changegroup: rename "dh" to the clearer "deltaheads" We have a lot of frequently used abbreviations, but this is not one of them.

changegroup: rename "srccontent" to "cgnodes" It's the list of nodes in the incoming changegroup, so "cgnodes" made more sense to me.

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.

revlog: delete obsolete comment The comment seems to refer to code that was deleted in 557988c691d1 (revlog.addgroup(): always use _addrevision() to add new revlog entries, 2010-10-08).