repo-config: adjust "root" path for parsing shared config

That "root" argument is used to resolve relative path in the config. For a
repository config it is expected to be the root of the working copy (the
directory that contains the `.hg` directory). Before this patch, the config was
loaded using the `.hg/` directory of the share source, this is not the right
directory and would break in all cases.

Instead we use the working copy directory of the share. This is not always
good, if some relative path we pointing inside the source's `.hg`. However that
is better than something plain wrong. Also this is the right answer for all
path that refer to the actual working copy.

Fixing this ambiguity is left as an exercises to a future developer. At least we no longer use a plain invalid value.

mercurial/dispatch.py

@@ -947,8 +947,7 def _readsharedsourceconfig(ui, path):
                 return
             hgvfs = vfs.vfs(os.path.join(path, b".hg"))
             sharedvfs = localrepo._getsharedvfs(hgvfs, requirements)
-            root = sharedvfs.base
-            ui.readconfig(sharedvfs.join(b"hgrc"), root)
+            ui.readconfig(sharedvfs.join(b"hgrc"), root=path)
     except IOError:
         pass