diff --git a/mercurial/changegroup.py b/mercurial/changegroup.py
--- a/mercurial/changegroup.py
+++ b/mercurial/changegroup.py
@@ -697,9 +697,16 @@ def deltagroup(repo, store, nodes, ischa
         progress = repo.ui.makeprogress(topic, unit=_('chunks'),
                                         total=len(nodes))
 
+    configtarget = repo.ui.config('devel', 'bundle.delta')
+    if configtarget not in ('', 'p1'):
+        msg = _("""config "devel.bundle.delta" as unknown value: %s""")
+        repo.ui.warn(msg % configtarget)
+
     deltamode = repository.CG_DELTAMODE_STD
     if forcedeltaparentprev:
         deltamode = repository.CG_DELTAMODE_PREV
+    elif configtarget == 'p1':
+        deltamode = repository.CG_DELTAMODE_P1
 
     revisions = store.emitrevisions(
         nodes,
diff --git a/mercurial/configitems.py b/mercurial/configitems.py
--- a/mercurial/configitems.py
+++ b/mercurial/configitems.py
@@ -329,6 +329,9 @@ coreconfigitem('devel', 'all-warnings',
 coreconfigitem('devel', 'bundle2.debug',
     default=False,
 )
+coreconfigitem('devel', 'bundle.delta',
+    default='',
+)
 coreconfigitem('devel', 'cache-vfs',
     default=None,
 )
diff --git a/mercurial/repository.py b/mercurial/repository.py
--- a/mercurial/repository.py
+++ b/mercurial/repository.py
@@ -42,6 +42,7 @@ REVISION_FLAGS_KNOWN = (
 CG_DELTAMODE_STD = b'default'
 CG_DELTAMODE_PREV = b'previous'
 CG_DELTAMODE_FULL = b'fulltext'
+CG_DELTAMODE_P1 = b'p1'
 
 class ipeerconnection(interfaceutil.Interface):
     """Represents a "connection" to a repository.
diff --git a/mercurial/utils/storageutil.py b/mercurial/utils/storageutil.py
--- a/mercurial/utils/storageutil.py
+++ b/mercurial/utils/storageutil.py
@@ -373,6 +373,9 @@ def emitrevisions(store, nodes, nodesord
         # We're instructed to send fulltext. Honor that.
         elif deltamode == repository.CG_DELTAMODE_FULL:
             baserev = nullrev
+        # We're instructed to use p1. Honor that
+        elif deltamode == repository.CG_DELTAMODE_P1:
+            baserev = p1rev
 
         # There is a delta in storage. We try to use that because it
         # amounts to effectively copying data from storage and is
diff --git a/tests/test-bundle.t b/tests/test-bundle.t
--- a/tests/test-bundle.t
+++ b/tests/test-bundle.t
@@ -900,3 +900,8 @@ the warning shouldn't be emitted
   $ hg update -R ../update2bundled.hg -r 0
   0 files updated, 0 files merged, 2 files removed, 0 files unresolved
 #endif
+
+Test the option that create slim bundle
+
+  $ hg bundle -a --config devel.bundle.delta=p1 ./slim.hg
+  3 changesets found