subrepo: use safehasattr instead of hasattr

Some of these instances could be rewritten as clever getattr(x, y,
default) ladders, but that felt like it impeded readability too much
to be worth the modest efficiency gain.

mercurial/subrepo.py

@@ -181,22 +181,22 b' def _updateprompt(ui, sub, dirty, local,'
 def reporelpath(repo):
     """return path to this (sub)repo as seen from outermost repo"""
     parent = repo
-    while hasattr(parent, '_subparent'):
+    while util.safehasattr(parent, '_subparent'):
         parent = parent._subparent
     return repo.root[len(parent.root)+1:]
 
 def subrelpath(sub):
     """return path to this subrepo as seen from outermost repo"""
-    if hasattr(sub, '_relpath'):
+    if util.safehasattr(sub, '_relpath'):
         return sub._relpath
-    if not hasattr(sub, '_repo'):
+    if not util.safehasattr(sub, '_repo'):
         return sub._path
     return reporelpath(sub._repo)
 
 def _abssource(repo, push=False, abort=True):
     """return pull/push path of repo - either based on parent repo .hgsub info
     or on the top repo config. Abort or return None if no source found."""
-    if hasattr(repo, '_subparent'):
+    if util.safehasattr(repo, '_subparent'):
         source = util.url(repo._subsource)
         if source.isabs():
             return str(source)
@@ -208,7 +208,7 b' def _abssource(repo, push=False, abort=T'
             parent.path = posixpath.normpath(parent.path)
             return str(parent)
     else: # recursion reached top repo
-        if hasattr(repo, '_subtoppath'):
+        if util.safehasattr(repo, '_subtoppath'):
             return repo._subtoppath
         if push and repo.ui.config('paths', 'default-push'):
             return repo.ui.config('paths', 'default-push')