copies: add a devel debug mode to trace what copy tracing does Mercurial can spend a lot of time finding renames between two commits. Having more information about that process help to understand what makes it slow in an individual instance. (eg: many files vs 1 file, etc...)

revlog: rewrite censoring logic I was able to corrupt a revlog relatively easily with the existing censoring code. The underlying problem is that the existing code doesn't fully take delta chains into account. When copying revisions that occur after the censored revision, the delta base can refer to a censored revision. Then at read time, things blow up due to the revision data not being a compressed delta. This commit rewrites the revlog censoring code to take a higher-level approach. We now create a new revlog instance pointing at temp files. We iterate through each revision in the source revlog and insert those revisions into the new revlog, replacing the censored revision's data along the way. The new implementation isn't as efficient as the old one. This is because it will fully engage delta computation on insertion. But I don't think it matters. The new implementation is a bit hacky because it attempts to reload the revlog instance with a new revlog index/data file. This is fragile. But this is needed because the index (which could be backed by C) would have a cached copy of the old, possibly changed data and that could lead to problems accessing index or revision data later. One benefit of the new approach is that we integrate with the transaction. The old revlog is backed up and if the transaction is rolled back, the original revlog is restored. As part of this, we had to teach the transaction about the store vfs. I'm not super keen about this. But this was the easiest way to hook things up to the transaction. We /could/ just ignore the transaction like we were doing before. But any file mutation should be governed by transaction semantics, including undo during rollback. Differential Revision: https://phab.mercurial-scm.org/D4869

revlog: move loading of index data into own method This will allow us to "reload" a revlog instance from a rewritten index file, which will be used in a subsequent commit. Differential Revision: https://phab.mercurial-scm.org/D4868

revlog: clear revision cache on hash verification failure The revision cache is populated after raw revision fulltext is retrieved but before hash verification. If hash verification fails, the revision cache will be populated and subsequent operations to retrieve the invalid fulltext may return the cached fulltext instead of raising. This commit changes hash verification so it will invalidate the revision cache if the cached node fails hash verification. The side-effect is that subsequent operations to request the revision text - even the raw revision text - will always fail. The new behavior is consistent and is definitely less wrong. There is an open question of whether revision(raw=True) should validate hashes. But I'm going to punt on this problem. We can always change behavior later. And to be honest, I'm not sure we should expose raw=True on the storage interface at all. Another day... Differential Revision: https://phab.mercurial-scm.org/D4867

fuzz: new fuzzer for cext/manifest.c This is a bit messy, because lazymanifest is tightly coupled to the cpython API for performance reasons. As a result, we have to build a whole Python without pymalloc (so ASAN can help us out) and link against that. Then we have to use an embedded Python interpreter. We could manually drive the lazymanifest in C from that point, but experimentally just using PyEval_EvalCode isn't really any slower so we may as well do that and write the innermost guts of the fuzzer in Python. Leak detection is currently disabled for this fuzzer because there are a few global-lifetime things in our extensions that we more or less intentionally leak and I didn't want to take the detour to work around that for now. This should not be pushed to our repo until https://github.com/google/oss-fuzz/pull/1853 is merged, as this depends on having the Python tarball around. Differential Revision: https://phab.mercurial-scm.org/D4879

revlog: rename _cache to _revisioncache "cache" is generic and revlog instances have multiple caches. Let's be descriptive about what this is a cache for. Differential Revision: https://phab.mercurial-scm.org/D4866

testing: add file storage integration for bad hashes and censoring In order to implement these tests, we need a backdoor to write data into storage backends while bypassing normal checks. We invent a callable to do that. As part of writing the tests, I found a bug with censorrevision() pretty quickly! After calling censorrevision(), attempting to access revision data for an affected node raises a cryptic error related to malformed compression. This appears to be due to the revlog not adjusting delta chains as part of censoring. I also found a bug with regards to hash verification and revision fulltext caching. Essentially, we cache the fulltext before hash verification. If we look up the fulltext after a failed hash verification, we don't get a hash verification exception. Furthermore, the behavior of revision(raw=True) can be inconsistent depending on the order of operations. I'll be fixing both these bugs in subsequent commits. Differential Revision: https://phab.mercurial-scm.org/D4865

