graphlog: style with header and footer (issue2395)

The glog command didn't emit header and footer from the style, as demonstrated
by "hg glog --style xml". Asciiart combined with xml markup hardly makes sense,
but header and footer might however be useful for adding for example html pre
tags around the graph.

hgext/graphlog.py

@@ -229,7 +229,9 b' def generate(ui, dag, displayer, showpar'
         char = ctx.node() in showparents and '@' or 'o'
         displayer.show(ctx)
         lines = displayer.hunk.pop(rev).split('\n')[:-1]
+        displayer.flush(rev)
         ascii(ui, state, type, char, lines, edgefn(seen, rev, parents))
+    displayer.close()
 
 def graphlog(ui, repo, path=None, **opts):
     """show revision history alongside an ASCII revision graph

tests/test-glog.t

@@ -740,6 +740,17 b' Issue1896: File log with explicit style'
      date:        Thu Jan 01 00:00:00 1970 +0000
      summary:     one
   
+Issue2395: glog --style header and footer
+  $ hg glog --style=xml one
+  <?xml version="1.0"?>
+  <log>
+  o  <logentry revision="0" node="3d578b4a1f537d5fcf7301bfa9c0b97adfaa6fb1">
+     <author email="test">test</author>
+     <date>1970-01-01T00:00:00+00:00</date>
+     <msg xml:space="preserve">one</msg>
+     </logentry>
+  </log>
+
   $ cd ..
 
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