view mercurial/lock.py @ 13950:14d0553bd48b

help: do not show full help text for command on option errors

Example

  $ hg clone --jump foo bar
  hg clone: option --jump not recognized
  hg clone [OPTION]... SOURCE [DEST]

  make a copy of an existing repository

  options:

   -U --noupdate           the clone will include an empty working copy (only a
                           repository)
   -u --updaterev REV      revision, tag or branch to check out
   -r --rev REV [+]        include the specified changeset
   -b --branch BRANCH [+]  clone only the specified branch
      --pull               use pull protocol to copy metadata
      --uncompressed       use uncompressed transfer (fast over LAN)
   -e --ssh CMD            specify ssh command to use
      --remotecmd CMD      specify hg command to run on the remote side
      --insecure           do not verify server certificate (ignoring
                           web.cacerts config)

  [+] marked option can be specified multiple times

  use "hg help clone" to show the full help text

Motivation for this change

  If the user already has specified the command, he probably already knows
  the command to some extent. Apparently, he has a problem with the options,
  so we show him just the synopsis with the short help and the details about
  the options, with a hint on the last line how to get the full help text.

Why is Mercurial better with this change?

  Experts who just forgot about the details of an option don't get that
  much text thrown at them, while the newbies still get a hint on the last
  line how to get the full help text.

# lock.py - simple advisory locking scheme for mercurial
#
# Copyright 2005, 2006 Matt Mackall <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

import util, error
import errno, os, socket, time
import warnings

class lock(object):
    '''An advisory lock held by one process to control access to a set
    of files.  Non-cooperating processes or incorrectly written scripts
    can ignore Mercurial's locking scheme and stomp all over the
    repository, so don't do that.

    Typically used via localrepository.lock() to lock the repository
    store (.hg/store/) or localrepository.wlock() to lock everything
    else under .hg/.'''

    # lock is symlink on platforms that support it, file on others.

    # symlink is used because create of directory entry and contents
    # are atomic even over nfs.

    # old-style lock: symlink to pid
    # new-style lock: symlink to hostname:pid

    _host = None

    def __init__(self, file, timeout=-1, releasefn=None, desc=None):
        self.f = file
        self.held = 0
        self.timeout = timeout
        self.releasefn = releasefn
        self.desc = desc
        self.lock()

    def __del__(self):
        if self.held:
            warnings.warn("use lock.release instead of del lock",
                    category=DeprecationWarning,
                    stacklevel=2)

            # ensure the lock will be removed
            # even if recursive locking did occur
            self.held = 1

        self.release()

    def lock(self):
        timeout = self.timeout
        while 1:
            try:
                self.trylock()
                return 1
            except error.LockHeld, inst:
                if timeout != 0:
                    time.sleep(1)
                    if timeout > 0:
                        timeout -= 1
                    continue
                raise error.LockHeld(errno.ETIMEDOUT, inst.filename, self.desc,
                                     inst.locker)

    def trylock(self):
        if self.held:
            self.held += 1
            return
        if lock._host is None:
            lock._host = socket.gethostname()
        lockname = '%s:%s' % (lock._host, os.getpid())
        while not self.held:
            try:
                util.makelock(lockname, self.f)
                self.held = 1
            except (OSError, IOError), why:
                if why.errno == errno.EEXIST:
                    locker = self.testlock()
                    if locker is not None:
                        raise error.LockHeld(errno.EAGAIN, self.f, self.desc,
                                             locker)
                else:
                    raise error.LockUnavailable(why.errno, why.strerror,
                                                why.filename, self.desc)

    def testlock(self):
        """return id of locker if lock is valid, else None.

        If old-style lock, we cannot tell what machine locker is on.
        with new-style lock, if locker is on this machine, we can
        see if locker is alive.  If locker is on this machine but
        not alive, we can safely break lock.

        The lock file is only deleted when None is returned.

        """
        locker = util.readlock(self.f)
        try:
            host, pid = locker.split(":", 1)
        except ValueError:
            return locker
        if host != lock._host:
            return locker
        try:
            pid = int(pid)
        except ValueError:
            return locker
        if util.testpid(pid):
            return locker
        # if locker dead, break lock.  must do this with another lock
        # held, or can race and break valid lock.
        try:
            l = lock(self.f + '.break', timeout=0)
            util.unlink(self.f)
            l.release()
        except error.LockError:
            return locker

    def release(self):
        if self.held > 1:
            self.held -= 1
        elif self.held == 1:
            self.held = 0
            if self.releasefn:
                self.releasefn()
            try:
                util.unlink(self.f)
            except OSError:
                pass

def release(*locks):
    for lock in locks:
        if lock is not None:
            lock.release()