bundle2: inline changegroup.readexactly() Profiling reveals this loop is pretty tight. Literally any function call elimination can make a big difference. This commit inlines the relatively trivial changegroup.readexactly() method inside the loop. The results with `hg perfbundleread` on a bundle of the Firefox repo speak for themselves: ! read(8k) ! wall 0.679730 comb 0.680000 user 0.140000 sys 0.540000 (best of 15) ! read(16k) ! wall 0.577228 comb 0.570000 user 0.080000 sys 0.490000 (best of 17) ! read(32k) ! wall 0.516060 comb 0.520000 user 0.040000 sys 0.480000 (best of 20) ! read(128k) ! wall 0.496378 comb 0.490000 user 0.010000 sys 0.480000 (best of 20) ! bundle2 iterparts() ! wall 3.460903 comb 3.460000 user 2.760000 sys 0.700000 (best of 3) ! wall 3.056811 comb 3.050000 user 2.340000 sys 0.710000 (best of 4) ! bundle2 iterparts() seekable ! wall 4.312722 comb 4.310000 user 3.480000 sys 0.830000 (best of 3) ! wall 4.007676 comb 4.000000 user 3.170000 sys 0.830000 (best of 3) ! bundle2 part seek() ! wall 6.754764 comb 6.740000 user 3.970000 sys 2.770000 (best of 3) ! wall 6.267110 comb 6.250000 user 3.480000 sys 2.770000 (best of 3) ! bundle2 part read(8k) ! wall 3.668004 comb 3.660000 user 2.960000 sys 0.700000 (best of 3) ! wall 3.404164 comb 3.400000 user 2.650000 sys 0.750000 (best of 3) ! bundle2 part read(16k) ! wall 3.489196 comb 3.480000 user 2.750000 sys 0.730000 (best of 3) ! wall 3.197972 comb 3.200000 user 2.490000 sys 0.710000 (best of 4) ! bundle2 part read(32k) ! wall 3.388569 comb 3.380000 user 2.640000 sys 0.740000 (best of 3) ! wall 3.060557 comb 3.060000 user 2.340000 sys 0.720000 (best of 4) ! bundle2 part read(128k) ! wall 3.276415 comb 3.270000 user 2.560000 sys 0.710000 (best of 4) ! wall 2.952209 comb 2.950000 user 2.230000 sys 0.720000 (best of 4) Differential Revision: https://phab.mercurial-scm.org/D1392

bundle2: inline debug logging Profiling revealed that repeated calls to indebug() were consuming a fair amount of CPU during bundle2 reading, with most of the time spent in ui.configbool(). Inlining indebug() and avoiding extra attribute lookups speeds things up substantially. Using `hg perfbundleread` with a Firefox bundle: ! read(8k) ! wall 0.679730 comb 0.680000 user 0.140000 sys 0.540000 (best of 15) ! read(16k) ! wall 0.577228 comb 0.570000 user 0.080000 sys 0.490000 (best of 17) ! read(32k) ! wall 0.516060 comb 0.520000 user 0.040000 sys 0.480000 (best of 20) ! read(128k) ! wall 0.496378 comb 0.490000 user 0.010000 sys 0.480000 (best of 20) ! bundle2 iterparts() ! wall 6.983756 comb 6.980000 user 6.220000 sys 0.760000 (best of 3) ! wall 3.460903 comb 3.460000 user 2.760000 sys 0.700000 (best of 3) ! bundle2 iterparts() seekable ! wall 8.132131 comb 8.110000 user 7.160000 sys 0.950000 (best of 3) ! wall 4.312722 comb 4.310000 user 3.480000 sys 0.830000 (best of 3) ! bundle2 part seek() ! wall 10.860942 comb 10.840000 user 7.790000 sys 3.050000 (best of 3) ! wall 6.754764 comb 6.740000 user 3.970000 sys 2.770000 (best of 3) ! bundle2 part read(8k) ! wall 7.258035 comb 7.260000 user 6.470000 sys 0.790000 (best of 3) ! wall 3.668004 comb 3.660000 user 2.960000 sys 0.700000 (best of 3) ! bundle2 part read(16k) ! wall 7.099891 comb 7.080000 user 6.310000 sys 0.770000 (best of 3) ! wall 3.489196 comb 3.480000 user 2.750000 sys 0.730000 (best of 3) ! bundle2 part read(32k) ! wall 6.964685 comb 6.950000 user 6.130000 sys 0.820000 (best of 3) ! wall 3.388569 comb 3.380000 user 2.640000 sys 0.740000 (best of 3) ! bundle2 part read(128k) ! wall 6.852867 comb 6.850000 user 6.060000 sys 0.790000 (best of 3) ! wall 3.276415 comb 3.270000 user 2.560000 sys 0.710000 (best of 4) Differential Revision: https://phab.mercurial-scm.org/D1391

