fix 'hg <not-log> -v --template foo' with revisions without copies

mercurial/cmdutil.py

@@ -224,7 +224,7 class changeset_printer(object):
             return 1
         return 0
 
-    def show(self, rev=0, changenode=None, copies=None, **props):
+    def show(self, rev=0, changenode=None, copies=(), **props):
         if self.buffered:
             self.ui.pushbuffer()
             self._show(rev, changenode, copies, props)

tests/test-command-template

@@ -39,6 +39,9 hg log --debug > log.out
 hg log --debug --style default > style.out
 diff log.out style.out
 
+echo '# revision with no copies (used to print a traceback)'
+hg tip -v --template '\n'
+
 echo '# compact style works'
 hg log --style compact
 hg log -v --style compact

tests/test-command-template.out

@@ -2,6 +2,8
 #  normal
 #  verbose
 #  debug
+# revision with no copies (used to print a traceback)
+
 # compact style works
 4[tip]   32a18f097fcc   1970-01-17 04:53 +0000   person
   new branch