mmap: backed out changeset 875d2af8cb4e stable

mmap: backed out changeset 875d2af8cb4e

There have been concrete and theoretical issues raised, this will need more
work during the next cycle.

--- a/mercurial/configitems.py	Fri Jan 18 16:02:26 2019 +0100
+++ b/mercurial/configitems.py	Fri Jan 18 16:03:37 2019 +0100
@@ -556,6 +556,9 @@
 coreconfigitem('experimental', 'mergetempdirprefix',
     default=None,
 )
+coreconfigitem('experimental', 'mmapindexthreshold',
+    default=None,
+)
 coreconfigitem('experimental', 'narrow',
     default=False,
 )
@@ -987,10 +990,6 @@
 coreconfigitem('push', 'pushvars.server',
     default=False,
 )
-coreconfigitem('storage', 'mmap-threshold',
-    default=None,
-    alias=[('experimental', 'mmapindexthreshold')],
-)
 coreconfigitem('rewrite', 'backup-bundle',
     default=True,
     alias=[('ui', 'history-editing-backup')],

--- a/mercurial/localrepo.py	Fri Jan 18 16:02:26 2019 +0100
+++ b/mercurial/localrepo.py	Fri Jan 18 16:03:37 2019 +0100
@@ -758,7 +758,8 @@
     if 0 <= chainspan:
         options[b'maxdeltachainspan'] = chainspan
 
-    mmapindexthreshold = ui.configbytes(b'storage', b'mmap-threshold')
+    mmapindexthreshold = ui.configbytes(b'experimental',
+                                        b'mmapindexthreshold')
     if mmapindexthreshold is not None:
         options[b'mmapindexthreshold'] = mmapindexthreshold