bundle2: don't use seekable bundle2 parts by default (issue5691) The last commit removed the last use of the bundle2 part seek() API in the generic bundle2 part iteration code. This means we can now switch to using unseekable bundle2 parts by default and have the special consumers that actually need the behavior request it. This commit changes unbundle20.iterparts() to expose non-seekable unbundlepart instances by default. If seekable parts are needed, callers can pass "seekable=True." The bundlerepo class needs seekable parts, so it does this. The interrupt handler is also changed to use a regular unbundlepart. So, by default, all consumers except bundlerepo will see unseekable parts. Because the behavior of the iterparts() benchmark changed, we add a variation to test seekable parts vs unseekable parts. And because parts no longer have seek() unless "seekable=True," we update the "part seek" benchmark. Speaking of benchmarks, this change has the following impact to `hg perfbundleread` on an uncompressed bundle of the Firefox repo (6,070,036,163 bytes): ! read(8k) ! wall 0.722709 comb 0.720000 user 0.150000 sys 0.570000 (best of 14) ! read(16k) ! wall 0.602208 comb 0.590000 user 0.080000 sys 0.510000 (best of 17) ! read(32k) ! wall 0.554018 comb 0.560000 user 0.050000 sys 0.510000 (best of 18) ! read(128k) ! wall 0.520086 comb 0.530000 user 0.020000 sys 0.510000 (best of 20) ! bundle2 forwardchunks() ! wall 2.996329 comb 3.000000 user 2.300000 sys 0.700000 (best of 4) ! bundle2 iterparts() ! wall 8.070791 comb 8.060000 user 7.180000 sys 0.880000 (best of 3) ! wall 6.983756 comb 6.980000 user 6.220000 sys 0.760000 (best of 3) ! bundle2 iterparts() seekable ! wall 8.132131 comb 8.110000 user 7.160000 sys 0.950000 (best of 3) ! bundle2 part seek() ! wall 10.370142 comb 10.350000 user 7.430000 sys 2.920000 (best of 3) ! wall 10.860942 comb 10.840000 user 7.790000 sys 3.050000 (best of 3) ! bundle2 part read(8k) ! wall 8.599892 comb 8.580000 user 7.720000 sys 0.860000 (best of 3) ! wall 7.258035 comb 7.260000 user 6.470000 sys 0.790000 (best of 3) ! bundle2 part read(16k) ! wall 8.265361 comb 8.250000 user 7.360000 sys 0.890000 (best of 3) ! wall 7.099891 comb 7.080000 user 6.310000 sys 0.770000 (best of 3) ! bundle2 part read(32k) ! wall 8.290308 comb 8.280000 user 7.330000 sys 0.950000 (best of 3) ! wall 6.964685 comb 6.950000 user 6.130000 sys 0.820000 (best of 3) ! bundle2 part read(128k) ! wall 8.204900 comb 8.150000 user 7.210000 sys 0.940000 (best of 3) ! wall 6.852867 comb 6.850000 user 6.060000 sys 0.790000 (best of 3) The significant speedup is due to not incurring the overhead to track payload offset data. Of course, this overhead is proportional to bundle2 part size. So a multiple gigabyte changegroup part is on the extreme side of the spectrum for real-world impact. In addition to the CPU efficiency wins, not tracking offset data also means not using memory to hold that data. Using a bundle based on the example BSD repository in issue 5691, this change has a drastic impact to memory usage during `hg unbundle` (`hg clone` would behave similarly). Before, memory usage incrementally increased for the duration of bundle processing. In other words, as we advanced through the changegroup and bundle2 part, we kept allocating more memory to hold offset data. After this change, we still increase memory during changegroup application. But the rate of increase is significantly slower. (A bulk of the remaining gradual increase appears to be the storing of revlog sizes in the transaction object to facilitate rollback.) The RSS at the end of filelog application is as follows: Before: ~752 MB After: ~567 MB So, we were storing ~185 MB of offset data that we never even used. Talk about wasteful! .. api:: bundle2 parts are no longer seekable by default. .. perf:: bundle2 read I/O throughput significantly increased. .. perf:: Significant memory use reductions when reading from bundle2 bundles. On the BSD repository, peak RSS during changegroup application decreased by ~185 MB from ~752 MB to ~567 MB. Differential Revision: https://phab.mercurial-scm.org/D1390

bundle2: only seek to beginning of part in bundlerepo For reasons still not yet fully understood by me, bundlerepo requires its changegroup bundle2 part to be seeked to beginning after part iteration. As far as I can tell, it is the only bundle2 part consumer that relies on this behavior. This seeking was performed in the generic iterparts() API. Again, I don't fully understand why it was here and not in bundlerepo. Probably historical reasons. What I do know is that all other bundle2 part consumers don't need this special behavior (assuming the tests are comprehensive). So, we move the code from bundle2's iterparts() to bundlerepo's consumption of iterparts(). Differential Revision: https://phab.mercurial-scm.org/D1389

bundle2: implement consume() API on unbundlepart We want bundle parts to not be seekable by default. That means eliminating the generic seek() method. A common pattern in bundle2.py is to seek to the end of the part data. This is mainly used by the part iteration code to ensure the underlying stream is advanced to the next bundle part. In this commit, we establish a dedicated API for consuming a bundle2 part data. We switch users of seek() to it. The old implementation of seek(0, os.SEEK_END) would effectively call self.read(). The new implementation calls self.read(32768) in a loop. The old implementation would therefore assemble a buffer to hold all remaining data being seeked over. For seeking over large bundle parts, this would involve a large allocation and a lot of overhead to collect intermediate data! This overhead can be seen in the results for `hg perfbundleread`: ! bundle2 iterparts() ! wall 10.891305 comb 10.820000 user 7.990000 sys 2.830000 (best of 3) ! wall 8.070791 comb 8.060000 user 7.180000 sys 0.880000 (best of 3) ! bundle2 part seek() ! wall 12.991478 comb 10.390000 user 7.720000 sys 2.670000 (best of 3) ! wall 10.370142 comb 10.350000 user 7.430000 sys 2.920000 (best of 3) Of course, skipping over large payload data isn't likely very common. So I doubt the performance wins will be observed in the wild. Differential Revision: https://phab.mercurial-scm.org/D1388

bundle2: implement generic part payload decoder The previous commit extracted _payloadchunks() to a new derived class. There was still a reference to this method in unbundlepart, making unbundlepart unusable on its own. This commit implements a generic version of a bundle2 part payload decoder, without offset tracking. seekableunbundlepart._payloadchunks() has been refactored to consume it, adding offset tracking like before. We also implement unbundlepart._payloadchunks(), which is a thin wrapper for it. Since we never instantiate unbundlepart directly, this new method is not used. This will be changed in subsequent commits. The new implementation also inlines some simple code from unpackermixin and adds some local variable to prevent extra function calls and attribute lookups. `hg perfbundleread` on an uncompressed Firefox bundle seems to show a minor win: ! bundle2 iterparts() ! wall 12.593258 comb 12.250000 user 8.870000 sys 3.380000 (best of 3) ! wall 10.891305 comb 10.820000 user 7.990000 sys 2.830000 (best of 3) ! bundle2 part seek() ! wall 13.173163 comb 11.100000 user 8.390000 sys 2.710000 (best of 3) ! wall 12.991478 comb 10.390000 user 7.720000 sys 2.670000 (best of 3) ! bundle2 part read(8k) ! wall 9.483612 comb 9.480000 user 8.420000 sys 1.060000 (best of 3) ! wall 8.599892 comb 8.580000 user 7.720000 sys 0.860000 (best of 3) ! bundle2 part read(16k) ! wall 9.159815 comb 9.150000 user 8.220000 sys 0.930000 (best of 3) ! wall 8.265361 comb 8.250000 user 7.360000 sys 0.890000 (best of 3) ! bundle2 part read(32k) ! wall 9.141308 comb 9.130000 user 8.220000 sys 0.910000 (best of 3) ! wall 8.290308 comb 8.280000 user 7.330000 sys 0.950000 (best of 3) ! bundle2 part read(128k) ! wall 8.880587 comb 8.850000 user 7.960000 sys 0.890000 (best of 3) ! wall 8.204900 comb 8.150000 user 7.210000 sys 0.940000 (best of 3) Function call overhead in Python strikes again! Of course, bundle2 decoding CPU overhead is likely small compared to decompression and changegroup application. But every little bit helps. Differential Revision: https://phab.mercurial-scm.org/D1387

