revlog: rename list of nodes from "content" to "nodes"

revlog: rename list of nodes from "content" to "nodes"

It seems like the reason for "content" is that the variable contains
the nodes that the changegroup "contains", see e234eda20984 (revlog:
make addgroup returns a list of node contained in the added source,
2012-01-13), but "nodes" seems much clearer.

--- a/mercurial/revlog.py	Thu Jun 15 13:25:41 2017 -0700
+++ b/mercurial/revlog.py	Thu Jun 15 13:42:35 2017 -0700
@@ -1854,7 +1854,7 @@
         this revlog and the node that was added.
         """
 
-        content = []
+        nodes = []
 
         r = len(self)
         end = 0
@@ -1885,7 +1885,7 @@
                 delta = chunkdata['delta']
                 flags = chunkdata['flags'] or REVIDX_DEFAULT_FLAGS
 
-                content.append(node)
+                nodes.append(node)
 
                 link = linkmapper(cs)
                 if node in self.nodemap:
@@ -1944,7 +1944,7 @@
                 dfh.close()
             ifh.close()
 
-        return content
+        return nodes
 
     def iscensored(self, rev):
         """Check if a file revision is censored."""