fix(mercurial): fixed issue with rebase logic after bump to mercurial 6.3

the previous spec expected just a single base. Now this needs to be a list of items

fixes  #5704

vcsserver/remote/hg_remote.py

@@ -1125,6 +1125,7 b' class HgRemote(RemoteBase):'
 
     @reraise_safe_exceptions
     def rebase(self, wire, source='', dest='', abort=False):
+
         repo = self._factory.repo(wire)
         baseui = self._factory._create_config(wire['config'])
         repo.ui.setconfig(b'ui', b'merge', b'internal:dump')
@@ -1134,8 +1135,19 b' class HgRemote(RemoteBase):'
         # used but instead uses a default value.
         repo.ui.setconfig(b'ui', b'interactive', False)
 
-        rebase.rebase(baseui, repo, base=safe_bytes(source or ''), dest=safe_bytes(dest or ''),
-                      abort=abort, keep=not abort)
+        rebase_kws = dict(
+            keep=not abort,
+            abort=abort
+        )
+
+        if source:
+            source = repo[source]
+            rebase_kws['base'] = [source.hex()]
+        if dest:
+            dest = repo[dest]
+            rebase_kws['dest'] = dest.hex()
+
+        rebase.rebase(baseui, repo, **rebase_kws)
 
     @reraise_safe_exceptions
     def tag(self, wire, name, revision, message, local, user, tag_time, tag_timezone):