manifest: repurpose flagsdiff() into (node-and-flag)diff() The manifestdict class already has a method for diff flags between two manifests (presumably because there is no full access to the private _flags field). The only caller is merge.manifestmerge(), which also wants a diff of files between the same manifests. Let's combine the code for diffing files and flags into a single method on manifestdict. This puts all the manifest diffing in one place and will allow for further simplification. It might also be useful for it to be encapsulated in manifestdict if we later decide to to shard manifests. The docstring is intentionally unclear about missing entries for now.

util: add a file handle wrapper class that does hash digest validation It is going to be used for the remote-changegroup feature in bundle2.

util: add a helper class to compute digests It is going to be used for the remote-changegroup feature in bundle2.

bundle2: merge return values when bundle contains multiple changegroups A bundle2 may contain multiple parts adding changegroups, in which case there are multiple operation records for changegroups, each with its own return value. Those multiple return values are aggregated in a single cgresult value for the whole operation. As can be seen in the associated test case, the situation with hooks is not really the best, but without deeper thoughts and changes, we can't do much better. Hopefully, things will be improved before bundle2 is enabled by default. In the meanwhile, multiple changegroups is not expected to be in widespread use, and even less expected to be used for pushes. Also, not many clients cloning or pulling bundle2 with multiple changesets are not expected to have changegroup hooks anyways.