mercurial/error.py

rollback: avoid unsafe rollback when not at tip (issue2998)

You can get into trouble if you commit, update back to an older
changeset, and then rollback. The update removes your valuable changes
from the working dir, then rollback removes them history. Oops: you've
just irretrievably lost data running nothing but core Mercurial
commands. (More subtly: rollback from a shared clone that was already
at an older changeset -- no update required, just rollback from the
wrong directory.)

The fix assumes that only "commit" transactions have irreplaceable
data, and allows rolling back non-commit transactions as always. But
when rolling back a commit, check that the working dir is checked out
to tip, i.e. the changeset we're about to destroy. If not, abort. You
can get back the old (dangerous) behaviour with --force.

# error.py - Mercurial exceptions
#
# Copyright 2005-2008 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.

"""Mercurial exceptions.

This allows us to catch exceptions at higher levels without forcing
imports.
"""

# Do not import anything here, please

class RevlogError(Exception):
    pass

class LookupError(RevlogError, KeyError):
    def __init__(self, name, index, message):
        self.name = name
        if isinstance(name, str) and len(name) == 20:
            from node import short
            name = short(name)
        RevlogError.__init__(self, '%s@%s: %s' % (index, name, message))

    def __str__(self):
        return RevlogError.__str__(self)

class CommandError(Exception):
    """Exception raised on errors in parsing the command line."""

class Abort(Exception):
    """Raised if a command needs to print an error and exit."""
    def __init__(self, *args, **kw):
        Exception.__init__(self, *args)
        self.hint = kw.get('hint')

class ConfigError(Abort):
    'Exception raised when parsing config files'

class OutOfBandError(Exception):
    'Exception raised when a remote repo reports failure'

class ParseError(Exception):
    'Exception raised when parsing config files (msg[, pos])'

class RepoError(Exception):
    def __init__(self, *args, **kw):
        Exception.__init__(self, *args)
        self.hint = kw.get('hint')

class RepoLookupError(RepoError):
    pass

class CapabilityError(RepoError):
    pass

class RequirementError(RepoError):
    """Exception raised if .hg/requires has an unknown entry."""
    pass

class LockError(IOError):
    def __init__(self, errno, strerror, filename, desc):
        IOError.__init__(self, errno, strerror, filename)
        self.desc = desc

class LockHeld(LockError):
    def __init__(self, errno, filename, desc, locker):
        LockError.__init__(self, errno, 'Lock held', filename, desc)
        self.locker = locker

class LockUnavailable(LockError):
    pass

class ResponseError(Exception):
    """Raised to print an error with part of output and exit."""

class UnknownCommand(Exception):
    """Exception raised if command is not in the command table."""

class AmbiguousCommand(Exception):
    """Exception raised if command shortcut matches more than one command."""

# derived from KeyboardInterrupt to simplify some breakout code
class SignalInterrupt(KeyboardInterrupt):
    """Exception raised on SIGTERM and SIGHUP."""

class SignatureError(Exception):
    pass