commands: support creating stream clone bundles Now that we have support for recognizing the streaming clone bundle type, add a debug command for creating them. I decided to create a new debug command instead of adding support to `hg bundle` because stream clone bundles are not exactly used the same way as normal bundle files and I don't want to commit to supporting them through the official `hg bundle` command forever. A debug command, however, can be changed without as much concern for backwards compatibility. As part of this, `hg bundle` will explicitly reject requests to produce stream bundles. This command will be required by server operators using stream clone bundles with the clone bundles feature.

exchange: support for streaming clone bundles Now that we have a mechanism to produce and consume streaming clone bundles, we need to teach the human-facing bundle specification parser and the internal bundle file header reading code to be aware of this new format. This patch does so. For the human-facing bundle specification, we choose the name "packed" to describe "streaming clone bundles" because the bundle is essentially a "pack" of raw revlog files that are "packed" together. There should probably be a bikeshed over the name, especially since it is human facing.

streamclone: support for producing and consuming stream clone bundles Up to this point, stream clones only existed as a dynamically generated data format produced and consumed during streaming clones. In order to support this efficient cloning format with the clone bundles feature, we need a more formal, on disk representation of the streaming clone data. This patch introduces a new "bundle" type for streaming clones. Unlike existing bundles, it does not contain changegroup data. It does, however, share the same concepts like the 4 byte header which identifies the type of data that follows and the 2 byte abbreviation for compression types (of which only "UN" is currently supported). The new bundle format is essentially the existing stream clone version 1 data format with some headers at the beginning. Content negotiation at stream clone request time checked for repository format/requirements compatibility before initiating a stream clone. We can't do active content negotiation when using clone bundles. So, we put this set of requirements inside the payload so consumers have a built-in mechanism for checking compatibility before reading and applying lots of data. Of course, we will also advertise this requirements set in clone bundles. But that's for another patch. We currently don't have a mechanism to produce and consume this new bundle format. This will be implemented in upcoming patches. It's worth noting that if a legacy client attempts to `hg unbundle` a stream clone bundle (with the "HGS1" header), it will abort with: "unknown bundle version S1," which seems appropriate.

spelling: fix typo in transaction error messages

transaction: reorder unlinking .hg/journal and .hg/journal.backupfiles After this reordering, absence of '.hg/journal' just before starting new transaction means also absence of '.hg/journal.backupfiles'. In this case, all temporary files for preceding transaction should be completely unlinked, and HG_PENDING doesn't cause unintentional reading stalled temporary files in. Otherwise, 'repo.transaction()' raises exception with "run 'hg recover' to clean up transaction" hint.

merge: make in-memory changes visible to external update hooks 51844b8b5017 (while 3.4 code-freeze) made all 'update' hooks run after releasing wlock for visibility of in-memory dirstate changes. But this breaks paired invocation of 'preupdate' and 'update' hooks. For example, 'hg backout --merge' for TARGET revision, which isn't parent of CURRENT, consists of steps below: 1. update from CURRENT to TARGET 2. commit BACKOUT revision, which backs TARGET out 3. update from BACKOUT to CURRENT 4. merge TARGET into CURRENT Then, we expects hooks to run in the order below: - 'preupdate' on CURRENT for (1) - 'update' on TARGET for (1) - 'preupdate' on BACKOUT for (3) - 'update' on CURRENT for (3) - 'preupdate' on TARGET for (4) - 'update' on CURRENT/TARGET for (4) But hooks actually run in the order below: - 'preupdate' on CURRENT for (1) - 'preupdate' on BACKOUT for (3) - 'preupdate' on TARGET for (4) - 'update' on TARGET for (1), but actually on CURRENT/TARGET - 'update' on CURRENT for (3), but actually on CURRENT/TARGET - 'update' on CURRENT for (4), but actually on CURRENT/TARGET Root cause of the issue focused by 51844b8b5017 is that external 'update' hook process can't view in-memory changes (especially, of dirstate), because they aren't written out until the end of transaction (or wlock). Now, hooks can be invoked just after updating, because previous patches made in-memory changes visible to external process. This patch may break backward compatibility from the point of view of "scheduling hook execution", but should be reasonable because 'update' hooks had been executed in this order before 3.4. This patch tests "hg backout" and "hg unshelve", because the former activates the transaction before 'update' hook invocation, but the former doesn't.