showconfig: show source file and line with --debug

mercurial/commands.py

@@ -797,10 +797,16 b' def showconfig(ui, repo, *values, **opts'
         if values:
             for v in values:
                 if v == section:
+                    ui.debug('%s: ' %
+                             ui.configsource(section, name, untrusted))
                     ui.write('%s=%s\n' % (sectname, value))
                 elif v == sectname:
+                    ui.debug('%s: ' %
+                             ui.configsource(section, name, untrusted))
                     ui.write(value, '\n')
         else:
+            ui.debug('%s: ' %
+                     ui.configsource(section, name, untrusted))
             ui.write('%s=%s\n' % (sectname, value))
 
 def debugsetparents(ui, repo, rev1, rev2=None):

mercurial/ui.py

@@ -151,6 +151,9 b' class ui(object):'
             return self.ucdata
         return self.cdata
 
+    def configsource(self, section, name, untrusted=False):
+        return self._get_cdata(untrusted).getsource(section, name) or 'none'
+
     def config(self, section, name, default=None, untrusted=False):
         value = self._get_cdata(untrusted).get(section, name, default)
         if self.debugflag and not untrusted: