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.

changegroup: use a copy of hookargs when invoking the changegroup hook addchangegroup creates a runhook function that is used to invoke the changegroup and incoming hooks, but at the time the function is called, the contents of hookargs associated with the transaction may have been modified externally. For instance, bundle2 code affects it with obsolescence markers and bookmarks info. It also creates problems when a single transaction is used with multiple changegroups added (as per an upcoming change), whereby the contents of hookargs are that of after adding a latter changegroup when invoking the hook for the first changegroup.

tests: pull common http server setup out of individual tests There are currently two different tests using roughly the same code to create temporary scripts acting as HTTP servers. As there is going to be at least one more in an upcoming change, factor those out in a standalone dumbhttp.py script.

util: move md5 back next to sha1 and allow to call it without an argument This effectively backs out changeset 908c5906091b. The API change is done so that both util.sha1 and util.md5 can be called the same way. The function is moved in order to use it for md5 checksumming for an upcoming bundle2 feature.

test-bundle2-exchange: do not drop HG_NODE from the hook output HG_NODE is precisely something we would like to test.

obsolete: update test-commit-amend to use obsolete option This test actually used the obs.py file as part of the test, so we need to fix up the test a little more than usual to work with the new obsolete option flags.