bundle2: extract logic for seeking bundle2 part into own class Currently, unbundlepart classes support bi-directional seeking. Most consumers of unbundlepart only ever seek forward - typically as part of moving to the end of the bundle part so they can move on to the next one. But regardless of the actual usage of the part, instances maintain an index mapping offsets within the underlying raw payload to offsets within the decoded payload. Maintaining the mapping of offset data can be expensive in terms of memory use. Furthermore, many bundle2 consumers don't have access to an underlying seekable stream. This includes all compressed bundles. So maintaining offset data when the underlying stream can't be seeked anyway is wasteful. And since many bundle2 streams can't be seeked, it seems like a bad idea to expose a seek API in bundle2 parts by default. If you provide them, people will attempt to use them. Seekable bundle2 parts should be the exception, not the rule. This commit starts the process dividing unbundlepart into 2 classes: a base class that supports linear, one-time reads and a child class that supports bi-directional seeking. In this first commit, we split various methods and attributes out into a new "seekableunbundlepart" class. Previous instantiators of "unbundlepart" now instantiate "seekableunbundlepart." This preserves backwards compatibility. The coupling between the classes is still tight: "unbundlepart" cannot be used on its own. This will be addressed in subsequent commits. Differential Revision: https://phab.mercurial-scm.org/D1386

merge with i18n

i18n-pt_BR: synchronized with cabc840ffdee

perf: add command to benchmark bundle reading Upcoming commits will be refactoring bundle2 I/O code. This commit establishes a `hg perfbundleread` command that measures how long it takes to read a bundle using various mechanisms. As a baseline, here's output from an uncompressed bundle1 bundle of my Firefox repo (7,098,622,890 bytes): ! read(8k) ! wall 0.763481 comb 0.760000 user 0.160000 sys 0.600000 (best of 6) ! read(16k) ! wall 0.644512 comb 0.640000 user 0.110000 sys 0.530000 (best of 16) ! read(32k) ! wall 0.581172 comb 0.590000 user 0.060000 sys 0.530000 (best of 18) ! read(128k) ! wall 0.535183 comb 0.530000 user 0.010000 sys 0.520000 (best of 19) ! cg1 deltaiter() ! wall 0.873500 comb 0.880000 user 0.840000 sys 0.040000 (best of 12) ! cg1 getchunks() ! wall 6.283797 comb 6.270000 user 5.570000 sys 0.700000 (best of 3) ! cg1 read(8k) ! wall 1.097173 comb 1.100000 user 0.400000 sys 0.700000 (best of 10) ! cg1 read(16k) ! wall 0.810750 comb 0.800000 user 0.200000 sys 0.600000 (best of 13) ! cg1 read(32k) ! wall 0.671215 comb 0.670000 user 0.110000 sys 0.560000 (best of 15) ! cg1 read(128k) ! wall 0.597857 comb 0.600000 user 0.020000 sys 0.580000 (best of 15) And from an uncompressed bundle2 bundle (6,070,036,163 bytes): ! read(8k) ! wall 0.676997 comb 0.680000 user 0.160000 sys 0.520000 (best of 15) ! read(16k) ! wall 0.592706 comb 0.590000 user 0.080000 sys 0.510000 (best of 17) ! read(32k) ! wall 0.529395 comb 0.530000 user 0.050000 sys 0.480000 (best of 16) ! read(128k) ! wall 0.491270 comb 0.490000 user 0.010000 sys 0.480000 (best of 19) ! bundle2 forwardchunks() ! wall 2.997131 comb 2.990000 user 2.270000 sys 0.720000 (best of 4) ! bundle2 iterparts() ! wall 12.247197 comb 10.670000 user 8.170000 sys 2.500000 (best of 3) ! bundle2 part seek() ! wall 11.761675 comb 10.500000 user 8.240000 sys 2.260000 (best of 3) ! bundle2 part read(8k) ! wall 9.116163 comb 9.110000 user 8.240000 sys 0.870000 (best of 3) ! bundle2 part read(16k) ! wall 8.984362 comb 8.970000 user 8.110000 sys 0.860000 (best of 3) ! bundle2 part read(32k) ! wall 8.758364 comb 8.740000 user 7.860000 sys 0.880000 (best of 3) ! bundle2 part read(128k) ! wall 8.749040 comb 8.730000 user 7.830000 sys 0.900000 (best of 3) We already see some interesting data. Notably that bundle2 has significant overhead compared to bundle1. This matters for e.g. stream clone bundles, which can be applied at >1Gbps. Differential Revision: https://phab.mercurial-scm.org/D1385