testing: add file storage tests for getstrippoint() and strip() Differential Revision: https://phab.mercurial-scm.org/D4864

wireprotov2: always advertise raw repo requirements I'm pretty sure my original thinking behind making it conditional on stream clone support was that the behavior mirrored wire protocol version 1. I don't see a compelling reason for us to not advertise the server's storage requirements. The proper way to advertise stream clone support in wireprotov2 would be to not advertise the command(s) required to perform stream clone or to advertise a separate capability denoting stream clone support. Stream clone isn't yet implemented on wireprotov2, so we can cross this bridge later. Differential Revision: https://phab.mercurial-scm.org/D4863

tests: don't be as verbose in wireprotov2 tests I don't think that printing low-level I/O and frames is beneficial to testing command-level functionality. Protocol-level testing, yes. But command-level functionality shouldn't care about low-level details in most cases. This output makes tests more verbose and harder to read. It also makes them harder to maintain, as you need to glob over various dynamic width fields. Let's remove these low-level details from many of the wireprotov2 tests. Differential Revision: https://phab.mercurial-scm.org/D4861

repository: define and use revision flag constants Revlogs have a per-revision 2 byte field holding integer flags that define how revision data should be interpreted. For historical reasons, these integer values are sent verbatim on the wire protocol as part of changegroup data. From a semantic standpoint, the flags that go out over the wire are different from the flags stored internally by revlogs. Failure to establish this semantic distinction creates unwanted strong coupling between revlog's internals and the wire protocol. This commit establishes new constants on the repository module that define the revision flags used by the wire protocol (and by some internal storage APIs, sadly). The changegroups internals documentation has been updated to document them explicitly. Various references throughout the repo now use the repository constants instead of the revlog constants. This is done to make it clear that we're operating on generic revision data and this isn't tied to revlogs. Differential Revision: https://phab.mercurial-scm.org/D4860

context: reverse conditional branch order in introrev Positive logic will be simpler to follow. It will help to clarify coming refactoring.

context: drop a redundant fast path in introrev Now that _adjustlinkrev fast path this case itself, we no longer need an extra conditional. A nice side effect is that we are no longer calling `self.rev()`. In case where `_descendantrev` is set, calling `self.rev` will trigger a potentially expensive `_adjustlinkrev` call. So blindly calling `self.rev()` to avoid another `_adjustlinkrev` call can be counterproductive. Note that `_descendantrev` is currently never taken into account in `introrev` so far which is wrong. We'll fix that in changeset later in this series.

context: fast path linkrev adjustement in trivial case If the search starts from the linkrev, there is nothing to adjust.

url: allow to configure timeout on http connection By default, httplib.HTTPConnection opens connection with no timeout. If the server is hanging, Mercurial will wait indefinitely. This may be an issue for automated scripts. Differential Revision: https://phab.mercurial-scm.org/D4878

obsolete: explicitly track folds inside the markers We now record information to be able to recognize "fold" event from obsolescence markers. To do so, we track the following pieces of information: a) a fold ID. Unique to that fold (per successor), b) the number of predecessors, c) the index of the predecessor in that fold. We will now be able to create an algorithm able to find "predecessorssets". We now store this data in the generic "metadata" field of the markers. Updating the format to have a more compact storage for this would be useful. This way of tracking a fold through multiple markers could be applied to split too. This would have two advantages: 1) We get a simpler format, since number of successors is limited to [0-1]. 2) We can better deal with situations where only some of the split successors are pushed to a remote repository. We should look into the relevance of such a change before updating the on-disk format. note: unlike splits, folds do not have to deal with cases where only some of the markers have been synchronized. As they all share the same successor changesets, they are all relevant to the same nodes.

