Create "git cache" command.

git_cache.py

Index: git_cache.py
diff --git a/git_cache.py b/git_cache.py
new file mode 100755
index 0000000000000000000000000000000000000000..77463a6013780b98e6e63b91bb082a1b6947a7a3
--- /dev/null
+++ b/git_cache.py
@@ -0,0 +1,303 @@
+#!/usr/bin/env python
+# Copyright 2014 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""A git command for managing a local cache of git repositories."""
+
+import errno
+import logging
+import optparse
+import os
+import tempfile
+import subprocess
+import sys
+import urlparse
+
+import gclient_utils
+import subcommand
+
+
+GIT_EXECUTABLE = 'git.bat' if sys.platform.startswith('win') else 'git'
+
+
+def NormalizeUrl(url):
+  """Convert a git url to a normalized form."""
+  parsed = urlparse.urlparse(url)
+  norm_url = 'https://' + parsed.netloc + parsed.path
+  if not norm_url.endswith('.git'):
+    norm_url += '.git'
+  return norm_url
+
+
+def UrlToCacheDir(url):
+  """Convert a git url to a normalized form for the cache dir path."""
+  parsed = urlparse.urlparse(url)
+  norm_url = parsed.netloc + parsed.path
+  if norm_url.endswith('.git'):
+    norm_url = norm_url[:-len('.git')]
+  return norm_url.replace('-', '--').replace('/', '-').lower()
+
+
+def RunGit(cmd, **kwargs):
+  """Run git in a subprocess."""
+  kwargs.setdefault('cwd', os.getcwd())
+  if kwargs.get('filter_fn'):
+    kwargs['filter_fn'] = gclient_utils.GitFilter(kwargs.get('filter_fn'))
+    kwargs.setdefault('print_stdout', False)
+    env = kwargs.get('env') or kwargs.setdefault('env', os.environ.copy())
+    env.setdefault('GIT_ASKPASS', 'true')
+    env.setdefault('SSH_ASKPASS', 'true')
+  else:
+    kwargs.setdefault('print_stdout', True)
+  stdout = kwargs.get('stdout', sys.stdout)
+  print >> stdout, 'running "git %s" in "%s"' % (' '.join(cmd), kwargs['cwd'])
+  gclient_utils.CheckCallAndFilter([GIT_EXECUTABLE] + cmd, **kwargs)
+
+
+class LockError(Exception):
+  pass
+
+
+class Lockfile(object):
+  """Class to represent a cross-platform process-specific lockfile."""
+
+  def __init__(self, path):
+    self.path = os.path.abspath(path)
+    self.lockfile = self.path + ".lock"
+    self.pid = os.getpid()
+
+  def _read_pid(self):
+    """Read the pid stored in the lockfile.
+
+    Note: This method is potentially racy. By the time it returns the lockfile
+    may have been unlocked, removed, or stolen by some other process.
+    """
+    try:
+      with open(self.lockfile, 'r') as f:
+        pid = int(f.readline().strip())
+    except (IOError, ValueError):
+      pid = None
+    return pid
+
+  def _make_lockfile(self):
+    """Safely creates a lockfile containing the current pid."""
+    open_flags = (os.O_CREAT | os.O_EXCL | os.O_WRONLY)
+    fd = os.open(self.lockfile, open_flags, 0o644)
+    f = os.fdopen(fd, 'w')
+    print >> f, self.pid
+    f.close()
+
+  def _remove_lockfile(self):
+    """Delete the lockfile. Complains (implicitly) if it doesn't exist."""
+    os.remove(self.lockfile)
+
+  def lock(self):
+    """Acquire the lock.
+
+    Note: This is a NON-BLOCKING FAIL-FAST operation.
+    Do. Or do not. There is no try.
+    """
+    try:
+      self._make_lockfile()
+    except OSError as e:
+      if e.errno == errno.EEXIST:
+        raise LockError("%s is already locked" % self.path)
+      else:
+        raise LockError("Failed to create %s (err %s)" % (self.path, e.errno))
+
+  def unlock(self):
+    """Release the lock."""