sshpeer: add a configurable hint for the ssh error message Adding a possibility to configure error hint to be shown in the case of problems with SSH. Example of such hint can be "Please see http://company/internalwiki/ssh.html". Test Plan: - Ran hg pull with broken link and verified the output has no hint by default: ``` pulling from ssh://brokenrepository.com//repo remote: ssh: Could not resolve hostname brokenrepository.com: Name or service not known abort: no suitable response from remote hg! ``` - Run hg pull --config ui.ssherrorhint="Please see http://company/internalwiki/ssh.html": ``` pulling from ssh://brokenrepository.com//repo remote: ssh: Could not resolve hostname brokenrepository.com: Name or service not known abort: no suitable response from remote hg! (Please see http://company/internalwiki/ssh.html) ``` Differential Revision: https://phab.mercurial-scm.org/D1431

docs: add args/returns docs for some cmdutil, context, and registrar functions When writing my first extension, I found it hard to figure out these functions. I figured documenting their inputs/outputs would help future authors who are new to the codebase. Differential Revision: https://phab.mercurial-scm.org/D1440

commands: add value for cmdtype argument for read only commands In the previous release we added an argument `cmdtype` to registrar.command() which is a enum and tells whether the command is read only, recoverable write or unrecoverable write command. This patch add the value of cmdtype argument for commands which are read only. Differential Revision: https://phab.mercurial-scm.org/D1468

error: add InMemoryMergeConflictsError We'll raise this exception in the merge code, and in-memory users like rebase can catch it and retry without IMM. Differential Revision: https://phab.mercurial-scm.org/D1210

lfs: generate a large file by using `python` instead of yes | head yes(1) on some systems (like gcc112) feels compelled to inform you of broken pipes, such as those triggered by head(1). This works around the problem portably.

setup: add hgext.lfs to list of Python packages This is needed for lfs to get installed. Probably could stand to go into an earlier patch, but I just want to get this stuff pushed.

test-lfs: add tests demonstrating the interaction with largefiles Obviously the original series needs to be accepted first, but there are concerns about how well these extensions will play together before proceeding. It looks like the answer is surprisingly well. There are some merge surprises (largefiles seems to combine the choice of "keep tracking as a large/normal file" with taking the content of the large/normal file) and some existing diff weirdness (largefiles diffs the standins, not the large file). Converting the repo to normal files seemlessly transitions to lfs on the fly. I didn't test going the other way, because I'm not sure why anyone would want to do that. I flagged the lack of a repo requirement after converting, because some of the unsubmitted changes I have add a requirement on commit, but this somehow misses the convert case. I flagged an issue where devel-warnings are emitted on convert, which is a separate issue.

test-lfs: cast the flags printed to an int On Windows, the flag values in the subsequent tests were printing with a 'L' suffix.

lfs: register config options I'm not sure at what point we can get rid of the deprecated options, but for the sake of making progress, they are registered too.

lfs: quiesce check-module-import warnings Specifically, 'symbol import follows non-symbol import: mercurial.i18n'