cleanupnodes: update comment to drop mention of filtering Since changeset 1857f50a9643 drop the filtering, we should not longer mention it in code comment.

treemanifests: remove _loadalllazy when doing copies 'before' here is https://phab.mercurial-scm.org/D4845 (not the committed/rebased version) diff --git: repo | N | T | before (mean +- stdev) | after (mean +- stdev) | % of before ------+---+---+------------------------+-----------------------+------------ m-u | | | 1.329 s +- 0.011 s | 1.320 s +- 0.010 s | 99.3% m-u | | x | 1.316 s +- 0.005 s | 1.334 s +- 0.018 s | 101.4% m-u | x | | 1.330 s +- 0.021 s | 1.322 s +- 0.005 s | 99.4% m-u | x | x | 87.2 ms +- 0.7 ms | 86.9 ms +- 1.5 ms | 99.7% l-d-r | | | 203.3 ms +- 7.8 ms | 199.4 ms +- 1.8 ms | 98.1% l-d-r | | x | 204.6 ms +- 2.8 ms | 201.7 ms +- 2.1 ms | 98.6% l-d-r | x | | 90.5 ms +- 11.0 ms | 86.2 ms +- 1.0 ms | 95.2% l-d-r | x | x | 66.3 ms +- 2.0 ms | 66.4 ms +- 0.9 ms | 100.2% diff -c . --git: repo | N | T | before (mean +- stdev) | after (mean +- stdev) | % of before ------+---+---+------------------------+-----------------------+------------ m-u | | | 239.4 ms +- 2.0 ms | 241.7 ms +- 4.6 ms | 101.0% m-u | | x | 128.9 ms +- 1.9 ms | 130.9 ms +- 7.7 ms | 101.6% m-u | x | | 241.1 ms +- 1.6 ms | 240.1 ms +- 1.4 ms | 99.6% m-u | x | x | 133.4 ms +- 1.5 ms | 133.4 ms +- 1.2 ms | 100.0% l-d-r | | | 84.3 ms +- 1.5 ms | 83.5 ms +- 1.0 ms | 99.1% l-d-r | | x | 200.9 ms +- 6.3 ms | 203.0 ms +- 4.4 ms | 101.0% l-d-r | x | | 108.1 ms +- 1.4 ms | 108.7 ms +- 2.1 ms | 100.6% l-d-r | x | x | 190.2 ms +- 4.8 ms | 191.6 ms +- 2.0 ms | 100.7% rebase -r . --keep -d .^^: repo | N | T | before (mean +- stdev) | after (mean +- stdev) | % of before ------+---+---+------------------------+-----------------------+------------ m-u | | | 5.655 s +- 0.029 s | 5.640 s +- 0.036 s | 99.7% m-u | | x | 5.813 s +- 0.038 s | 5.773 s +- 0.028 s | 99.3% m-u | x | | 5.593 s +- 0.043 s | 5.589 s +- 0.028 s | 99.9% m-u | x | x | 648.2 ms +- 19.2 ms | 637.3 ms +- 27.7 ms | 98.3% l-d-r | | | 673.3 ms +- 8.0 ms | 673.2 ms +- 6.8 ms | 100.0% l-d-r | | x | 6.583 s +- 0.030 s | 5.721 s +- 0.028 s | 86.9% <-- l-d-r | x | | 277.8 ms +- 6.7 