+    if not self.is_locked():
+      raise LockError("%s is not locked" % self.path)
+    if not self.i_am_locking():
+      raise LockError("%s is locked, but not by me" % self.path)
+    self._remove_lockfile()
+
+  def break_lock(self):
+    """Remove the lock, even if it was created by someone else."""
+    try:
+      self._remove_lockfile()
+      return True
+    except OSError as exc:
+      if exc.errno == errno.ENOENT:
+        return False
+      else:
+        raise
+
+  def is_locked(self):
+    """Test if the file is locked by anyone.
+
+    Note: This method is potentially racy. By the time it returns the lockfile
+    may have been unlocked, removed, or stolen by some other process.
+    """
+    return os.path.exists(self.lockfile)
+
+  def i_am_locking(self):
+    """Test if the file is locked by this process."""
+    return self.is_locked() and self.pid == self._read_pid()
+
+  def __enter__(self):
+    self.lock()
+    return self
+
+  def __exit__(self, *_exc):
+    self.unlock()
+
+
+@subcommand.usage('[url of repo to check for caching]')
+def CMDexists(parser, args):
+  """Check to see if there already is a cache of the given repo."""
+  options, args = parser.parse_args(args)
+  if not len(args) == 1:
+    parser.error('git cache exists only takes exactly one repo url.')
+  url = args[0]
+  repo_dir = os.path.join(options.cache_dir, UrlToCacheDir(url))
+  flag_file = os.path.join(repo_dir, 'config')
+  if os.path.isdir(repo_dir) and os.path.isfile(flag_file):
+    print repo_dir
+    return 0
+  return 1
+
+
+@subcommand.usage('[url of repo to add to or update in cache]')
+def CMDpopulate(parser, args):
+  """Ensure that the cache has all up-to-date objects for the given repo."""
+  parser.add_option('--depth', type='int',
+                    help='Only cache DEPTH commits of history')
+  parser.add_option('--shallow', '-s', action='store_true',
+                    help='Only cache 10000 commits of history')
+  parser.add_option('--ref', action='append',
+                    help='Specify additional refs to be fetched')
+  options, args = parser.parse_args(args)
+  if options.shallow and not options.depth:
+    options.depth = 10000
+  if not len(args) == 1:
+    parser.error('git cache populate only takes exactly one repo url.')
+  url = args[0]
+
+  gclient_utils.safe_makedirs(options.cache_dir)
+  repo_dir = os.path.join(options.cache_dir, UrlToCacheDir(url))
+
+  v = []
+  filter_fn = lambda l: '[up to date]' not in l
+  if options.verbose:
+    v = ['-v', '--progress']
+    filter_fn = None
+
+  d = []
+  if options.depth:
+    d = ['--depth', '%d' % options.depth]
+
+  def _config(directory):
+    RunGit(['config', 'core.deltaBaseCacheLimit', '2g'],
+           cwd=directory)
+    RunGit(['config', 'remote.origin.url', NormalizeUrl(url)],
+           cwd=directory)
+    RunGit(['config', '--replace-all', 'remote.origin.fetch',
+            '+refs/heads/*:refs/heads/*'],
+           cwd=directory)
+    for ref in options.ref or []:
+      ref = ref.rstrip('/')
+      refspec = '+refs/%s/*:refs/%s/*' % (ref, ref)
+      RunGit(['config', '--add', 'remote.origin.fetch', refspec],
+             cwd=directory)
+
+  with Lockfile(repo_dir):
+    # Setup from scratch if the repo is new or is in a bad state.