lfs: import the Facebook git-lfs client extension The purpose of this is the same as the built-in largefiles extension- to handle huge files outside of the normal storage system, generally to keep the amount of data cloned to a lower amount. There are several benefits of implementing the git-lfs protocol, instead of using the largefiles extension: - Bitbucket and Github support (and probably wider support in 3rd party hosting sites in general). [1][2] - The number of hg internals monkey patched are several orders of magnitude lower, so it will be easier to reason about and maintain. Future commands will likely just work, without requiring various wrappers. - The "standin" files are only written to the filelog, not the disk. That should avoid weird edge cases where the largefile and standin files get out of sync. [3] It also avoids the occasional printing of the "hidden" standin file in various messages. - Filesets like size() will work, even if the file isn't present. (It always says 41 bytes for largefiles, whether present or not.) The only place that I see where largefiles comes out on top is that it works with `hg serve` for simple sharing, without external infrastructure. Getting lfs-test-server working was a hassle, and took awhile to figure out. Maybe we can do something to make it work in the future. Long term, I expect that this will be highly preferred over largefiles. But if we are to recommend this to largefile users, there are some UI issues to bikeshed. Until they are resolved, I've marked this experimental, and am not putting a pointer to this in the largefiles help. The (non exhaustive) list of issues I've seen so far are: - It isn't sufficient to just enable the largefiles extension- you have to explicitly add a file with --large before it will pay attention to the configured sizes and patterns on future adds. The justification being that once you use it, you're stuck with it. I've seen people confused by this, and haven't liked it myself. But it's also saved me a few times. Should we do something like have a specific enabling config setting that must be set in the local repo config, so that enabling this extension in the user or system hgrc doesn't silently start storing lfs files? - The largefiles extension adds a repo requirement when the first largefile is committed, so that the extension must always be enabled in the future. This extension is not doing that, and since I only enabled it locally to avoid infecting other repos, I got a cryptic error about missing flag processors when I cloned. Is there no repo requirement due to shallow/narrow clone considerations (or other future advanced things)? - In the (small amount of) reading I've done about the git implementation, it seems that the files and sizes are stored in a tracked .gitattributes file. I think a tracked file for this would be extremely useful for consistency across developers, but this kind of touches on the tracked hgrc file proposal a few months back. - The git client can specify file patterns, not just sizes. - The largefiles extension has a cache directory in the local repo, but also a system wide one. We should probably implement a system wide cache too, so that multiple clones don't have to refetch the files from the server. - Jun mentioned other missing features, like SSH authentication, gc, etc. The code corresponds to c0492b73c7ef in hg-experimental. [4] The only tweaks are to load the extension in the tests with 'lfs=' instead of 'lfs=$TESTDIR/../hgext3rd/lfs', change the import in the *.py test to hgext (from hgext3rd), add the 'testedwith' declaration, and mark it experimental for now. The infinite-push, p4fastimport, and remotefilelog tests were left behind. The devel-warnings for unregistered config options are not corrected yet, nor are the import check warnings. [1] https://www.mercurial-scm.org/pipermail/mercurial/2017-November/050699.html [2] https://bitbucket.org/site/master/issues/3843/largefiles-support-bb-3903 [3] https://bz.mercurial-scm.org/show_bug.cgi?id=5738 [4] https://bitbucket.org/facebook/hg-experimental

run-tests: outputdir also has to be changed if $TESTDIR is not $PWD Following a18eef03d879, running run-tests.py from outside tests/ would lead to the creation of .testtimes and test-*.t.err in $PWD instead of $TESTDIR. This patch fixes that and updates the relevant test.

hgweb: use webutil.commonentry() for nodes (but not for jsdata yet) in /graph This makes graphdata() simpler by using existing code that gets common changeset properties for showing in hgweb. graphdata() is a nested function in graph() that prepares entries for /graph view, but there are two different lists of changesets prepared: "jsdata" for JavaScript-rendered graph and "nodes" for everything else. For "jsdata", properties "node", "user", "age" and "desc" are passed through various template filters because we don't have these filters in JavaScript, so the data has to be prepared server-side. But now that commonentry() is used for producing "nodes" list (and it doesn't apply any filters), these filters need to be added to the appropriate templates (only raw at this moment, everything else either doesn't implement graph or uses JavaScript). This is a bit of refactoring that will hopefully simplify future patches. The end result is to have /graph that only renders the actual graph with nodes and vertices in JavaScript, and the rest is done server-side. This way server-side code can focus on showing a list of changesets, which is easy because we already have /log, /shortlog, etc, and JavaScript code can be simplified, making it easier to add obsolescence graph and other features.

hgweb: check changeset's original branch in graphdata() This piece of code checks if a changeset is the tip of its branch, but as can be seen above in the context, "branch" was prepared for being displayed in hgweb by making it unicode and passing it through url.escape. It's better to use the original ctx.branch().