bundlerepo: handle changegroup induced phase movement in the associated method

These movement comes from handling the changegroup part, so we keeps the code
grouped. This will be important when handling more part (and more changegroup
part in the future)

This induce a small code duplication, but it does not looks terrible.

mercurial/bundlerepo.py

@@ -327,6 +327,14 b' class bundlerepository:'
                 _(b'bundle type %s cannot be read') % type(bundle)
             )
 
+    def _handle_bundle1(self, bundle, bundlepath):
+        if bundle.compressed():
+            f = self._writetempbundle(bundle.read, b'.hg10un', header=b'HG10UN')
+            bundle = exchange.readbundle(self.ui, f, bundlepath, self.vfs)
+
+        self._bundlefile = bundle
+        self._cgunpacker = bundle
+
         self.firstnewrev = self.changelog.repotiprev + 1
         phases.retractboundary(
             self,
@@ -335,14 +343,6 b' class bundlerepository:'
             [ctx.node() for ctx in self[self.firstnewrev :]],
         )
 
-    def _handle_bundle1(self, bundle, bundlepath):
-        if bundle.compressed():
-            f = self._writetempbundle(bundle.read, b'.hg10un', header=b'HG10UN')
-            bundle = exchange.readbundle(self.ui, f, bundlepath, self.vfs)
-
-        self._bundlefile = bundle
-        self._cgunpacker = bundle
-
     def _handle_bundle2_cg_part(self, bundle, part):
         assert part.type == b'changegroup'
         cgstream = part
@@ -356,6 +356,14 b' class bundlerepository:'
 
         self._cgunpacker = changegroup.getunbundler(version, cgstream, b'UN')
 
+        self.firstnewrev = self.changelog.repotiprev + 1
+        phases.retractboundary(
+            self,
+            None,
+            phases.draft,
+            [ctx.node() for ctx in self[self.firstnewrev :]],
+        )
+
     def _writetempbundle(self, readfn, suffix, header=b''):
         """Write a temporary file to disk"""
         fdtemp, temp = self.vfs.mkstemp(prefix=b"hg-bundle-", suffix=suffix)