Mercurial: Changelog

exchangev2: support fetching shallow files history This commit teaches the exchangev2 client code to handle fetching shallow files data. Only shallow fetching of files data is supported: shallow fetching of changeset and manifest data is explicitly not yet supported. Previously, we would fetch file revisions for changesets that were received by the current pull operation. In the new model, we calculate the set of "relevant" changesets given the pull depth and only fetch files data for those changesets. We also teach the "filesdata" command invocation to vary parameters as needed. The implementation here is far from complete or optimal. Subsequent pulls will end up re-fetching a lot of files data. But the application of this data should mostly be a no-op on the client, so it isn't a big deal. Depending on the order file revisions are fetched in, revisions could get inserted with the wrong revision number relationships. I think the best way to deal with this is to remove revision numbers from storage and to either dynamically derive them (by reconstructing a DAG from nodes/parents) or remove revision numbers from the file storage interface completely. A missing API that we'll likely want to write pretty soon is "ensure files for revision(s) are present." We can kind of cajole exchangev2.pull() to do this. But it isn't very efficient. For example, in simple cases like widening the store to obtain data for a single revision, it is probably more efficient to walk the manifest and find exactly which file revisions are missing and to make explicit requests for just their data. In more advanced cases, asking the server for all files data may be more efficient, even though it requires sending data the client already has. There is tons of room for future experimentation here. And TBH I'm not sure what the final state will be. Anyway, this commit gets us pretty close to being able to have shallow and narrow checkouts with exchangev2/sqlite storage. Close enough that a minimal extension should be able to provide fill in the gaps until the code in core stabilizes and there is a user-facing way to trigger the narrow/shallow bits from `hg clone` without also implying using of the narrow extension... Differential Revision: https://phab.mercurial-scm.org/D5169

sqlitestore: support for storing revisions without their parents This commit kinda/sorta implements the equivalent of ellipsis nodes for the SQLite storage backend. Without implementing full blown ellipsis nodes (and the necessary support for them in the wire protocol), we instead teach the store to rewrite the p1 and p2 nodes to nullid when the incoming parent isn't in the local store. This allows servers to remain dumb and send the real parent and have the clients deal with the missing parent problem. This obviously isn't ideal because a benefit of ellipsis nodes is we can insert a fake parent to ellide missing changesets. But neither solution is ideal because it drops the original parent from storage. We could probably teach the SQLite store to retain the original parent and handle missing parents at read time. However, parent revisions are stored as integers and it isn't trivial to store an "empty" revision in the store yet, which would be necessary to represent the "missing" parent. The store is somewhat intelligent in trying to remove the missing parents metadata when the revision is re-added. But, revision numbers will be all messed up in that case, so I'm not sure it is worth it. At some point we'll likely want to remove the concept of revision numbers from the database and have the store invent them at index generation time. Or even better, we can do away with revision numbers from the file storage interface completely. We'll get there eventually... Differential Revision: https://phab.mercurial-scm.org/D5168

wireprotov2: support exposing linknode of file revisions When supporting shallow file storage, clients may fetch file revisions by changeset. But they may not readily know which changeset introduced a specific file revision. The "linknode" is used to record which changeset introduces which file revision. This commit teaches the "filedata" and "filesdata" wire protocol commands to expose the linknode for file revisions. The implementation is likely wrong when hidden changesets are in play, since the linknode may refer to a hidden changeset. We can deal with this problem later. Differential Revision: https://phab.mercurial-scm.org/D5167

localrepo: support marking repos as having shallow file storage Various operations against repositories need to know if repository storage is full or partial. For example, a checkout (including possibly a widening of a sparse checkout), needs to know if it can assume all file revisions are available or whether to look for missing revisions first. This commit lays the plumbing for doing that. We define a repo creation option that indicates that shallow file storage is desired. The SQLite store uses this creation option to add an extra repo requirement indicating file storage is shallow. A new repository feature has been added to indicate that file storage is shallow. The SQLite store adds this feature when the shallow file store requirement is present. Code can now look at repo.features to determine if repo file storage may be shallow and take additional actions if so. While we're here, we also teach the SQLite store to handle the narrow repo requirement, which gets added when making narrow clones. Differential Revision: https://phab.mercurial-scm.org/D5166

repository: teach addgroup() to receive data with missing parents The way the narrow extension works today, the server rewrites outgoing changegroup data to lie about parents when the parents data is missing. It adds the ellipsis flag to the revision so it can be recorded as such in the revlog. In the new wire protocol, such rewriting does not occur on the server (at least not yet anyway). Instead, it is up to the client to recognize when it has received a revision without its parents. This means rewriting will be performed on the client. Furthermore, the mechanism for storing a shallow revision may differ from store to store. For example, the revlog store uses the ellipsis flag to denote a revision's parents have been rewritten. But a non-revlog store may wish to store things differently. And, some stores may not even support receiving shallow revision data! Therefore, it makes sense for the store itself to be making decisions about what to do when they receive revision data without their parents. This commit teaches the addgroup() bulk insert method to accept a boolean argument that indicates whether the incoming data may lack parent revisions. This flag can be set when receiving "shallow" data from a remote. The revlog implementation of this method has been taught to rewrite the missing parent(s) to nullid and to add the ellipsis flag to the revision when a missing parent is encountered. But it only does this if ellipsis flags are enabled on the repo and the incoming data is marked as possibly shallow. An error occurs otherwise. Differential Revision: https://phab.mercurial-scm.org/D5165

commands: support passing depth to hg.clone() This will allow extensions to add --depth or other arguments to control depth fetching. Differential Revision: https://phab.mercurial-scm.org/D5164

filelog: add a hasnode() method (API) Missing in the file storage interface is the ability to query whether a specified value is a known node. This commit defines that interface member and implements it on the revlog and sqlite file stores. Storage unit tests have been added. The revlog implementation is a bit more complicated because index lookups don't consistently raise the same exception. For SQLite, we can simply look for a key in a dict. Differential Revision: https://phab.mercurial-scm.org/D5163

lfs: consult the narrow matcher when extracting pointers from ctx (issue5794) I added a testcase for lfs to all narrow tests, and the following failed: test-narrow-acl.t test-narrow-exchange.t test-narrow-patterns.t test-narrow-strip.t test-narrow-trackedcmd.t test-narrow-widen.t test-narrow.t The first two still have errors in the pretxnchangegroup on clone and (receiving a) push, which I'm still looking into (4d63f3bc1e1a fixed something in this area already). These two modified tests seem to cover the things that failed in the remaining narrow tests, i.e. `hg tracked` and `hg strip`, so I didn't bother enabling the testcases elsewhere. Maybe we should, but it's 68 tests total.