tests/test-changelog-exec.out

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.

% manifest of p2:
bar
foo

created new head
% manifest of p1:
foo
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
% this should not mention bar:
changeset:   3:ef2fc9b4a51b
tag:         tip
parent:      2:ed1b79f46b9a
parent:      1:d394a8db219b
user:        test
date:        Thu Jan 01 00:00:00 1970 +0000
description:
merge


   rev    offset  length   base linkrev nodeid       p1           p2
     0         0       5      0       1 b004912a8510 000000000000 000000000000