+    if not os.path.exists(os.path.join(repo_dir, 'config')):
+      gclient_utils.rmtree(repo_dir)
+      tempdir = tempfile.mkdtemp(suffix=UrlToCacheDir(url),
+                                 dir=options.cache_dir)
+      RunGit(['init', '--bare'], cwd=tempdir)
+      _config(tempdir)
+      fetch_cmd = ['fetch'] + v + d + ['--tags', 'origin']
+      RunGit(fetch_cmd, filter_fn=filter_fn, cwd=tempdir, retry=True)
+      os.rename(tempdir, repo_dir)
+    else:
+      _config(repo_dir)
+      if options.depth and os.path.exists(os.path.join(repo_dir, 'shallow')):
+        logging.warn('Shallow fetch requested, but repo cache already exists.')
+      fetch_cmd = ['fetch'] + v + ['--update-shallow', '--tags', 'origin']
+      RunGit(fetch_cmd, filter_fn=filter_fn, cwd=repo_dir, retry=True)
+
+
+@subcommand.usage('[url of repo to unlock, or -a|--all]')
+def CMDunlock(parser, args):
+  """Unlock one or all repos if their lock files are still around."""
+  parser.add_option('--force', '-f', action='store_true',
+                    help='Actually perform the action')
+  parser.add_option('--all', '-a', action='store_true',
+                    help='Unlock all repository caches')
+  options, args = parser.parse_args(args)
+  if len(args) > 1 or (len(args) == 0 and not options.all):
+    parser.error('git cache unlock takes exactly one repo url, or --all')
+
+  if not options.all:
+    url = args[0]
+    repo_dirs = [os.path.join(options.cache_dir, UrlToCacheDir(url))]
+  else:
+    repo_dirs = [path for path in os.listdir(options.cache_dir)
+                 if os.path.isdir(path)]
+  lockfiles = [repo_dir + '.lock' for repo_dir in repo_dirs
+               if os.path.exists(repo_dir + '.lock')]
+
+  if not options.force:
+    parser.error('git cache unlock requires -f|--force to do anything. '
+                 'Refusing to unlock the following repo caches: '
+                 ', '.join(lockfiles))
+
+  unlocked = []
+  untouched = []
+  for repo_dir in repo_dirs:
+    lf = Lockfile(repo_dir)
+    if lf.break_lock():
+      unlocked.append(repo_dir)
+    else:
+      untouched.append(repo_dir)
+
+  if unlocked:
+    logging.info('Broke locks on these caches: %s' % unlocked)
+  if untouched:
+    logging.debug('Did not touch these caches: %s' % untouched)
+
+
+class OptionParser(optparse.OptionParser):
+  """Wrapper class for OptionParser to handle global options."""
+
+  def __init__(self, *args, **kwargs):
+    optparse.OptionParser.__init__(self, *args, prog='git cache', **kwargs)
+    self.add_option('-c', '--cache-dir',
+                    help='Path to the directory containing the cache')
+    self.add_option('-v', '--verbose', action='count', default=0,
+                    help='Increase verbosity (can be passed multiple times)')
+
+  def parse_args(self, args=None, values=None):
+    options, args = optparse.OptionParser.parse_args(self, args, values)
+
+    try:
+      global_cache_dir = subprocess.check_output(
+          [GIT_EXECUTABLE, 'config', '--global', 'cache.cachepath']).strip()
+      if options.cache_dir:
+        logging.warn('Overriding globally-configured cache directory.')
+      else:
+        options.cache_dir = global_cache_dir
+    except subprocess.CalledProcessError:
+      if not options.cache_dir:
+        self.error('No cache directory specified on command line '
+                   'or in cache.cachepath.')
+    options.cache_dir = os.path.abspath(options.cache_dir)
+
+    levels = [logging.WARNING, logging.INFO, logging.DEBUG]
+    logging.basicConfig(level=levels[min(options.verbose, len(levels) - 1)])
+
+    return options, args
+
+
+def main(argv):
+  dispatcher = subcommand.CommandDispatcher(__name__)
+  return dispatcher.execute(OptionParser(), argv)
+
+
+if __name__ == '__main__':
+  sys.exit(main(sys.argv[1:]))