ms | 276.0 ms +- 2.7 ms | 99.4% l-d-r | x | x | 1.692 s +- 0.013 s | 720.9 ms +- 13.3 ms | 42.6% <-- status --change . --copies: repo | N | T | before (mean +- stdev) | after (mean +- stdev) | % of before ------+---+---+------------------------+-----------------------+------------ m-u | | | 220.9 ms +- 1.6 ms | 219.9 ms +- 2.2 ms | 99.5% m-u | | x | 109.2 ms +- 1.0 ms | 109.4 ms +- 0.8 ms | 100.2% m-u | x | | 222.6 ms +- 1.7 ms | 221.4 ms +- 2.1 ms | 99.5% m-u | x | x | 113.4 ms +- 0.5 ms | 113.1 ms +- 1.1 ms | 99.7% l-d-r | | | 82.1 ms +- 1.7 ms | 82.1 ms +- 1.2 ms | 100.0% l-d-r | | x | 199.8 ms +- 4.0 ms | 200.7 ms +- 3.6 ms | 100.5% l-d-r | x | | 85.4 ms +- 1.5 ms | 85.2 ms +- 0.3 ms | 99.8% l-d-r | x | x | 202.6 ms +- 4.4 ms | 208.0 ms +- 4.0 ms | 102.7% status --copies: repo | N | T | before (mean +- stdev) | after (mean +- stdev) | % of before ------+---+---+------------------------+-----------------------+------------ m-u | | | 1.941 s +- 0.014 s | 1.930 s +- 0.009 s | 99.4% m-u | | x | 1.924 s +- 0.007 s | 1.950 s +- 0.010 s | 101.4% m-u | x | | 1.959 s +- 0.085 s | 1.926 s +- 0.009 s | 98.3% m-u | x | x | 96.2 ms +- 1.0 ms | 96.4 ms +- 0.7 ms | 100.2% l-d-r | | | 604.4 ms +- 10.6 ms | 602.6 ms +- 7.1 ms | 99.7% l-d-r | | x | 605.7 ms +- 4.1 ms | 607.4 ms +- 6.1 ms | 100.3% l-d-r | x | | 182.4 ms +- 1.2 ms | 183.4 ms +- 1.2 ms | 100.5% l-d-r | x | x | 150.8 ms +- 2.0 ms | 150.6 ms +- 1.0 ms | 99.9% update $rev^; ~/src/hg/hg{hg}/hg update $rev: repo | N | T | before (mean +- stdev) | after (mean +- stdev) | % of before ------+---+---+------------------------+-----------------------+------------ m-u | | | 3.185 s +- 0.027 s | 3.181 s +- 0.017 s | 99.9% m-u | | x | 3.028 s +- 0.021 s | 2.954 s +- 0.010 s | 97.6% m-u | x | | 3.168 s +- 0.010 s | 3.175 s +- 0.023 s | 100.2% m-u | x | x | 317.5 ms +- 3.5 ms | 313.2 ms +- 2.9 ms | 98.6% l-d-r | | | 456.2 ms +- 10.6 ms | 454.4 ms +- 5.8 ms | 99.6% l-d-r | | x | 9.236 s +- 0.063 s | 757.9 ms +- 9.2 ms | 8.2% <-- l-d-r | x | | 257.6 ms +- 2.3 ms | 261.2 ms +- 1.7 ms | 101.4% l-d-r | x | x | 1.614 s +- 0.013 s | 478.0 ms +- 14.3 ms | 29.6% <-- Differential Revision: https://phab.mercurial-scm.org/D4875

