want to check which is fine
    if files:
        _lint_files(clang_format, files)

def lint(clang_format):
    """Lint files command entry point
    """
    files = get_files_to_check()

    _lint_files(clang_format, files)

    return True

def lint_all(clang_format):
    """Lint files command entry point based on working tree
    """
    files = get_files_to_check_working_tree()

    _lint_files(clang_format, files)

    return True

def _format_files(clang_format, files):
    """Format a list of files with clang-format
    """
    clang_format = ClangFormat(clang_format, _get_build_dir())

    format_clean = parallel_process([os.path.abspath(f) for f in files], clang_format.format)

    if not format_clean:
        print("ERROR: failed to format files")
        sys.exit(1)

def format_func(clang_format):
    """Format files command entry point
    """
    files = get_files_to_check()

    _format_files(clang_format, files)

def reformat_branch(clang_format, commit_prior_to_reformat, commit_after_reformat):
    """Reformat a branch made before a clang-format run
    """
    clang_format = ClangFormat(clang_format, _get_build_dir())

    if os.getcwd() != get_base_dir():
        raise ValueError("reformat-branch must be run from the repo root")

    if not os.path.exists("buildscripts/clang_format.py"):
        raise ValueError("reformat-branch is only supported in the mongo repo")

    repo = Repo(get_base_dir())

    # Validate that user passes valid commits
    if not repo.is_commit(commit_prior_to_reformat):
        raise ValueError("Commit Prior to Reformat '%s' is not a valid commit in this repo" %
                commit_prior_to_reformat)

    if not repo.is_commit(commit_after_reformat):
        raise ValueError("Commit After Reformat '%s' is not a valid commit in this repo" %
                commit_after_reformat)

    if not repo.is_ancestor(commit_prior_to_reformat, commit_after_reformat):
        raise ValueError(("Commit Prior to Reformat '%s' is not a valid ancestor of Commit After" +
                " Reformat '%s' in this repo") % (commit_prior_to_reformat, commit_after_reformat))

    # Validate the user is on a local branch that has the right merge base
    if repo.is_detached():
        raise ValueError("You must not run this script in a detached HEAD state")

    # Validate the user has no pending changes
    if repo.is_working_tree_dirty():
        raise ValueError("Your working tree has pending changes. You must have a clean working tree before proceeding.")

    merge_base = repo.get_merge_base(commit_prior_to_reformat)

    if not merge_base == commit_prior_to_reformat:
        raise ValueError("Please rebase to '%s' and resolve all conflicts before running this script" % (commit_prior_to_reformat))

    # We assume the target branch is master, it could be a different branch if needed for testing
    merge_base = repo.get_merge_base("master")

    if not merge_base == commit_prior_to_reformat:
        raise ValueError("This branch appears to already have advanced too far through the merge process")

    # Everything looks good so lets start going through all the commits
    branch_name = repo.get_branch_name()
    new_branch = "%s-reformatted" % branch_name

    if repo.does_branch_exist(new_branch):
        raise ValueError("The branch '%s' already exists. Please delete the branch '%s', or rename the current branch." % (new_branch, new_branch))

    commits = get_list_from_lines(repo.log(["--reverse", "--pretty=format:%H", "%s..HEAD" % commit_prior_to_reformat]))

    previous_commit_base = commit_after_reformat

    files_match = re.compile('\\.(h|cpp|js)$')

    # Go through all the commits the user made on the local branch and migrate to a new branch
    # that is based on post_reformat commits instead
    for commit_hash in commits:
        repo.checkout(["--quiet", commit_hash])

        deleted_files = []

        # Format each of the files by checking out just a single commit from the user's branch
        commit_files = get_list_from_lines(repo.diff(["HEAD~", "--name-only"]))

        for commit_file in commit_files:

            # Format each file needed if it was not deleted
            if not os.path.exists(commit_file):
                print("Skipping file '%s' since it has been deleted in commit '%s'" % (
                        commit_file, commit_hash))
                deleted_files.append(commit_file)
                continue

            if files_match.search(commit_file):
                clang_format.format(commit_file)
            else:
                print("Skipping file '%s' since it is not a file clang_format should format" %
                        commit_file)

        # Check if anything needed reformatting, and if so amend the commit
        if not repo.is_working_tree_dirty():
            print ("Commit %s needed no reformatting" % commit_hash)
        else:
            repo.commit(["--all", "--amend", "--no-edit"])

        # Rebase our new commit on top the post-reformat commit
        previous_commit = repo.rev_parse(["HEAD"])

        # Checkout the new branch with the reformatted commits
        # Note: we will not name as a branch until we are done with all commits on the local branch
        repo.checkout(["--quiet", previous_commit_base])

        # Copy each file from the reformatted commit on top of the post reformat
        diff_files = get_list_from_lines(repo.diff(["%s~..%s" % (previous_commit, previous_commit),
            "--name-only"]))

        for diff_file in diff_files:
            # If the file was deleted in the commit we are reformatting, we need to delete it again
            if diff_file in deleted_files:
                repo.rm([diff_file])
                continue

            # The file has been added or modified, continue as normal
            file_contents = repo.show(["%s:%s" % (previous_commit, diff_file)])

            root_dir = os.path.dirname(diff_file)
            if root_dir and not os.path.exists(root_dir):
                os.makedirs(root_dir)

            with open(diff_file, "w+") as new_file:
                new_file.write(file_contents)

            repo.add([diff_file])

        # Create a new commit onto clang-formatted branch
        repo.commit(["--reuse-message=%s" % previous_commit])

        previous_commit_base = repo.rev_parse(["HEAD"])

    # Create a new branch to mark the hashes we have been using
    repo.checkout(["-b", new_branch])

    print("reformat-branch is done running.\n")
    print("A copy of your branch has been made named '%s', and formatted with clang-format.\n" % new_branch)
    print("The original branch has been left unchanged.")
    print("The next step is to rebase the new branch on 'master'.")


def usage():
    """Print usage
    """
    print("clang-format.py supports 5 commands [ lint, lint-all, lint-patch, format, reformat-branch].")

def main():
    """Main entry point
    """
    parser = OptionParser()
    parser.add_option("-c", "--clang-format", type="string", dest="clang_format")

    (options, args) = parser.parse_args(args=sys.argv)

    if len(args) > 1:
        command = args[1]

        if command == "lint":
            lint(options.clang_format)
        elif command == "lint-all":
            lint_all(options.clang_format)
        elif command == "lint-patch":
            lint_patch(options.clang_format, args[2:])
        elif command == "format":
            format_func(options.clang_format)
        elif command == "reformat-branch":

            if len(args) < 3:
                print("ERROR: reformat-branch takes two parameters: commit_prior_to_reformat commit_after_reformat")
                return

            reformat_branch(options.clang_format, args[2], args[3])
        else:
            usage()
    else:
        usage()

if __name__ == "__main__":
    main()