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

[Kostia Balytskyi]

# 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)
+        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
+
     def mergemarkers(self, transaction, data):
         """merge a binary stream of markers inside the obsstore