extensions: use ismoduleinternal() thoroughly

"ships-with-hg-core" would be long enough to typo.

mercurial/commands.py

@@ -2394,9 +2394,10 b' def debugextensions(ui, **opts):'
     hgver = util.version()
     fm = ui.formatter('debugextensions', opts)
     for extname, extmod in sorted(exts, key=operator.itemgetter(0)):
+        isinternal = extensions.ismoduleinternal(extmod)
         extsource = extmod.__file__
         exttestedwith = getattr(extmod, 'testedwith', '').split()
-        if exttestedwith == ['ships-with-hg-core']:
+        if isinternal:
             showtestedwith = ['internal']
         else:
             showtestedwith = exttestedwith
@@ -2410,8 +2411,7 b' def debugextensions(ui, **opts):'
             fm.write('name', '%s', extname)
             if not exttestedwith:
                 fm.plain(_(' (untested!)\n'))
-            elif (exttestedwith == ['ships-with-hg-core']
-                  or hgver in exttestedwith):
+            elif isinternal or hgver in exttestedwith:
                 fm.plain('\n')
             else:
                 lasttestedversion = exttestedwith[-1]

mercurial/dispatch.py

@@ -929,7 +929,7 b' def _exceptionwarning(ui):'
                 break
 
             # Never blame on extensions bundled with Mercurial.
-            if testedwith == 'ships-with-hg-core':
+            if extensions.ismoduleinternal(mod):
                 continue
 
             tested = [util.versiontuple(t, 2) for t in testedwith.split()]