error: add a new UnknownIdentifier error type This will be used by the revset and fileset code to communicate more specific errors to higher levels so that we might be able to offer suggestions about what function might have been similar.

log: display closing-branch nodes as "_" (BC) In plain `hg log` there is no indication that a commit closes a branch. You can use hg log --debug, but this is too verbose. A simple idea copied from thg and other graphical viewers is to display the node for a closing-branch commit as a horizontal line. I think this technically is a BC if we consider the graphlog to be part of the stdout API, but I really can't imagine who the hell is parsing the graphlog to determine information about commits.

manifest: move pure parsing code out of pure This lets us transition more smoothly.

manifest.c: new extension code to lazily parse manifests This lets us iterate manifests in order, but do a _lot_ less work in the common case when we only care about a few manifest entries. Many thanks to Mike Edgar for reviewing this in advance of it going out to the list, which caught many things I missed. This version of the patch includes C89 fixes from Sean Farley and many correctness/efficiency cleanups from Martin von Zweigbergk. Thanks to both!