diff -r 22683f2f8100 -r bd5c4320b5a8 mercurial/commands.py
--- a/mercurial/commands.py	Wed Aug 17 21:00:11 2016 -0700
+++ b/mercurial/commands.py	Wed Aug 17 21:01:02 2016 -0700
@@ -1858,107 +1858,6 @@
     with repo.wlock(False):
         return cmdutil.copy(ui, repo, pats, opts)
 
-@command('debugdeltachain',
-    debugrevlogopts + formatteropts,
-    _('-c|-m|FILE'),
-    optionalrepo=True)
-def debugdeltachain(ui, repo, file_=None, **opts):
-    """dump information about delta chains in a revlog
-
-    Output can be templatized. Available template keywords are:
-
-    :``rev``:       revision number
-    :``chainid``:   delta chain identifier (numbered by unique base)
-    :``chainlen``:  delta chain length to this revision
-    :``prevrev``:   previous revision in delta chain
-    :``deltatype``: role of delta / how it was computed
-    :``compsize``:  compressed size of revision
-    :``uncompsize``: uncompressed size of revision
-    :``chainsize``: total size of compressed revisions in chain
-    :``chainratio``: total chain size divided by uncompressed revision size
-                    (new delta chains typically start at ratio 2.00)
-    :``lindist``:   linear distance from base revision in delta chain to end
-                    of this revision
-    :``extradist``: total size of revisions not part of this delta chain from
-                    base of delta chain to end of this revision; a measurement
-                    of how much extra data we need to read/seek across to read
-                    the delta chain for this revision
-    :``extraratio``: extradist divided by chainsize; another representation of
-                    how much unrelated data is needed to load this delta chain
-    """
-    r = cmdutil.openrevlog(repo, 'debugdeltachain', file_, opts)
-    index = r.index
-    generaldelta = r.version & revlog.REVLOGGENERALDELTA
-
-    def revinfo(rev):
-        e = index[rev]
-        compsize = e[1]
-        uncompsize = e[2]
-        chainsize = 0
-
-        if generaldelta:
-            if e[3] == e[5]:
-                deltatype = 'p1'
-            elif e[3] == e[6]:
-                deltatype = 'p2'
-            elif e[3] == rev - 1:
-                deltatype = 'prev'
-            elif e[3] == rev:
-                deltatype = 'base'
-            else:
-                deltatype = 'other'
-        else:
-            if e[3] == rev:
-                deltatype = 'base'
-            else:
-                deltatype = 'prev'
-
-        chain = r._deltachain(rev)[0]
-        for iterrev in chain:
-            e = index[iterrev]
-            chainsize += e[1]
-
-        return compsize, uncompsize, deltatype, chain, chainsize
-
-    fm = ui.formatter('debugdeltachain', opts)
-
-    fm.plain('    rev  chain# chainlen     prev   delta       '
-             'size    rawsize  chainsize     ratio   lindist extradist '
-             'extraratio\n')
-
-    chainbases = {}
-    for rev in r:
-        comp, uncomp, deltatype, chain, chainsize = revinfo(rev)
-        chainbase = chain[0]
-        chainid = chainbases.setdefault(chainbase, len(chainbases) + 1)
-        basestart = r.start(chainbase)
-        revstart = r.start(rev)
-        lineardist = revstart + comp - basestart
-        extradist = lineardist - chainsize
-        try:
-            prevrev = chain[-2]
-        except IndexError:
-            prevrev = -1
-
-        chainratio = float(chainsize) / float(uncomp)
-        extraratio = float(extradist) / float(chainsize)
-
-        fm.startitem()
-        fm.write('rev chainid chainlen prevrev deltatype compsize '
-                 'uncompsize chainsize chainratio lindist extradist '
-                 'extraratio',
-                 '%7d %7d %8d %8d %7s %10d %10d %10d %9.5f %9d %9d %10.5f\n',
-                 rev, chainid, len(chain), prevrev, deltatype, comp,
-                 uncomp, chainsize, chainratio, lineardist, extradist,
-                 extraratio,
-                 rev=rev, chainid=chainid, chainlen=len(chain),
-                 prevrev=prevrev, deltatype=deltatype, compsize=comp,
-                 uncompsize=uncomp, chainsize=chainsize,
-                 chainratio=chainratio, lindist=lineardist,
-                 extradist=extradist, extraratio=extraratio)
-
-    fm.end()
-
 @command('debuginstall', [] + formatteropts, '', norepo=True)
 def debuginstall(ui, **opts):
     '''test Mercurial installation