bundle2: keep hint close to the primary message when remote abort The remote hint message was ignored when reporting the remote error and passed to the local generic abort error. I think I might initially have tried to avoid reimplementing logic controlling the hint display depending of the verbosity level. However, first, there does not seems to have such verbosity related logic and second the resulting was wrong as the primary error and the hint were split apart. We now properly print the hint as remote output.

misc: update year in copyright lines This patch also makes some expected output lines in tests glob-ed for persistence of them. BTW, files below aren't yet changed in 2017, but this patch also updates copyright of them, because: - mercurial/help/hg.1.txt almost all of "man hg" output comes from online help of hg command, and is already changed in 2017 - mercurial/help/hgignore.5.txt - mercurial/help/hgrc.5 "copyright 2005-201X Matt Mackall" in them mentions about copyright of Mercurial itself

localrepo: avoid unnecessary sorting headrevs output already sorted, no need to sort it again.

localrepo: cache self.changelog in local variable Repeated self.changelog lookups can incur overhead. Let's cache it in the separate variable.

destutil: remove dead code about non-linear updates IIUC, the non-linear updates no longer happen by default since 6b1fc09c699a (update: change default destination to tipmost descendant (issue4673) (BC), 2016-02-02), and it was only if they happened by default that we used to error out, so there is no longer a need to handle this case.

update: fix typo/stale comment to match code The comment about "obsolete.background" seems to have been about obsolete.foreground ever since it was introduced in a59e575c6ff8 (update: allow dirty update to foreground (successors), 2013-04-16), so let's change it.

merge: remove unused handling of default destination in merge.update() As far as I can tell, all the callers of merge.update() have been migrated over to use destutil to find the default destination when the revision was not specified. So it's time to delete the code for handling a node value of None. Let's add an assertion that node is not None, so any extensions relying on it will not silently misbehave.

update: localize logic around which ancestor to use The merge code works by applying the changes between an ancestor and the working copy onto the destination. To achieve an update, it sets the ancestor to be the parent of the working copy. To achieve a clean update (update -C), it sets the ancestor to be the working copy itself (so there are no changes to carry over). The logic for this was spread out a bit. Let's move it all to one place so it's easier to follow the reason for it. Also add some documentation.

tests: add test for updating to null revision While working on merge.py, I realized that we don't (as far as I could tell) have any tests for updating to the null revision with a dirty working copy. This adds some simple tests for that.

import: mention "stdin" (abbreviated) and add example I actually didn't even think it was possible because I searched the help text for "stdin", and didn't even think of searching for "standard input". Let's mention the abbreviated form too to help others like me. (When importing from stdin, we actually print a message saying "applying patch from stdin".) This patch also adds an example showing how to import from stdin.

merge: print status message before launching external merge tool It seems somewhat common that people run into a merge conflict and don't notice the launched merge tool, and instead they think hg just hung. Let's print a message for each file that we launch a GUI merge tool for.

pager: exit cleanly on SIGPIPE (BC) Changeset aaa751585325 removes SIGPIPE handling completely. This is wrong, as it means that Mercurial does not exit when the pager does. Instead, raise SignalInterrupt when SIGPIPE happens with a pager attached, to trigger the normal exit path. This will cause "killed!" to be printed to stderr (hence the BC warning), but in the normal pager use case (where the pager gets both stderr and stdout), this message is lost as we only get SIGPIPE when the pager quits.

runtests: catch EPROTONOSUPPORT in checkportisavailable This is a follow-up of "runtests: check ports on IPv6 address". On some platforms, "socket.AF_INET6" exists while that does not necessarily mean the platform support IPv6 - when initializing a socket using "socket.socket", it could fail with EPROTONOSUPPORT. So treat that as "Port unavailable".

zstd: vendor python-zstandard 0.7.0 Commit 3054ae3a66112970a091d3939fee32c2d0c1a23e from https://github.com/indygreg/python-zstandard is imported without modifications (other than removing unwanted files). The vendored zstd library within has been upgraded from 1.1.2 to 1.1.3. This version introduced new APIs for threads, thread pools, multi-threaded compression, and a new dictionary builder (COVER). These features are not yet used by python-zstandard (or Mercurial for that matter). However, that will likely change in the next python-zstandard release (and I think there are opportunities for Mercurial to take advantage of the multi-threaded APIs). Relevant to Mercurial, the CFFI bindings are now fully implemented. This means zstd should "just work" with PyPy (although I haven't tried). The python-zstandard test suite also runs all tests against both the C extension and CFFI bindings to ensure feature parity. There is also a "decompress_content_dict_chain()" API. This was derived from discussions with Yann Collet on list about alternate ways of encoding delta chains. The change most relevant to Mercurial is a performance enhancement in the simple decompression API to reuse a data structure across operations. This makes decompression of multiple inputs significantly faster. (This scenario occurs when reading revlog delta chains, for example.) Using python-zstandard's bench.py to measure the performance difference... On changelog chunks in the mozilla-unified repo: decompress discrete decompress() reuse zctx 1.262243 wall; 1.260000 CPU; 1.260000 user; 0.000000 sys 170.43 MB/s (best of 3) 0.949106 wall; 0.950000 CPU; 0.950000 user; 0.000000 sys 226.66 MB/s (best of 4) decompress discrete dict decompress() reuse zctx 0.692170 wall; 0.690000 CPU; 0.690000 user; 0.000000 sys 310.80 MB/s (best of 5) 0.437088 wall; 0.440000 CPU; 0.440000 user; 0.000000 sys 492.17 MB/s (best of 7) On manifest chunks in the mozilla-unified repo: decompress discrete decompress() reuse zctx 1.367284 wall; 1.370000 CPU; 1.370000 user; 0.000000 sys 274.01 MB/s (best of 3) 1.086831 wall; 1.080000 CPU; 1.080000 user; 0.000000 sys 344.72 MB/s (best of 3) decompress discrete dict decompress() reuse zctx 0.993272 wall; 0.990000 CPU; 0.990000 user; 0.000000 sys 377.19 MB/s (best of 3) 0.678651 wall; 0.680000 CPU; 0.680000 user; 0.000000 sys 552.06 MB/s (best of 5) That should make reads on zstd revlogs a bit faster ;) # no-check-commit

tests: exclude python-zstandard from pyflakes analysis

py3: fix the way we produce bytes list in store.py bytes(range(127)) does not produce a list whereas we need a list. This patch fixes that.

py3: convert os.__file__ to bytes os.__file__ returns unicode path on Python 3. We need to have bytespath. This patch uses pycompat.fsencode() to encode unicode path to bytes path.

commandserver: handle backlog before exiting Previously, when a chg server is exiting, it does not handle connected clients so clients may get ECONNRESET and crash: 1. client connect() # success 2. server shouldexit = True and exit 3. client recv() # ECONNRESET d7875bfbfccb makes this race condition easier to reproduce if a lot of short chg commands are started in parallel. This patch fixes the above issue by unlinking the socket path to stop queuing new connections and processing all pending connections before exit.

misc: replace domain of mercurial-devel ML address by mercurial-scm.org This patch also adds new check-code.py pattern to detect invalid usage of "mercurial-devel@selenic.com".

i18n: update Report-Msgid-Bugs-To property of *.po files This patch replaces domain of mercurial-devel ML address by mercurial-scm.org for "Report-Msgid-Bugs-To" property of each *.po files. This avoids releasing 4.1.1 with invalid "Report-Msgid-Bugs-To" in *.mo file, if corresponded *.po file isn't msgmerge-ed with recent hg.pot by translator. These *.po files aren't covered by check-code.py pattern newly added in subsequent patch, because it ignores them.

misc: replace domain of mercurial ML address by mercurial-scm.org This patch also adds new check-code.py pattern to detect invalid usage of "mercurial@selenic.com". Change for test-convert-tla.t is tested, but similar change for almost same test-convert-baz.t isn't yet tested actually, because I couldn't find out the way to get "GNU Arch baz client". AFAIK, buildbot skips test-convert-baz.t, too. Does anybody have appropriate environment for testing?

commandserver: prevent unlink socket twice This patch changes unixforkingservice so it only calls `self._servicehandler.unlinksocket(self.address)` at most once. This is needed by the next patch.

runtests: check ports on IPv6 address Previously, checkportisavailable only checks ports on the IPv4 address. This patch makes it check IPv6 as well. It'll be useful if "localhost" does not have an IPv4 address, or its IPv4 address does not exist somehow.

zeroconf: fail nicely on IPv6 only system zeroconf only knows how to deal with IPv4; I develop on a system where the only IPv4 address is 127.0.0.1. Teach zeroconf to ignore IPv6 addresses when looking for plausible IPv4 connectivity.

chg: verify XDG_RUNTIME_DIR According to the specification [1], $XDG_RUNTIME_DIR should be ignored unless: The directory MUST be owned by the user, and he MUST be the only one having read and write access to it. Its Unix access mode MUST be 0700. This patch adds a check and ignores it if it does not meet part of the criteria. [1]: https://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html

check-code: permit functools.reduce

perf: split obtaining chunks from decompression Previously, the code was similar to what revlog._chunks() was doing, which took a raw data segment and delta chain, obtained buffers for the raw revlog chunks within, and decompressed them. This commit splits the "get raw chunks" action from "decompress." The goal of this change is to more accurately measurely decompression performance. On a ~50k deltachain for a manifest in mozilla-central: ! full ! wall 0.430548 comb 0.440000 user 0.410000 sys 0.030000 (best of 24) ! deltachain ! wall 0.016053 comb 0.010000 user 0.010000 sys 0.000000 (best of 181) ! read ! wall 0.008078 comb 0.010000 user 0.000000 sys 0.010000 (best of 362) ! rawchunks ! wall 0.033785 comb 0.040000 user 0.040000 sys 0.000000 (best of 100) ! decompress ! wall 0.327126 comb 0.320000 user 0.320000 sys 0.000000 (best of 31) ! patch ! wall 0.032391 comb 0.030000 user 0.030000 sys 0.000000 (best of 100) ! hash ! wall 0.012587 comb 0.010000 user 0.010000 sys 0.000000 (best of 233)

smartset: move set classes and related functions from revset module (API) These classes are pretty large and independent from revset computation. 2961 mercurial/revset.py 973 mercurial/smartset.py 3934 total revset.prettyformatset() is renamed to smartset.prettyformat(). Smartset classes are aliased since they are quite common in revset.py.

help: test if "hg help TOPIC" reference is valid It's quite easy to make a reference invalid by mistake.

help: uppercase command placeholder 'command' isn't a valid help topic but a placeholder text. Make it upper case to avoid confusion.

help: show section that couldn't be found For better error indication.

cmdutil: remove forwarding methods per deprecation policy

util: always force line buffered stdout when stdout is a tty (BC) pager replaced stdout with a line buffered version to work around glibc deciding on a buffering strategy on the first write to stdout. This is going to make my next patch hard, as replacing stdout will make tracking time spent blocked on it more challenging. Move the line buffering requirement to util.py, and remove it from pager. This means that the abuse of ui.formatted=True and pager set to cat or equivalent no longer results in a line-buffered output to a pipe, hence (BC), although I don't expect anyone to be affected

localrepo: avoid unnecessary conversion from node to rev changelog.heads() first calls headrevs then converts them to nodes. localrepo.heads() then sorts them using self.changelog.rev function and makes useless conversion back to revs. Instead let's call changelog.headrevs() from localrepo.heads(), sort the output and then convert to nodes. Because headrevs does not support start parameter this optimization only works if start is None.

debian: update copyright years

debian: update mailing list address

bundle2: implement a basic __repr__ for bundle2 part We display basic data as the part id and part type. This make debugging bundle2 related code friendlier.

bundle2: drop an outdated comment The function is no longer in "early" stage and have been used in production for years. We can probably drop that part of the docstring...

unbundle: swap conditional branches for clarity This is a small style update for clarity. The previous situation was: if foo: 50 lines else: 2 lines In such case I tend to invert these to get the simpler branch out of the way earlier: if not foo: 2 lines else: 50 lines This makes the conditional and various alternatives fit on the same screen, simpler to read overall.

unbundle: add a small comment to tag the bundle1 case as such This makes the code clearer to understand for someone new to it (or rusted)

unbundle: add a small comment to clarify the 'check_heads' call Bundle2 has its own mechanisms to check for heads (and other) changes, so push using bundle2 is relying on the "check:heads" bundle part of unbundle and the 'check_heads' call is not checking anything. We add a small comment to make this clearer.

pager: don't terminate with extreme prejudice on SIGPIPE (BC) The default SIGPIPE handler causes Mercurial to exit immediately, without running any Python cleanup code (except and finally blocks, atexit handlers etc). This creates problems if you want to do something at exit. If we need a different exit code for broken pipe from pager, then we should code that ourselves in Python; this appears to have been cargo-culted from the fork implementation of pager that's no longer used, where it was needed to stop Broken Pipe errors appearing on the user's terminal.

verify: replace _validpath() by matcher The verifier calls out to _validpath() to check if it should verify that path and the narrowhg extension overrides _validpath() to tell the verifier to skip that path. In treemanifest repos, the verifier calls the same method to check if it should visit a directory. However, the decision to visit a directory is different from the condition that it's a matching path, and narrowhg was working around it by returning True from its _validpath() override if *either* was true. Similar to how one can do "hg files -I foo/bar/ -X foo/" (making the include pointless), narrowhg can be configured to track the same paths. In that case match("foo/bar/baz") would be false, but match.visitdir("foo/bar/baz") turns out to be true, causing verify to fail. This may seem like a bug in visitdir(), but it's explicitly documented to be undefined for subdirectories of excluded directories. When using treemanifests, the walk would not descend into foo/, so verification would pass. However, when using flat manifests, there is no recursive directory walk and the file path "foo/bar/baz" would be passed to _validpath() without "foo/" (actually without the slash) being passed first. As explained above, _validpath() would return true for the file path and "hg verify" would fail. Replacing the _validpath() method by a matcher seems like the obvious fix. Narrowhg can then pass in its own matcher and not have to conflate the two matching functions (for dirs and files). I think it also makes the code clearer.

rebase: fix code comment to refer to right issue (4504, not 4505) The comment was introduced in 8a544fb645bb (rebase: ensure rebase revision remains visible (issue4504), 2015-01-27), which mentions the right issue in the description.

merge with stable

Added signature for changeset e1526da1e6d8

Added tag 4.1 for changeset e1526da1e6d8

merge with i18n

i18n-pt_BR: synchronized with dfc6663f97ca

merge: more safe detection of criss cross merge conflict between dm and r 41f6af50c0d8 introduced handling of a crash in this case. A review comment suggested that it was not entirely obvious that a 'dm' always would have a 'r' for the source file. To mitigate that risk, make the code more conservative and make less assumptions.

tests: correct (I think) command in test-largefiles-update When this test was introduced, it used the short-form of all the flags on this update invocation. I suspect, based on the "start with clean dirstates" comment and the fact that the no-exec branch of the #if guard leaves dirstate clean, that this should have been 'update -qCr' instead of 'update -qcr', but that a bug in largefiles --check handling left this problem unnoticed. I'll leave a breadcrumb further up about the current failure mode in the hopes that we can fix this some day. This was previously discussed in [0] but the trail in that thread goes cold after a few replies. Given that this is still a flaky test, that appears to only be passing by bad fortune, I think it's worth correcting the code of the test to make a correct assertion, and to keep track of the suspected bug with some other mechanism than an invalid test (if we had support for "expected failure" blocks this might be a worthwhile use of them?). 0: https://www.mercurial-scm.org/pipermail/mercurial-devel/2016-October/089501.html

tests: expand flags to long form in test-largefiles-update.t I spent some time confused by this test. I'm pretty sure that this line intends to be cleaning the dirstate, not checking that it's clean before updating: the preceding #if block leaves the dirstate clean in the noexec case, and dirty in the exec case, so we can't expect consistent behavior across that platform variation. A subsequent patch will modify this command to use --clean instead of --check. I'll elaborate in that patch about the hypothetical bug here.

merge: fix crash on criss cross merge with dir move and delete (issue5020) Work around that 'dm' in the data model only can have one operation for the target file, but still can have multiple and conflicting operations on the source file where the other operation is a 'rm'. The move would thus fail with 'abort: No such file or directory'. In this case it is "obvious" that the file should be removed, either before or after moving it. We thus keep the 'rm' of the source file but drop the 'dm'. This is not a pretty fix but quite "obviously" safe (famous last words...) as it only touches a rare code path that used to crash. It is possible that it would be better to swap the files for 'dm' as suggested on https://bz.mercurial-scm.org/show_bug.cgi?id=5020#c13 but it is not entirely obvious that it not just would create conflicts on the other file. That can be revisited later.

tests: use 'f' in test-merge-criss-cross.t to prepare for recursive dumping Prepare for adding a test case with files in a directory.

util: make sortdict.keys() return a copy dict.keys() is documented to return a copy, so it's surprising that sortdict.keys() did not. I noticed this because we have an extension that calls readlocaltags(). That method tries to remove any tags that point to non-existent revisions (most likely stripped). However, since it's unintentionally working on the instance it's modifying, it sometimes fails to remove tags when there are multiple bad tags in a row. This was not caught because localrepo.tags() does an additional layer of filtering. sortdict is also used in other places, but I have not checked whether its keys() and/or __delitem__() methods are used there.

test-highlight: add normalization rule for Pygments 2.2 The test failed on Debian sid because of new class="vm".

tests: account for different newline behavior between Solaris and GNU grep GNU grep, when emitting a matching line that doesn't have a terminating newline, will add an extra newline. Solaris grep passes the original line through without the newline. This causes differences in test output when looking at the last line of the output of get-with-headers.py, which doesn't usually emit (and certainly doesn't guarantee) a terminating newline. Both grep implementations succeed in matching the requested pattern, though, so rely on specifying the full pattern on grep's commandline instead of expecting it in the output, and send the output to /dev/null.

tests: also allow "Protocol not supported" in test-http-proxy error I've seen this in a (misconfigured) FreeBSD jail which has ::1 as an entry for localhost, but IPv6 support is disabled in the jail. It took me months to figure out what was going on (and I only figured it out when tinyproxy.py got confused by similar IPv4-level misconfiguration of the localhost domain in /etc/hosts.) I don't feel strongly about this patch: on the one hand, it's papering over a host-level misconfiguration, but on the other it avoids some weird and hard to diagnose problems that can occur in weirdly restricted environments.

revset: prevent using outgoing() and remote() in hgweb session (BC) outgoing() and remote() may stall for long due to network I/O, which seems unsafe per definition, "whether a predicate is safe for DoS attack." But I'm not 100% sure about this. If our concern isn't elapsed time but CPU resource, these predicates are considered safe. Perhaps that would be up to the web/application server configuration? Anyway, outgoing() and remote() wouldn't be useful in hgweb, so I think it's okay to ban them.

tests: use an absolute path to get around '..' being invalid on a dead CWD Only FreeBSD seems to be this picky. Note that this explicit absolute-path `cd` exposes a defect in the test, in that we end up still inside the cwd-vanish repository, but that's not a regression in this change. Since we're in a code freeze, I'm doing the smallest thing possible to try and fix bugs on FreeBSD, rather than cleaning up the entire problem. I'll follow up with a more complete fix after the freeze.

ui: rename tmpdir parameter to more specific repopath This was requested by Augie and I agree that repopath is more descriptive.

pager: wrap _runcommand() no matter if stdout is redirected We've made chg utilize the common code path implemented in pager.py (by 815e1cefd082 and 493935e0327a), but the chg server does not always start with a tty. Because of this, uisetup() of the pager extension could be skipped on the chg server. Kudos given to Sean Farley for dogfooding new chg and spotting this problem.

shelve: make unshelve not crash when there are missing files (issue4176) This patch makes it possible to unshelve while having missing files in your repo as long as shelved changes don't touch those missing files. It also makes error message better otherwise.

statprof: require input file statprof has a __main__ handler that allows viewing of previously written data files. As Yuya pointed out during review, f42cd5434cc2 broke this. This patch fixes that.

tests: work around FreeBSD's unzip having slightly different output According to man 1 unzip, this unzip appeared in FreeBSD 8.0. It's what comes as /usr/bin/unzip, so we may as well cater to it since it's easy.

contrib: fix check-commit to not reject commits from `hg sign` and `hg tag` I'm tired of having a spurious red build every time we do a release. Fix it once and for all.

Added signature for changeset a1dd2c0c479e

Added tag 4.1-rc for changeset a1dd2c0c479e

tests: fix up some http tests for no-zstd case

freeze: merge default into stable for 4.1 code freeze

patchbomb: add tmpdir parameter to ui.edit call

histedit: add tmpdir parameter to ui.edit call

cmdutil: add tmpdir parament to ui.edit calls

ui: add a parameter to set the temporary directory for edit Until callsites are updated, this will have no effect. Once callsites are updated, specifying experimental.editortmpinhg will create editor temporary files in a subdirectory of .hg, which will make it easier for tool integrations to determine what repository is in play when they're asked to edit an hg-related file.

help: update help for `hg update` which was misleading (issue5427)

templater: add '{envvars}' to access environment variables Since the option for ui.exportableenviron is experimental, so is this template until the underlying API is sorted out.

ui: introduce an experimental dict of exportable environment variables Care needs to be taken to prevent leaking potentially sensitive environment variables through hgweb, if template support for environment variables is to be introduced. There are a few ideas about the API for preventing accidental leaking [1]. Option 3 seems best from the POV of not needing to configure anything in the normal case. I couldn't figure out how to do that, so guard it with an experimental option for now. [1] https://www.mercurial-scm.org/pipermail/mercurial-devel/2017-January/092383.html

tests: test experimental.spacemovesdown config for commit -i The feature is still very experimental, but at least its behavior is captured in the test.

zstd: prevent potential free() of uninitialized memory This is a cherry pick of an upstream fix. The free() of uninitialed memory could likely only occur if a malloc() inside zstd fails. The patched functions aren't currently used by Mercurial. But I don't like leaving footguns sitting around.

revlog: give EXTSTORED flag value to narrowhg Narrowhg has been using "1 << 14" as its revlog flag value for a long time. We (Google) have many repos with that value in production already. When the same value was reserved for EXTSTORED, it made those repos invalid. Upgrading them will be a little painful. We should clearly have reserved the value for narrowhg a long time ago. Since the EXTSTORED flag is not yet in any release and Facebook also says they have not started using it in production, so it should be okay to change it. This patch gives the current value (1 << 14) back to narrowhg and gives a new value (1 << 13) to EXTSTORED.

help: don't let tools reflow revlog flags list Before this change, the text about revlog flags was reflowed into a single paragraph, which made it a bit hard to read. I don't even know the rules around this, but adding a blank line before each flag seems to prevent the reflowing.

help: format revlog.txt more closely to result The rendered text has spaces before each item in the list

hgweb: simplify calculation of first revision in filelog command

hgweb: restore ascending iteration on revs in filelog web command Follow-up on 96f811bceb85. Adjust back the "parity" generator's offset to keep rendering the same.

context: extract _changesinrange() out of blockancestors() We'll need it to write a blockdescendants function in next changeset.

shelve: allow multiple shelves with --patch and --stat Before this patch, there was a single way to see multiple shelves using `--patch --list` which show all the shelves. Doing `--patch s1 s2` returns an error. This patch allows to show multiple shelves using `--patch` and `--stat`.

zstd: vendor python-zstandard 0.6.0 Commit 63c68d6f5fc8de4afd9bde81b13b537beb4e47e8 from https://github.com/indygreg/python-zstandard is imported without modifications (other than removing unwanted files). This includes minor performance and feature improvements. It also changes the vendored zstd library from 1.1.1 to 1.1.2. # no-check-commit

util: add length argument to util.buffer() util.buffer() either returns inbuilt buffer function or defines a new one which slices. The inbuilt buffer() also has a length argument which is missing from the ones we defined. This patch adds that length argument.

py3: replace pycompat.getenv with encoding.environ.get pycompat.getenv returns os.getenvb on py3 which is not available on Windows. This patch replaces them with encoding.environ.get and checks to ensure no new instances of os.getenv or os.setenv are introduced.

patch: check length of git index header only if integer is specified Otherwise TypeError would be raised. Follows up d1901c4c8ec0.

localrepo: experimental support for non-zlib revlog compression The final part of integrating the compression manager APIs into revlog storage is the plumbing for repositories to advertise they are using non-zlib storage and for revlogs to instantiate a non-zlib compression engine. The main intent of the compression manager work was to zstd all of the things. Adding zstd to revlogs has proved to be more involved than other places because revlogs are... special. Very small inputs and the use of delta chains (which are themselves a form of compression) are a completely different use case from streaming compression, which bundles and the wire protocol employ. I've conducted numerous experiments with zstd in revlogs and have yet to formalize compression settings and a storage architecture that I'm confident I won't regret later. In other words, I'm not yet ready to commit to a new mechanism for using zstd - or any other compression format - in revlogs. That being said, having some support for zstd (and other compression formats) in revlogs in core is beneficial. It can allow others to conduct experiments. This patch introduces *highly experimental* support for non-zlib compression formats in revlogs. Introduced is a config option to control which compression engine to use. Also introduced is a namespace of "exp-compression-*" requirements to denote support for non-zlib compression in revlogs. I've prefixed the namespace with "exp-" (short for "experimental") because I'm not confident of the requirements "schema" and in no way want to give the illusion of supporting these requirements in the future. I fully intend to drop support for these requirements once we figure out what we're doing with zstd in revlogs. A good portion of the patch is teaching the requirements system about registered compression engines and passing the requested compression engine as an opener option so revlogs can instantiate the proper compression engine for new operations. That's a verbose way of saying "we can now use zstd in revlogs!" On an `hg pull` conversion of the mozilla-unified repo with no extra redelta settings (like aggressivemergedeltas), we can see the impact of zstd vs zlib in revlogs: $ hg perfrevlogchunks -c ! chunk ! wall 2.032052 comb 2.040000 user 1.990000 sys 0.050000 (best of 5) ! wall 1.866360 comb 1.860000 user 1.820000 sys 0.040000 (best of 6) ! chunk batch ! wall 1.877261 comb 1.870000 user 1.860000 sys 0.010000 (best of 6) ! wall 1.705410 comb 1.710000 user 1.690000 sys 0.020000 (best of 6) $ hg perfrevlogchunks -m ! chunk ! wall 2.721427 comb 2.720000 user 2.640000 sys 0.080000 (best of 4) ! wall 2.035076 comb 2.030000 user 1.950000 sys 0.080000 (best of 5) ! chunk batch ! wall 2.614561 comb 2.620000 user 2.580000 sys 0.040000 (best of 4) ! wall 1.910252 comb 1.910000 user 1.880000 sys 0.030000 (best of 6) $ hg perfrevlog -c -d 1 ! wall 4.812885 comb 4.820000 user 4.800000 sys 0.020000 (best of 3) ! wall 4.699621 comb 4.710000 user 4.700000 sys 0.010000 (best of 3) $ hg perfrevlog -m -d 1000 ! wall 34.252800 comb 34.250000 user 33.730000 sys 0.520000 (best of 3) ! wall 24.094999 comb 24.090000 user 23.320000 sys 0.770000 (best of 3) Only modest wins for the changelog. But manifest reading is significantly faster. What's going on? One reason might be data volume. zstd decompresses faster. So given more bytes, it will put more distance between it and zlib. Another reason is size. In the current design, zstd revlogs are *larger*: debugcreatestreamclonebundle (size in bytes) zlib: 1,638,852,492 zstd: 1,680,601,332 I haven't investigated this fully, but I reckon a significant cause of larger revlogs is that the zstd frame/header has more bytes than zlib's. For very small inputs or data that doesn't compress well, we'll tend to store more uncompressed chunks than with zlib (because the compressed size isn't smaller than original). This will make revlog reading faster because it is doing less decompression. Moving on to bundle performance: $ hg bundle -a -t none-v2 (total CPU time) zlib: 102.79s zstd: 97.75s So, marginal CPU decrease for reading all chunks in all revlogs (this is somewhat disappointing). $ hg bundle -a -t <engine>-v2 (total CPU time) zlib: 191.59s zstd: 115.36s This last test effectively measures the difference between zlib->zlib and zstd->zstd for revlogs to bundle. This is a rough approximation of what a server does during `hg clone`. There are some promising results for zstd. But not enough for me to feel comfortable advertising it to users. We'll get there...

revlog: use compression engine APIs for decompression Now that compression engines declare their header in revlog chunks and can decompress revlog chunks, we refactor revlog.decompress() to use them. Making full use of the property that revlog compressor objects are reusable, revlog instances now maintain a dict mapping an engine's revlog header to a compressor object. This is not only a performance optimization for engines where compressor object reuse can result in better performance, but it also serves as a cache of header values so we don't need to perform redundant lookups against the compression engine manager. (Yes, I measured and the overhead of a function call versus a dict lookup was observed.) Replacing the previous inline lookup table with a dict lookup was measured to make chunk reading ~2.5% slower on changelogs and ~4.5% slower on manifests. So, the inline lookup table has been mostly preserved so we don't lose performance. This is unfortunate. But many decompression operations complete in microseconds, so Python attribute lookup, dict lookup, and function calls do matter. The impact of this change on mozilla-unified is as follows: $ hg perfrevlogchunks -c ! chunk ! wall 1.953663 comb 1.950000 user 1.920000 sys 0.030000 (best of 6) ! wall 1.946000 comb 1.940000 user 1.910000 sys 0.030000 (best of 6) ! chunk batch ! wall 1.791075 comb 1.800000 user 1.760000 sys 0.040000 (best of 6) ! wall 1.785690 comb 1.770000 user 1.750000 sys 0.020000 (best of 6) $ hg perfrevlogchunks -m ! chunk ! wall 2.587262 comb 2.580000 user 2.550000 sys 0.030000 (best of 4) ! wall 2.616330 comb 2.610000 user 2.560000 sys 0.050000 (best of 4) ! chunk batch ! wall 2.427092 comb 2.420000 user 2.400000 sys 0.020000 (best of 5) ! wall 2.462061 comb 2.460000 user 2.400000 sys 0.060000 (best of 4) Changelog chunk reading is slightly faster but manifest reading is slower. What gives? On this repo, 99.85% of changelog entries are zlib compressed (the 'x' header). On the manifest, 67.5% are zlib and 32.4% are '\0'. This patch swapped the test order of 'x' and '\0' so now 'x' is tested first. This makes changelogs faster since they almost always hit the first branch. This makes a significant percentage of manifest '\0' chunks slower because that code path now performs an extra test. Yes, I too can't believe we're able to measure the impact of an if..elif with simple string compares. I reckon this code would benefit from being written in C...

hgweb: build the "entries" list directly in filelog command There's no apparent reason to have this "entries" generator function that builds a list and then yields its elements in reverse order and which is only called to build the "entries" list. So just build the list directly, in reverse order. Adjust "parity" generator's offset to keep rendering the same.

convert: remove "replacecommitter" action As pointed out by Yuya, this action doesn't add much (any?) value.

ui: check EOF of getpass() response read from command-server channel readline() returns '' only when EOF is encountered, in which case, Python's getpass() raises EOFError. We should do the same to abort the session as "response expected." This bug was reported to https://bitbucket.org/tortoisehg/thg/issues/4659/

convert: config option to control Git committer actions When converting a Git repository to Mercurial at Mozilla, I encountered a scenario where I didn't want `hg convert` to automatically add the "committer: <committer>" line to commit messages. While I can hack around this by rewriting the Git commit before it is fed into `hg convert`, I figured it would be a useful knob to control. This patch introduces a config option that allows lots of control over the committer value. I initially implemented this as a single boolean flag to control whether to save the committer message. But then there was feedback that it would be useful to save the committer in extra data. While this patch doesn't implement support for saving in extra data, it does add a mechanism for extending which actions to take on the committer field. We should be able to easily add actions to save in extra data. Some of the implemented features weren't asked for. But I figured they could be useful. If nothing else they demonstrate the extensibility of this mechanism.