largefiles: don't crash when cloning to a remote repo

The immediate crash was when checking for requirements immediately after this,
but lfcommands.downloadlfiles() will also crash if --all-largefiles is
specified.  That has been in place since atleast 5884812686f7 (2.3-rc) without
anyone noticing.

I can't tell from the peer classes if there's a way to make the custom largefile
functionality work in this case, but atleast it doesn't crash.

hgext/largefiles/overrides.py

@@ -838,6 +838,12 b' def hgclone(orig, ui, opts, *args, **kwa'
         sourcerepo, destrepo = result
         repo = destrepo.local()
 
+        # When cloning to a remote repo (like through SSH), no repo is available
+        # from the peer.   Therefore the largefiles can't be downloaded and the
+        # hgrc can't be updated.
+        if not repo:
+            return result
+
         # If largefiles is required for this repo, permanently enable it locally
         if 'largefiles' in repo.requirements:
             fp = repo.vfs('hgrc', 'a', text=True)

tests/test-init.t

@@ -111,6 +111,14 b' clone to remote1'
   remote: adding file changes
   remote: added 1 changesets with 1 changes to 1 files
 
+The largefiles extension doesn't crash
+  $ hg clone -e "python \"$TESTDIR/dummyssh\"" local ssh://user@dummy/remotelf --config extensions.largefiles=
+  searching for changes
+  remote: adding changesets
+  remote: adding manifests
+  remote: adding file changes
+  remote: added 1 changesets with 1 changes to 1 files
+
 init to existing repo
 
   $ hg init -e "python \"$TESTDIR/dummyssh\"" ssh://user@dummy/remote1
@@ -133,6 +141,8 b' output of dummyssh'
   Got arguments 1:user@dummy 2:hg -R remote2 serve --stdio
   Got arguments 1:user@dummy 2:hg init remote1
   Got arguments 1:user@dummy 2:hg -R remote1 serve --stdio
+  Got arguments 1:user@dummy 2:hg init remotelf
+  Got arguments 1:user@dummy 2:hg -R remotelf serve --stdio
   Got arguments 1:user@dummy 2:hg init remote1
   Got arguments 1:user@dummy 2:hg init remote1