cmdutil: changeset_printer: use methods of filectx/changectx.

This allows extensions that modify changeset metadata (e.g.
description) by overriding methods of changectx to get consistent
behavior from all log-like commands, regardless of whether templates
or styles are used. Without this, overriding changectx methods works
if you use styles or templates, but not with default log format.

This meant adding filectx.extra() for consistency with changectx.

mercurial/cmdutil.py

@@ -652,9 +652,8 b' class changeset_printer(object):'
             return
 
         log = self.repo.changelog
-        changes = log.read(changenode)
-        date = util.datestr(changes[2])
-        extra = changes[5]
+        date = util.datestr(ctx.date())
+        extra = ctx.extra()
         branch = extra.get("branch")
 
         hexfunc = self.ui.debugflag and hex or short
@@ -674,9 +673,10 b' class changeset_printer(object):'
             self.ui.write(_("parent:      %d:%s\n") % parent)
 
         if self.ui.debugflag:
+            mnode = ctx.manifestnode()
             self.ui.write(_("manifest:    %d:%s\n") %
-                          (self.repo.manifest.rev(changes[0]), hex(changes[0])))
-        self.ui.write(_("user:        %s\n") % changes[1])
+                          (self.repo.manifest.rev(mnode), hex(mnode)))
+        self.ui.write(_("user:        %s\n") % ctx.user())
         self.ui.write(_("date:        %s\n") % date)
 
         if self.ui.debugflag:
@@ -685,8 +685,8 b' class changeset_printer(object):'
                                   files):
                 if value:
                     self.ui.write("%-12s %s\n" % (key, " ".join(value)))
-        elif changes[3] and self.ui.verbose:
-            self.ui.write(_("files:       %s\n") % " ".join(changes[3]))
+        elif ctx.files() and self.ui.verbose:
+            self.ui.write(_("files:       %s\n") % " ".join(ctx.files()))
         if copies and self.ui.verbose:
             copies = ['%s (%s)' % c for c in copies]
             self.ui.write(_("copies:      %s\n") % ' '.join(copies))
@@ -696,7 +696,7 b' class changeset_printer(object):'
                 self.ui.write(_("extra:       %s=%s\n")
                               % (key, value.encode('string_escape')))
 
-        description = changes[4].strip()
+        description = ctx.description().strip()
         if description:
             if self.ui.verbose:
                 self.ui.write(_("description:\n"))

mercurial/context.py

@@ -299,6 +299,7 b' class filectx(object):'
     def files(self): return self._changectx.files()
     def description(self): return self._changectx.description()
     def branch(self): return self._changectx.branch()
+    def extra(self): return self._changectx.extra()
     def manifest(self): return self._changectx.manifest()
     def changectx(self): return self._changectx