[PATCH 2 of 2] commands: allow debugobsolete to delete arbitrary obsmarkers

[timeless]

Because someone else might read the value and operate based on it.

We don't want to try to operate on this object if they're using it. So
we should wait for them to finish, then get the lock to prevent the
next person from relying on it.

On Fri, Apr 1, 2016 at 2:36 PM, Kostia Balytskyi <ikostia at fb.com> wrote:
>
>
>
>
>
> On 4/1/16, 7:31 PM, "Pierre-Yves David" <pierre-yves.david at ens-lyon.org> wrote:
>
>>
>>
>>On 04/01/2016 08:56 AM, Kostia Balytskyi wrote:
>>> # HG changeset patch
>>> # User Kostia Balytskyi <ikostia at fb.com>
>>> # Date 1459525644 25200
>>> #      Fri Apr 01 08:47:24 2016 -0700
>>> # Node ID ff46f27e8fca7b726cc042eb745e54a3bc9dbe39
>>> # Parent  d4fc1ec31c6666d85eb2e8c174f6c231546ad8fd
>>> commands: allow debugobsolete to delete arbitrary obsmarkers
>>>
>>> Sample usage is:
>>>    '$ hg debugobsolete --delete 0 5'
>>>
>>> This is a debug feature that will help people working on evolution and
>>> obsolescense.
>>>
>>> diff --git a/mercurial/commands.py b/mercurial/commands.py
>>> --- a/mercurial/commands.py
>>> +++ b/mercurial/commands.py
>>> @@ -3046,6 +3046,7 @@ def debuglocks(ui, repo, **opts):
>>>             _('record parent information for the precursor')),
>>>            ('r', 'rev', [], _('display markers relevant to REV')),
>>>            ('', 'index', False, _('display index of the marker')),
>>> +         ('', 'delete', [], _('delete markers specified by indices')),
>>>           ] + commitopts2,
>>>            _('[OBSOLETED [REPLACEMENT ...]]'))
>>>   def debugobsolete(ui, repo, precursor=None, *successors, **opts):
>>> @@ -3066,6 +3067,16 @@ def debugobsolete(ui, repo, precursor=No
>>>               raise error.Abort('changeset references must be full hexadecimal '
>>>                                'node identifiers')
>>>
>>> +    if opts.get('delete'):
>>> +        try:
>>> +            indices = [int(v) for v in opts.get('delete')]
>>> +        except ValueError:
>>> +            raise error.Abort(_('invalid index value'),
>>> +                              hint=_('use integers fro indices'))
>>> +        n = repo.obsstore.delete(indices)
>>
>>We'll want some locking around this to prevent other process reading the
>>repository to misbehave.
>>
>>> +        ui.write(_('Deleted %i obsolescense markers\n') % n)
>>> +        return
>>> +
>>>       if precursor is not None:
>>>           if opts['rev']:
>>>               raise error.Abort('cannot select revision when creating marker')
>>> diff --git a/mercurial/obsolete.py b/mercurial/obsolete.py
>>> --- a/mercurial/obsolete.py
>>> +++ b/mercurial/obsolete.py
>>> @@ -633,6 +633,30 @@ class obsstore(object):
>>>           transaction.hookargs['new_obsmarkers'] = str(previous + len(new))
>>>           return len(new)
>>>
>>> +    def delete(self, indices):
>>> +        """Delete some obsmarkers from store and return the number of them
>>> +
>>> +        Indices is a list of ints which are the indices
>>> +        of the markers to be deleted."""
>>> +        if not indices:
>>> +            # we don't want to rewrite the obsstore with the same content
>>> +            return
>>> +
>>> +        left = []
>>> +        current = self._all
>>> +        n = 0
>>> +        for i, m in enumerate(current):
>>> +            if i in indices:
>>> +                n += 1
>>> +                continue
>>> +            left.append(m)
>>> +
>>> +        newobsstore = self.svfs('obsstore', 'w', atomictemp=True)
>>> +        for bytes in encodemarkers(left, True, self._version):
>>> +            newobsstore.write(bytes)
>>> +        newobsstore.close()
>>> +        return n
>>> +
>>
>>We probably want to have this somewhat collaborating with the
>>transaction, like mercurial.repair.strip do. At least we want to ensure
>>we are not in a transaction before butchering the obstore.
>
> Why do we want transaction if we're writing to the atomictemp file? AFAIK,
> it will write the new stuff into a temporary file and atomically rename it
> when we call close. Why isn't it good enough?
>
>>
>>(and that we are locked)
>>
>>>       def mergemarkers(self, transaction, data):
>>>           """merge a binary stream of markers inside the obsstore
>>
>>
>>--
>>Pierre-Yves David
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