--- a/mercurial/debugcommands.py	Fri Feb 18 12:55:39 2022 +0100
+++ b/mercurial/debugcommands.py	Fri Feb 18 14:27:43 2022 +0100
@@ -91,7 +91,6 @@
     vfs as vfsmod,
     wireprotoframing,
     wireprotoserver,
-    wireprotov2peer,
 )
 from .interfaces import repository
 from .utils import (
@@ -179,6 +178,12 @@
             _(b'add single file all revs overwrite'),
         ),
         (b'n', b'new-file', None, _(b'add new file at each rev')),
+        (
+            b'',
+            b'from-existing',
+            None,
+            _(b'continue from a non-empty repository'),
+        ),
     ],
     _(b'[OPTION]... [TEXT]'),
 )
@@ -189,6 +194,7 @@
     mergeable_file=False,
     overwritten_file=False,
     new_file=False,
+    from_existing=False,
 ):
     """builds a repo with a given DAG from scratch in the current empty repo
 
@@ -227,7 +233,7 @@
         text = ui.fin.read()
 
     cl = repo.changelog
-    if len(cl) > 0:
+    if len(cl) > 0 and not from_existing:
         raise error.Abort(_(b'repository is not empty'))
 
     # determine number of revs in DAG
@@ -273,7 +279,10 @@
                             x[fn].data() for x in (pa, p1, p2)
                         ]
                         m3 = simplemerge.Merge3Text(base, local, other)
-                        ml = [l.strip() for l in m3.merge_lines()]
+                        ml = [
+                            l.strip()
+                            for l in simplemerge.render_minimized(m3)[0]
+                        ]
                         ml.append(b"")
                     elif at > 0:
                         ml = p1[fn].data().split(b"\n")
@@ -4352,8 +4361,8 @@
 
     ``--peer`` can be used to bypass the handshake protocol and construct a
     peer instance using the specified class type. Valid values are ``raw``,
-    ``http2``, ``ssh1``, and ``ssh2``. ``raw`` instances only allow sending
-    raw data payloads and don't support higher-level command actions.
+    ``ssh1``. ``raw`` instances only allow sending raw data payloads and
+    don't support higher-level command actions.
 
     ``--noreadstderr`` can be used to disable automatic reading from stderr
     of the peer (for SSH connections only). Disabling automatic reading of
@@ -4528,13 +4537,11 @@
 
     if opts[b'peer'] and opts[b'peer'] not in (
         b'raw',
-        b'http2',
         b'ssh1',
-        b'ssh2',
     ):
         raise error.Abort(
             _(b'invalid value for --peer'),
-            hint=_(b'valid values are "raw", "ssh1", and "ssh2"'),
+            hint=_(b'valid values are "raw" and "ssh1"'),
         )
 
     if path and opts[b'localssh']:
@@ -4602,18 +4609,6 @@
                 None,
                 autoreadstderr=autoreadstderr,
             )
-        elif opts[b'peer'] == b'ssh2':
-            ui.write(_(b'creating ssh peer for wire protocol version 2\n'))
-            peer = sshpeer.sshv2peer(
-                ui,
-                url,
-                proc,
-                stdin,
-                stdout,
-                stderr,
-                None,
-                autoreadstderr=autoreadstderr,
-            )
         elif opts[b'peer'] == b'raw':
             ui.write(_(b'using raw connection to peer\n'))
             peer = None
@@ -4666,34 +4661,7 @@
 
         opener = urlmod.opener(ui, authinfo, **openerargs)
 
-        if opts[b'peer'] == b'http2':
-            ui.write(_(b'creating http peer for wire protocol version 2\n'))
-            # We go through makepeer() because we need an API descriptor for
-            # the peer instance to be useful.
-            maybe_silent = (
-                ui.silent()
-                if opts[b'nologhandshake']
-                else util.nullcontextmanager()
-            )
-            with maybe_silent, ui.configoverride(
-                {(b'experimental', b'httppeer.advertise-v2'): True}
-            ):
-                peer = httppeer.makepeer(ui, path, opener=opener)
-
-            if not isinstance(peer, httppeer.httpv2peer):
-                raise error.Abort(
-                    _(
-                        b'could not instantiate HTTP peer for '
-                        b'wire protocol version 2'
-                    ),
-                    hint=_(
-                        b'the server may not have the feature '
-                        b'enabled or is not allowing this '
-                        b'client version'
-                    ),
-                )
-
-        elif opts[b'peer'] == b'raw':
+        if opts[b'peer'] == b'raw':
             ui.write(_(b'using raw connection to peer\n'))
             peer = None
         elif opts[b'peer']:
@@ -4774,17 +4742,10 @@
                 with peer.commandexecutor() as e:
                     res = e.callcommand(command, args).result()
 
-                if isinstance(res, wireprotov2peer.commandresponse):
-                    val = res.objects()
-                    ui.status(
-                        _(b'response: %s\n')
-                        % stringutil.pprint(val, bprefix=True, indent=2)
-                    )
-                else:
-                    ui.status(
-                        _(b'response: %s\n')
-                        % stringutil.pprint(res, bprefix=True, indent=2)
-                    )
+                ui.status(
+                    _(b'response: %s\n')
+                    % stringutil.pprint(res, bprefix=True, indent=2)
+                )
 
         elif action == b'batchbegin':
             if batchedcommands is not None: