tests: stabilize test-blackbox.t on Windows I didn't look into why the error is more detailed, but that seems like it's a good thing (other than for recording tests).

tests: stabilize for recent wcache changes This goes with 47e3f554df35::d5622dfe4ba3. I'm not sure if it was really expected that there would be no wcache directory if neither execbit nor symlink is supported.

extdiff: avoid double backslashes in the displayed tool path on Windows This shows the tool path in the help, and changed in 67b180c0e263. uirepr() already does the same thing, but that undoes the mangling in its call to repr().

contrib: add a helper script that help to build interesting repositories The script is dedicated to building a couple of repositories that should be interesting to run discovery from one another. It seems a common enough need to contribute it upstream.

py3: listify filter() to call len() on it Differential Revision: https://phab.mercurial-scm.org/D5354

rebase: fix dir/file conflict detection when using in-mem merge Differential Revision: https://phab.mercurial-scm.org/D5360

tests: show that in-mem rebase does not find path dir/file conflicts Differential Revision: https://phab.mercurial-scm.org/D5359

extdiff: register the configuration generated commands with a help category Otherwise, 'extdiff' shows up under file management and the rest of the commands are at the bottom under 'Uncategorized'.

loggingutil: document openlogfile() This function will be used later for command-server logging.

loggingutil: extract openlogfile() and proxylogger to new module This module isn't placed under the "utils" package since it needs "ui" to process things. It's called "loggingutil", not "logutil" because the word "log" is too obscure in our codebase.

blackbox: pass in options to _openlogfile() as arguments This prepares for extracting utility function from the blackbox module.

blackbox: just try writing to repo.vfs and update lastlogger on success This is simpler and more robust. Before, an empty ".hg" directory would be created if it's removed after checking vfs.isdir('.').

vfs: add option to not create parent directories implicitly In blackbox, we don't want to create a ".hg" directory by mistake. This provides a race-safe option to achieve that.

repo: add a `wcachevfs` to access the `.hg/wcache/` directory This wvfs will allow us to migrate various cache to the new `wcache` directory. Helping with cache issues with "share".

cache: create `wcache` directory at init time The cache directory will be needed very quickly, so it seems simpler to create it early to make sure it has the same owner and permission than the other directory in the repository.

cache: create `cache` directory at init time The cache directory will be needed very quickly, so it seems simpler to create it early to make sure it has the same owner and permission than the other directory in the repository.

check-exec: write file in 'wcache' instead of 'cache' Some cache are relevant or affected by the working copy used. So the `.hg/cache` directory is not the best place for them because multiple shared repository can end up fighting over them. To address this issue, we introduce a new 'wcache' directory to host this kind of cache. The first user are the `checkisexec` type file. These files describe property of the working copy and fit the use-case well.

rebase: abort in-mem rebase if there's a dirty merge state In-memory merge uses the on-disk merge state, so we should not allow it run in-memory merge when the merge state is not clean. We should probably not use the on-disk merge state when running in-memory merge, but chaning that is not suitable for the stable branch. Differential Revision: https://phab.mercurial-scm.org/D5357

rebase: preserve working copy when redoing in-mem rebase on disk When in-memory rebase runs into conflicts, we retry it on disk. But before we do that, we abort the in-memory rebase. That is done because even though it's mostly in memory, there are still a few state files written (e.g. the merge state). We should make it not write those files so we don't need to abort, but for the stable branch, let's explicitly clear the state we need to clear instead of running the usual abort code. Differential Revision: https://phab.mercurial-scm.org/D5356

tests: show that in-mem rebase falling back loses state Both working copy changes and the merge state is lost when in-memory rebase falls back to on-disk mode. Differential Revision: https://phab.mercurial-scm.org/D5355

commandserver: get around ETIMEDOUT raised by selectors2 selector.select() should exits with an empty event list on timed out, but selectors2 raises OSError if timeout expires while recovering from EINTR. Spotted while debugging new chg feature.

selectors2: backport minimal fix of timeout handling from 2.0.1 The original code would raise TypeError since OSError() doesn't support keyword arguments. We can't simply import the selectors 2.0.1, which still spawns "uname -p" through platform.system(). We could switch to the unreleased version, but I decided to not right now to minimize the change.

mmapindex: set default to 1MB mmapping index is more efficient if we only need a small part of it. The 1MB value has been picked arbitrarily, a lower value might be better. On a large repository with a 60MB index, we see the following performance gain: hg perfindex before: ! wall 0.032023 comb 0.040000 user 0.000000 sys 0.040000 (best of 100) after: ! wall 0.000196 comb 0.000000 user 0.000000 sys 0.000000 (best of 1060) The speed boost benefit all cases, including the one where the full index needs to be parsed. hg perfindex --rev 0 before: ! wall 0.040673 comb 0.030000 user 0.000000 sys 0.030000 (best of 100) after ! wall 0.010713 comb 0.020000 user 0.010000 sys 0.010000 (best of 212) This gain reflect in higher level operation: hg perfbookmarks --clear-revlogs before: ! wall 0.161339 comb 0.160000 user 0.130000 sys 0.030000 (best of 56) after: ! wall 0.123228 comb 0.120000 user 0.120000 sys 0.000000 (best of 68)

mmapindex: move the 'mmapindexthreshold' option out of experimental The option is useful and should be advertised more. We move it out of experimental as a first step. The `storage` section is selected as this is related to how the storage is accessed. A new 'performance' section might be more appropriate. We move from 'mmapindexthreshold` to `mmap-threshold` as non-index item are also suitable for mmap (eg: the rev-branch-cache). If relevant, we can introduce sub-option `mmap-threshold.revlog-index` later.

perf: add a --rev attribute to perfindex This allow for benchmarking the time necessary to look for other version than the tip.

perf: update perfindex to be more realistic The previous code was creating a revlog manually, we now use the actual `localrepo` method to create it. We have to jump though extra hops to work around the impact of filecache.

match: drop unnecessary wrapping of regex in group It seems the regexes have been wrapped in an unnamed group since b6c42714d900 (Add locate command., 2005-07-05). In that commit, the grouping was needed because there was a "head" ('^') added before the group and a "tail" (os.sep) added after it. It seems the head was moved inside the group in 1c0c413cccdd (Get add and locate to use new repo and dirstate walk code., 2005-07-18) and the tail was moved inside the group in 89985a1b3427 (Clean up walk and changes code to use normalised names properly., 2005-07-31), So it seems to me that we've carried around the unnecessary group for 13 years. This patch removes it. Differential Revision: https://phab.mercurial-scm.org/D5352

match: use _BASE_SIZE instead of magic value 4 Differential Revision: https://phab.mercurial-scm.org/D5351

match: make "groupsize" include the trailing "|" I think this is a little easier to follow and it will simplify later patches too. Differential Revision: https://phab.mercurial-scm.org/D5350

match: fix an unaligned (but harmless) indent Differential Revision: https://phab.mercurial-scm.org/D5349

match: raise an Abort error instead of OverflowError This case of OverflowError (one single pattern being too large) has never been properly caught in the past.

match: avoid translating glob to matcher multiple times for large sets For hgignore with many globs, the resulting regexp might not fit under the 20K length limit. So the patterns need to be broken up in smaller pieces. Before this change, the logic was re-starting the full process from scratch for each smaller pieces, including the translation of globs into regexp. Effectively doing the work over and over. If the 20K limit is reached, we are likely in a case where there is many such glob, so exporting them is especially expensive and we should be careful not to do that work more than once. To work around this, we now translate glob to regexp once and for all. Then, we assemble the resulting individual regexp into valid blocks. This raises a very significant performance win for large `.hgignore file`: Before: ! wall 0.153153 comb 0.150000 user 0.150000 sys 0.000000 (median of 66) After: ! wall 0.059793 comb 0.060000 user 0.060000 sys 0.000000 (median of 100)

match: extract function that group regexps

match: test for overflow error in pattern If a single pattern is too large to handle, we raise an exception. This case is now doctested.

match: extract a literal constant into a symbolic one

tests: apply binary mode to output in seq.py I noticed this when playing with running tests using WSL, and iterating over the output yielded '0\r', '1\r',... Most of the other *.py tools do this, and `seq` on MSYS lacks '\r' in the output, so this is more consistent.

perf: add a `--clear-caches` to `perfbranchmapupdate` This flag will help to measure the time we spend loading various cache that support the branchmap update. Example for an 500 000 revisions repository: hg perfbranchmapupdate --base 'not tip' --target 'tip' ! wall 0.000860 comb 0.000000 user 0.000000 sys 0.000000 (best of 336) hg perfbranchmapupdate --base 'not tip' --target 'tip' --clear-caches ! wall 0.029494 comb 0.030000 user 0.030000 sys 0.000000 (best of 100)

perf: start from an existing branchmap if possible If the --base set if a superset of one of the cached branchmap, we should use as a starting point. This greatly help the overall runtime of `hg perfbranchmapupdate` For example, for a repository with about 500 000 revisions, using this trick make the command runtime move from about 200 second to about 10 seconds. A 20x gain.

perf: rely on repoview for perfbranchmapupdate Using 'repoview' matching the base and target subset make the benchmark more realistic. It also unlocks optimization to make the command initialization faster.

perf: pre-indent some code in `perfbranchmapupdate` This make the next patch easier to read.

perf: add a `perfbranchmapupdate` command This command benchmark the time necessary to update the branchmap between two sets of revisions. This changeset introduce a first version, doing nothing fancy regarding cache or other internal details.

push: config option to control behavior when pushing to a publishing server Pushing to a publishing server by mistake can lead to a difficult situation to solve because evolution doesn't work on public changesets. This new experimental config tries to help avoiding unintentionally (or at least being aware of) pushing to publishing remotes. `hg push --publish` can be used to make push succeed even when auto-publish is set to 'abort'.

narrowcommands: remove an unrequired `repo.narrowpats` call We call that few lines above and do nothing significant in between which can change the narrowpats. So let's use values returned by that call. Differential Revision: https://phab.mercurial-scm.org/D5348

manifest: reject lines shorter than 42 bytes, not 22 Yuya correctly spotted during the review of f27f8e9ef1e73 that we're dealing with hexlified hashes here, and so it should be 42 bytes not 22. Differential Revision: https://phab.mercurial-scm.org/D5347

blackbox: initialize logger with repo instance The blackboxlogger is unusable without a repo. Let's simply initialize it with a repo instance.

blackbox: do not nullify repo to deactivate the logger on failure The _repo will be a mandatory attribute. Instead, make the logger to not track any events.

blackbox: extract global last logger to proxylogger class So the blackboxlogger can be instantiated with a repo.

ui: pass in bytes opts dict to logger.log() This is the convention of the Mercurial API.

ui: pass in formatted message to logger.log() This makes sure that all logger instances will handle the message arguments properly.

blackbox: send debug message to logger by core ui Since the core ui.log() may recurse into ui.log() through ui.debug(), it must guard against recursion. The ui extension class can finally be removed.

blackbox: change the way of deactivating the logger on write error This prepares for the upcoming code move. The recursion guard will be ported to the core ui.

match: remove obsolete catching of OverflowError Since 0f6a1bdf89fb (match: handle large regexes, 2007-08-19), we catch an OverflowError from the regex engine and split up the regex if that happens. In 59a9dc9562e2 (ignore: split up huge patterns, 2008-02-11), that was extended to raise an OverflowError in our code even if the regex engine doesn't raise it. It's unclear if there was a range of regex sizes where the OverflowError would be raised from the regex engine but that were still below the limit we added in our code. Either way, both limitations were probably removed in Python 2.7.4 when the regex code width was extended from 16bit to 32bit (or Py_UCS4) integer (thanks to Yuya for finding that out). If at least the first limitation was removed, we no longer should be using OverflowError for flow control, so this patch changes that. Differential Revision: https://phab.mercurial-scm.org/D5309

sparse: raise a move verbose index error from the C code If we don't like a value we should print it.

narrow: drop the bundle2 capability since we have server capabilities (BC) This patch drops the narrow bundle2 capabilities since we introduced narrow server capabilities which are more nice and now used everywhere. I am not sure what it can affect, so on safe side I marked this as BC. Also I removed the NARROWCAP constant as that kind of conflicts with the same name constant in wireprototypes.py. Differential Revision: https://phab.mercurial-scm.org/D4892

vfs: extract the audit path logic into a submethod This will make it possible to apply it in more cases.

subrepo-git: use an official origvfs when appropriate The origvfs has the auditor properly set and can move file without issue. The current code is currently working without errors because rename are not audited, yet.

revert: extract origvfs logic in a sub-function The subrepo's "revert" logic could benefit from it.

vfs: treat 'undo.' file the same as 'journal.' file They are the same kind of file, they are protected by the store lock, but directly lives inside the '.hg' directory. No warnings were ever raised about them because `vfs.rename` is not audited. Something we are trying to change.

perf: add a perfignore command The command is meant to benchmark operations related to hgignore. Right now the command is benchmarking the loading time of the hgignore rules.

py3: use pycompat.xrange instead of xrange xrange does not exists on Python 3. Differential Revision: https://phab.mercurial-scm.org/D5302

store: write fncache only once if there are both adds and removes Differential Revision: https://phab.mercurial-scm.org/D5307

perf: disable revlogs clearing in `perftags` by default This aligns things with what `perfbookmarks` does. I decided to disable the revlogs clearing by default to focus on the core logic by default, ignoring side effects. If we prefer to emphasize the side effect, we can instead keep this on in `perftags` and enable it by default in `perfbookmarks`.

perf: add a `clear-revlogs` flag to `perfbookmarks` This flag (off by default) makes it possible to enable the refresh of the changelog and revlog. This is useful to check for costly side effects of bookmark loading. Usually, these side effects are shared with other logics (eg: tags). example output in my mercurial repo (with 1 bookmark, so not a great example): $ hg perfbookmarks ! wall 0.000044 $ hg perfbookmarks --clear-revlogs ! wall 0.001380

tags: cache `repo.changelog` access when checking tags nodes The tags reading process checks if the nodes referenced in tags exist. Caching the access to `repo.changelog` provides a large speedup for repositories with many tags. running `hg perftags` in a large private repository before: ! wall 0.393464 comb 0.390000 user 0.330000 sys 0.060000 (median of 25) after: ! wall 0.267711 comb 0.270000 user 0.210000 sys 0.060000 (median of 38)

perf: add a `clear-revlogs` flag to `perftags` This flag (on by default) makes it possible to disable the refresh of the changelog and revlog. This is useful to check for the time spent in the core tags logic without the associated side effects. Usually, these side effects are shared with other logics (eg: bookmarks). Example output in my Mercurial repository $ hg perftags ! wall 0.017919 comb 0.020000 user 0.020000 sys 0.000000 (best of 141) $ hg perftags --no-clear-revlogs ! wall 0.012982 comb 0.010000 user 0.010000 sys 0.000000 (best of 207)

perf: stop creating new revlog by hand in perftags It's better to let the repository logic create its own object. We now just clear the cache. New object will be automatically created from there.

revlog: update the documentation for `trim_endidx` The function role drifted since the function was commented.

revlog: properly detect corrupted revlog in `index_get_length` Pointed out by Yuya Nishihara.

perf: rename `perfhelper-tracecopies` to `perfhelper-pathcopies` The command it supports is called `perfpathcopies`. It seems better to align the names.

perf: add a docstring to `perfpathcopies` This will help people to find this command.

revlog: update the docstring of `ancestors` to match reality Code using this method expect the revision to be (reverse) sorted. As pointed by Yuya Nishihara, the docstring should reflect that.

remotefilelog: fix typo in docstring Differential Revision: https://phab.mercurial-scm.org/D5306

store: append to fncache if there are only new files to write Before this patch, if we have to add a new entry to fncache, we write the whole fncache again which slows things down on large fncache which have millions of entries. Addition of a new entry is common operation while pulling new files or commiting a new file. This patch adds a new fncache.addls set which keeps track of the additions happening and store them. When we write the fncache, we will just read the addls set and append those entries at the end of fncache. We make sure that the entries are new entries by loading the fncache and making sure entry does not exists there. In future if we can check if an entry is new without loading the fncache, that will speed up things more. Performance numbers for commiting a new file: mercurial repo before: 0.08784651756286621 after: 0.08474504947662354 mozilla-central before: 1.83314049243927 after: 1.7054164409637451 netbeans before: 0.7953150272369385 after: 0.7202838659286499 pypy before: 0.17805707454681396 after: 0.13431048393249512 In our internal repo, the performance improvement is in seconds. I have used octobus's ASV perf benchmark thing to get the above numbers. I also see some minute perf improvements related to creating a new commit without a new file, but I believe that's just some noise. Differential Revision: https://phab.mercurial-scm.org/D5301

py3: fix couple of division operator to do integer divison Differential Revision: https://phab.mercurial-scm.org/D5305

py3: use dict.items() instead of dict.iteritems() dict.iteritems() does not exist on Python 3. Differential Revision: https://phab.mercurial-scm.org/D5304

py3: convert strings to bytes in tests/test-remotefilelog-histpack.py Differential Revision: https://phab.mercurial-scm.org/D5303

py3: replace str() with pycompat.bytestr() or ('%d' % int) After this patch, test-fastannotate-diffopts.t is about to pass. There are some extra newlines in the output. Differential Revision: https://phab.mercurial-scm.org/D5300

perf: add a `--timing` argument to `perfhelper-tracecopies` The new argument will help picking better pair for benchmarking. See documentation for details.

ui: manage logger instances and event filtering by core ui The setup code in blackbox needs more tweaks since it has lots of black magics. I'll fix them by follow-up patches. To be clear, the goal of this series is to provide a proper way for command server to install its own logger. I need it to debug in-memory repository cache.

extensions: add "uipopulate" hook, called per instance, not per process In short, this is the "reposetup" function for ui. It allows us to modify ui attributes without extending ui.__class__. Before, the only way to do that was to abuse the config dictionary, which is copied across ui instances. See the next patch for usage example.

hgweb: load globally-enabled extensions explicitly Before, extensions were loaded as a side effect of hg.repository() if the hgweb was executed as a CGI/WSGI. I want to make it explicit so that another ui hook can be inserted after extensions.loadall().

tests: sniff for libfuzzer actually being available in test-fuzz-targets.t When I upgraded the FreeBSD buildbot to 11.2 it seems we picked up clang6, but the default clang on FreeBSD doesn't include libfuzzer. I can't find a way to sniff for libfuzzer without running a compile, so here we are. Differential Revision: https://phab.mercurial-scm.org/D5270

tests: sniff for /usr/local/bin/gmake and use it in test-fuzz-targets.t This isn't as robust as it probably should be, but for now it'll get the job done on the buildbots. Differential Revision: https://phab.mercurial-scm.org/D5269

tests: stabilize test-inherit-mode.t on FreeBSD and macOS (issue6026) Symbolic links are funny permissions-wise, but on the linked issue Yuya has convinced me that we can ignore this permissions issue on macOS (FreeBSD allows setting permissions bits but ignores them) and we'll be in fine shape.

wireprotov2peer: wait for initial object before resolving future As part of rolling out wireprotov2 with redirect support, I encountered an edge case with regards to future resolution. Essentially, the initial response frame from the server did not fully decode the initial CBOR object. The frame wasn't marked as EOS. In the previous code, we resolved the future for the request to response.objects(), which mapped to the commandresponse instance which would eventually produce a redirect. Upon receiving subsequent data, the initial CBOR object containing the redirect would be decoded and we'd process the redirect. However, the future would already have been resolved with the initial commandresponse.objects() and the client iterating over the objects wouldn't receive any objects from the redirect because the redirect was populating a different commandresponse instance! This commit changes the logic so we don't resolve futures until the initial CBOR response object is fully decoded or until EOS occurs. In cases where there is an empty or partial frame associated with a redirect, the future will now resolve with the commandresponse containing the proper series of decoded objects.

wireprotov2peer: always return a bool from _processredirect() Without this, we may stop servicing the redirect response if the future has already been resolved. And the future will often be resolved very early, since many consumers iterate the decoded CBOR object stream and expect data to lazily arrive.

tests: disable remotefilelog on Windows I've spent a non trivial amount of time trying to eliminate the test errors, but it's looking like this is pretty dependent on Unix support. For example, there are attempts to delete open files, and uses of threads that report I/O attempts on closed files. (Maybe this is a race condition? Don't we usually use processes as workers on Windows?) In any event, I don't want real new errors elsewhere to be masked by these known problems. For some reason $CACHEDIR is reported as missing in test-remotefilelog-repack.t, but it actually exists in the hgcloneshallow call inside shallowutil.mkstickygroupdir(). By the time the process exits, it's gone. I don't see it being removed by code that calls 'rmdir' or 'remove' in the extension itself.

perf: run 'setup' function during stub run The benchmarked function might need the content of the setup to be run in order to function properly.

perf: fallback to subset if ondisk cache is missing in perfbranchmapload If there is no branchmap on disk for that filter, it means that the cache from some subset's filter is relevant for this one. We look for it instead of aborting. That way it is much simpler to run the command in an automated way. We can now add it to `test-contrib-perf.t`.

perf: prewarm the branchmap in perfbranchmapload It is not very interesting to have the command randomly failing because the branchmap for the tested filter happens to be cold. So we make sure to have a valid up to date branchmap before going further. The data might still be missing from disk if a subset was equivalent. See next changeset for details and fix.

localrepo: correct docstring of filectx() The same reason as b6c2543e1dd8. It can't be any changeset specifiers but revision number.

annotate: remove dead code to not convert path to relative path It's annotate. There should be at least one file path specified.

annotate: start pager soon after command options are validated It helps extracting helper class.

annotate: check and update command options first It helps extracting helper class.

annotate: format local tables in less-dense form I'll move these to a class, where one-extra indent will be needed.

perf: rename version flag of perfchangegroupchangelog to cgversion The version flag conflicts with the global version flag and does not work. Differential Revision: https://phab.mercurial-scm.org/D5297 Differential Revision: https://phab.mercurial-scm.org/D5298

procutil: don't allow the main 'hg' script to be treated as the Windows exe Previously, there were a handful of errors like this: $ hg prefetch --repack (running background incremental repack) + abort: %1 is not a valid Win32 application + [255] CreateProcess() doesn't append .exe when `lpApplicationName` contains a path, and a python script isn't directly executable.

remotefilelog: drop some compatibility cruft for finding the hg exeutable

branchmap: build the revbranchcache._namesreverse() only when required On big repositories with a lot of named branches and that also increasing over time, building of this dict can be expensive and shows up in profile. For our internal repository, this saves ~0.05 seconds. Thanks to Yuya for suggesting using util.propertycache() and util.clearcachedproperty(). Differential Revision: https://phab.mercurial-scm.org/D5291

sparse-revlog: put the native implementation of slicechunktodensity to use When possible, the C implementation of delta chain slicing will be used. providing a large boost in performance for this operation. To take a practical example of restoring manifest revision '59547c40bc4c' for a reference NetBeans repository (using sparse-revlog). The media time of the step `slice-sparse-chain` of `perfrevlogrevision` improve from 0.660 ms to 0.098 ms; The full series move delta chain slicing from 1.120 ms to 0.098 ms; Implementing _slicechunktosize into C would yield further improvements. However, the performance seems good enough for now.

cext: increment the `parsers` module version We introduced a new `slicechunktodensity` method to the index.

sparse-revlog: introduce native (C) implementation of slicechunktodensity This is a C implementation of `_slicechunktodensity` in the `mercurial/revlogutils/deltas.py` file. The algorithm involves a lot of integer manipulation and low-level access to index data. Having a C implementation of it raises a large performance improvement. See later changeset in this series for details.

