dispatch: pass root path in ui.readconfig() as root of main repo

Since we are reading main (shared-source) repository config options, we
should pass root as that repository root only.

Differential Revision: https://phab.mercurial-scm.org/D9359

mercurial/dispatch.py

@@ -919,7 +919,8 b' def _readsharedsourceconfig(ui, path):'
                 return
             hgvfs = vfs.vfs(os.path.join(path, b".hg"))
             sharedvfs = localrepo._getsharedvfs(hgvfs, requirements)
-            ui.readconfig(sharedvfs.join(b"hgrc"), path)
+            root = sharedvfs.base
+            ui.readconfig(sharedvfs.join(b"hgrc"), root)
     except IOError:
         pass