treemanifests: store whether a lazydirs entry needs copied after materializing Due to the way that things like manifestlog.get caches its values, without making a copy (if necessary) after calling readsubtree(), we might end up adjusting the state of the same object on different contexts, breaking things like dirty state tracking (and probably other things). Differential Revision: https://phab.mercurial-scm.org/D4874

treemanifests: extract _loaddifflazy from _diff, use in _filesnotin Differential Revision: https://phab.mercurial-scm.org/D4873

identify: show remote bookmarks in `hg id url -Tjson -B` I didn't display bookmarks when `default and not ui.quiet`: it seems strange for templates to depend on --id or -q, and it would take more code for `hg id url -T {node}` to not request remote bookmarks. An alternative I thought of was providing lazy data to the formatter, `fm.data(bookmarks=lambda: fm.formatlist(getbms(), name='bookmark'))`. The plainformatter would naturally not compute it, the templateformatter would compute only what it needs, and the other ones would compute everything, but that's not supported (or I don't see how), so I abandoned this idea. Differential Revision: https://phab.mercurial-scm.org/D4872

showstack: also handle SIGALRM This is looking *very* handy when debugging mysterious hangs in a test: you can wrap a hanging invocation in `perl -e 'alarm shift @ARGV; exec @ARGV' 1` for example, a hanging `hg pull` becomes `perl -e 'alarm shift @ARGV; exec @ARGV' 1 hg pull` where the `1` is the timeout in seconds before the process will be hit with SIGALRM. After making that edit to the test file, you can then use --extra-config-opt on run-tests.py to globaly enable showstack during the test run, so you'll get full stack traces as you force your hg to exit. I wonder (but only a little, not enough to take action just yet) if we should wire up some scaffolding in run-tests itself to automatically wrap all commands in alarm(3) somehow to avoid hangs in the future? Differential Revision: https://phab.mercurial-scm.org/D4870

exchangev2: add progress bar around manifest scanning This can take a long time on large repositories. Let's add a progress bar so we don't have long periods where it isn't obvious what is going on. Differential Revision: https://phab.mercurial-scm.org/D4859

httppeer: report http statistics Now that keepalive.py records HTTP request count and the number of bytes sent and received as part of performing those requests, we can easily print a report on the activity when closing a peer instance! Exact byte counts are globbed in tests because they are influenced by non-deterministic things, such as hostnames and port numbers. Plus, the exact byte count isn't too important anyway. I feel obliged to note that printing the byte count could have security implications. e.g. if sending a password via HTTP basic auth, the length of that password will influence the byte count and the reporting of the byte count could be a side-channel leak of the password length. I /think/ this is beyond our threshold for concern. But if we think it poses a problem, we can teach the byte count logging code to e.g. ignore sensitive HTTP request headers. We could also consider not reporting the byte count of request headers altogether. But since the wire protocol uses HTTP headers for sending command arguments, it is kind of important to report their size. Differential Revision: https://phab.mercurial-scm.org/D4858

keepalive: track number of bytes received from an HTTP response We also bubble the byte count up to the HTTPConnection instance and its parent opener at read time. Unlike sending, there isn't a clear "end of response" signal we can intercept to defer updating the accounting. Differential Revision: https://phab.mercurial-scm.org/D4857

keepalive: track request count and bytes sent I want wire protocol interactions to report the number of requests made and bytes transferred. This commit teaches the very low-level custom HTTPConnection class to track the number of bytes sent to the socket. This may vary from the number of bytes that go on the wire due to e.g. TLS. That's OK. KeepAliveHandler is taught to track the total number of requests and total number of bytes sent across all requests. Differential Revision: https://phab.mercurial-scm.org/D4856

url: have httpsconnection inherit from our custom HTTPConnection This will ensure that any customizations we perform to HTTPConnection will be available to httpsconnection. Differential Revision: https://phab.mercurial-scm.org/D4855

cborutil: change buffering strategy Profiling revealed that we were spending a lot of time on the line that was concatenating the old buffer with the incoming data when attempting to decode long byte strings, such as manifest revisions. Essentially, we were feeding N chunks of size len(X) << len(Y) into decode() and continuously allocating a new, larger buffer to hold the undecoded input. This created substantial memory churn and slowed down execution. Changing the code to aggregate pending chunks in a list until we have enough data to fully decode the next atom makes things much more efficient. I don't have exact data, but I recall the old code spending >1s on manifest fulltexts from the mozilla-unified repo. The new code doesn't significantly appear in profile output. Differential Revision: https://phab.mercurial-scm.org/D4854

cleanup: some Yoda conditions, this patch removes It seems the factor 20 is less than the frequency of " < \d" compared to " \d > ". Differential Revision: https://phab.mercurial-scm.org/D4862

streamclone: don't support stream clone unless repo feature present This change means custom repository types must opt in to enabling stream clone. This seems reasonable, as stream clones are a very low-level feature that has historically assumed the use of revlogs and the layout of .hg/ that they entail. Differential Revision: https://phab.mercurial-scm.org/D4853