sparse-revlog: add a `trim_endidx` function in C We are about to implement a native version of `slicechunktodensity`. For clarity, we introduce the helper functions first. This function implement a subpart of the python function `_trimchunk` in `mercurial/revlogutils/deltas.py`. Handling of actual Python objects is left to the caller function.

sparse-revlog: add a `index_segment_span` function in C We are about to implement a native version of `slicechunktodensity`. For clarity, we introduce the helper functions first. This new function provides an efficient way to retrieve some of the information needed by `slicechunktodensity`.

sparse-revlog: add a `index_get_length` function in C We are about to implement a native version of `slicechunktodensity`. For clarity, we introduce the helper functions first. This new function provides an efficient way to retrieve some of the information needed by `slicechunktodensity`.

sparse-revlog: add a `index_get_start` function in C We are about to implement a native version of `slicechunktodensity`. For clarity, we introduce the helper functions first. This new function provides an efficient way to retrieve some of the information needed by `slicechunktodensity`.

perf: add --clear-revlog flag to branchmapload Having the changelog index already loaded when loading the branchmap can have a large impact on performance. Example runs (large private repository): hg perfbranchmapload -f base ! wall 0.116722 comb 0.120000 user 0.110000 sys 0.010000 (best of 59) hg perfbranchmapload -f base --clear-revlogs ! wall 0.258246 comb 0.230000 user 0.220000 sys 0.010000 (best of 31)

perf: introduce a function to fully "unload" a changelog The function remove various attributes and caches related to changelog. This is getting a common requirement.

perf: use an explicit function in perfbranchmapload This make things clearer.

perf: update function name to match `perfbranchmapload` command Having function with the same name as the command is simpler.

perf: fix a minor typo in perfbranchmapload

context: floor adjustlinkrev graph walk during copy tracing The `_adjustlinkrev` method gains an optional "stoprev" argument. The linkrev adjustment will give up once this floor is reached. The relevant functions using `_adjustlinkrev` are updated to pass an appropriate value in the copy tracing code. In some private repository, about 10% of the status call triggered the pathological case addressed by this change. The speedup varies from one call to another, the best-observed win is moving from 170s to 11s. The effect of this change can be seen in the public pypy repository, running the following command: hg perftracecopies --source 83c9ff0c0206 --destination 59c79103d5b0 before: 3.401753 seconds after: 2.634897 seconds (-23%)

context: small refactoring of `isintroducedafter` This make the next change clearer.

context: split `introrev` logic in a sub function We want to add a mechanism to stop iteration early associated to intro rev early in some case. However, it does not make sense to expose it in the public `filectx` API. So we split the code into an internal method instead.

context: introduce an `isintroducedafter` method and use it in copies Right now, copy tracing make effort to not traverse the graph too much to save performance. It uses a "limit" acting as a floor revision past which data are no longer relevant to the current copy tracing. However, to enforce this limit, it does a call to `filectx.rev()` and that call can trigger a graph traversal on its own. That extra graph traversal is unaware of the current limit and can become very expensive. That cost is increased by the nature of work done in adjust link rev, we are not only walking down the graph, we are also checking the affected file for each revision we walk through. Something significantly more expensive than the walk itself. To work around this we need to make the `filectx` operation aware of the current limit. The first step is to introduce a dedicated method: `isintroducedafter`. We'll then rework that method logic to stop traversal as soon as possible.

context: take advantage of `_descendantrev` in introrev if available Before this changeset, `_descendantrev` was ignored and `introrev` could return a "wrong" result. I was previously fine because there seems to be no existing code using both `introrev` and `_descendantrev` at the same time. However, we would like to change that.

context: spell out the logic around linkrev adjustement starting point We make the intent of the `_changeid` and `_changectx` checks explicit. The same logic was previously performed by the `self.rev()` call. The new code is a bit redundant, but much clearer.

perf: add a new `perfhelper-tracecopies` command The command is not measuring performance itself, it digs interesting statistic to help pick good arguments for the `perfcopytrace` command.

narrow: extract helper for parsing narrowspec file This will be used for parsing a file that's stored in a different location. Differential Revision: https://phab.mercurial-scm.org/D5277

py3: cast attribute name to sysstr in clearcachedproperty()