git pre-commit hook

#!/usr/bin/env python

import sys
import subprocess
import os
import re

def syscmd(*args, **kw):
    fail_ok = kw.get('fail_ok', False)
    p = subprocess.Popen(args, stdout=subprocess.PIPE)
    out, _ = p.communicate()
    if not fail_ok and p.returncode != 0:
        raise RuntimeError('%s # failed: %s' % (' '.join(args), p.returncode))
    return out

def checkline(line, report_error, ext=None):
    if re.search(r'console\.log', line):
        report_error('console.log: %s' % line)

    if re.search(r'print[^\n]+', line):
        report_error('print statement: %s' % line)

    if ext in ('js', 'py'):
        if re.search(r'\s$', line):
            report_error('Trailing whitespace: %s' % line)

def checkfile(filename, report_error):
    if filename.endswith('py'):
        out = syscmd('bin/django-lint', '-e', filename)

    if filename.startswith('media') and filename.endswith('js'):
        p = subprocess.Popen(
            ['bin/jslint', filename],
            stdout=subprocess.PIPE
        )
        out, _ = p.communicate()
        if 'No problems found in' not in out:
            report_error('JSlint errors', filename=filename)
            print >> sys.stderr, out

def difflines():
    diff = syscmd('git', 'diff', '--cached', '-M')
    filename = None
    lineno = None
    for line in diff.split('\n'):
        m = re.match(r'^diff --git a/(.*) b/\1$', line)
        if m:
            filename = m.group(1)
            continue
        m = re.match(r'@@ -\S+ \+(\d+)', line)
        if m:
            lineno = int(m.group(1)) - 1
            continue
        if line.startswith('+++'):
            continue
        if line.startswith(' '):
            lineno += 1
            continue
        if line.startswith('+'):
            lineno += 1
            yield line, filename, lineno

def check(report_error):
    if os.environ.get('SKIPCHECKS'):
        sys.exit(0)

    status = syscmd('git', 'status', fail_ok=True)
    if 'Untracked files:' in status:
        report_error('Untracked files')

    filenames = set()
    ext = None
    for line, filename, lineno in difflines():
        ext = filename.partition('.')[2]
        filenames.add(filename)
        checkline(line, lambda why: report_error(why, lineno, filename), ext)

    if not os.environ.get('SKIPLINT'):
        for filename in sorted(filenames):
            checkfile(filename, report_error)

fail = False
def run():
    def report_error(why, line=None, filename=None):
        global fail
        if not fail:
            print >> sys.stderr, "*"
            print >> sys.stderr, "* Errors found:"
            print >> sys.stderr, "*"
        print >> sys.stderr, "* %s" % why
        if line or filename:
            extra = '' + ('line %d ' % line if line else '') + \
                ('in %s' % filename if filename else '')
            print >> sys.stderr, "* %s" % extra
        print "*"
        fail = True

    check(report_error)

    return int(fail)

sys.exit(run())