verify: don't init subrepo when missing one is referenced (issue5128) (API) Initializing a subrepo when one doesn't exist is the right thing to do when the parent is being updated, but in few other cases. Unfortunately, there isn't enough context in the subrepo module to distinguish this case. This same issue can be caused with other subrepo aware commands, so there is a general issue here beyond the scope of this fix. A simpler attempt I tried was to add an '_updating' boolean to localrepo, and set/clear it around the call to mergemod.update() in hg.updaterepo(). That mostly worked, but doesn't handle the case where archive will clone the subrepo if it is missing. (I vaguely recall that there may be other commands that will clone if needed like this, but certainly not all do. It seems both handy, and a bit surprising for what should be a read only operation. It might be nice if all commands did this consistently, but we probably need Angel's subrepo caching first, to not make a mess of the working directory.) I originally handled 'Exception' in order to pick up the Aborts raised in subrepo.state(), but this turns out to be unnecessary because that is called once and cached by ctx.sub() when iterating the subrepos. It was suggested in the bug discussion to skip looking at the subrepo links unless -S is specified. I don't really like that idea because missing a subrepo or (less likely, but worse) a corrupt .hgsubstate is a problem of the parent repo when checking out a revision. The -S option seems like a better fit for functionality that would recurse into each subrepo and do a full verification. Ultimately, the default value for 'allowcreate' should probably be flipped, but since the default behavior was to allow creation, this is less risky for now.

setup: detect Python DLL filename from loaded DLL Attempting to build Mercurial from source using MinGW from msys2 on Windows produces a hg.exe that attempts to load e.g. python27.dll. MinGW prefixes its library name with "lib" and adds a period between the major and minor versions. e.g. "libpython2.7.dll." Before this patch, hg.exe files in a MinGW environment would either fail to find a Python DLL or would attempt to load a non-MinGW DLL, which would summarily explode. Either way, hg.exe wouldn't work. This patch improves the code that determines the Python DLL filename to actually use the loaded Python DLL instead of inferring it. Basically we take the handle of the loaded DLL from sys.dllhandle and call a Windows API to try to resolve that handle to a filename.

exewrapper: add .dll to LoadLibrary() argument LoadLibrary() changes behavior depending on whether the argument passed to it contains a period. From the MSDN docs: If no file name extension is specified in the lpFileName parameter, the default library extension .dll is appended. However, the file name string can include a trailing point character (.) to indicate that the module name has no extension. When no path is specified, the function searches for loaded modules whose base name matches the base name of the module to be loaded. If the name matches, the load succeeds. Otherwise, the function searches for the file. As the subsequent patch will show, some environments on Windows define their Python library as e.g. "libpython2.7.dll." The existing code would pass "libpython2.7" into LoadLibrary(). It would assume "7" was the file extension and look for a "libpython2.dll" to load. By passing ".dll" into LoadLibrary(), we force it to search for the exact basename we want, even if it contains a period.

update: correct description of --check option The old "update across branches if no uncommitted changes" made it sound like updating across branches (with no uncommitted changes) was allowed only with this option, which was not true. Also, the option did not care whether it was linear or across branches. Instead, it checked that there were no uncommitted changes. Let's explain what it does instead of trying to suggest what happens without it.

util: fix race in makedirs() Update makedirs() to ignore EEXIST in case someone else has already created the directory in question. Previously the ensuredirs() function existed, and was nearly identical to makedirs() except that it fixed this race. Unfortunately ensuredirs() was only used in 3 places, and most code uses the racy makedirs() function. This fixes makedirs() to be non-racy, and replaces calls to ensuredirs() with makedirs(). In particular, mercurial.scmutil.origpath() used the racy makedirs() code, which could cause failures during "hg update" as it tried to create backup directories. This does slightly change the behavior of call sites using ensuredirs(): previously ensuredirs() would throw EEXIST if the path existed but was a regular file instead of a directory. It did this by explicitly checking os.path.isdir() after getting EEXIST. The makedirs() code did not do this and swallowed all EEXIST errors. I kept the makedirs() behavior, since it seemed preferable to avoid the extra stat call in the common case where this directory already exists. If the path does happen to be a file, the caller will almost certainly fail with an ENOTDIR error shortly afterwards anyway. I checked the 3 existing call sites of ensuredirs(), and this seems to be the case for them.

chg: initialize sockdirfd to -1 instead of AT_FDCWD As we don't use sockdirfd yet, this is the simplest workaround to compile chg on old Unices where AT_FDCWD does not exist. Foozy pointed out Mac OS X 10.10 is required for AT_FDCWD as well as xxxat() functions.

bdiff: further restrain potential quadratic performance This causes the longest_match search to limit itself to a window of 30000 lines during search (roughly 1MB), thus avoiding a full O(N*M) search that might occur in repetitive structured inputs. For a particular class of many MB pathological test cases, this generated the following timings: size before after 10x 1.25s 1.24s 100x 57s 33s 1000x >8400s 400s The times on the right quickly become much faster and appear more linear. While windowing means deltas are no longer "optimal", the resulting deltas were within a couple percent of expected size. While we've yet to have a report of a file with the level of repetition necessary to hit this case, some JSON/XML database dump scenario is fairly likely to hit it. This may also slightly improve the average-case performance for deltas of large binaries.

bdiff: balance recursion to avoid quadratic behavior (issue4704) For highly structured files like JSON or XML dumps with large numbers of duplicate lines (eg braces) and isolated matching lines, bdiff could find large numbers of equally good spans. Because it prefers earlier matches, this would result in pathologically unbalance recursion that resulted in quadratic performance. This patch makes it prefer matches closer to the middle that tend to balance recursion. This change improves the speed of a pathological test case from 1100s to 9s. Included is a smaller test that has a roughly 50x safety margin on the performance it accepts. It's likely to fail on pure builds because difflib also has a recursion-balancing problem.

bdiff: deal better with duplicate lines The longest_match code compares all the possible positions in two files to find the best match. Given a pair of sequences, it effectively searches a grid like this: a b b b c . d e . f 0 1 2 3 4 5 6 7 8 9 a 1 - - - - - - - - - b - 2 1 1 - - - - - - b - 1 3 2 - - - - - - b - 1 2 4 - - - - - - . - - - - - 1 - - 1 - Here, the 4 in the middle says "the first four lines of the file match", which it can compute be comparing the fourth lines and then adding one to the result found when comparing the third lines in the entry to the upper left. We generally avoid the quadratic worst case by only looking at lines that match, which is precomputed. We also avoid quadratic storage by only keeping a single column vector and then keeping track of the best match. Unfortunately, this can get us into trouble with the sequences above. Because we want to reuse the '3' value when calculating the '4', we need to be careful not to overwrite it with the '2' we calculate immediately before. If we scan left to right, top to bottom, we're going to have a problem: we'll overwrite our 3 before we use it and calculate a suboptimal best match. To address this, we can either keep two column vectors and swap between them (which significantly complicates bookkeeping), or change our scanning order. If we instead scan from left to right, bottom to top, we'll avoid ever overwriting values we'll need in the future. This unfortunately needs several changes to be made simultaneously: - change the order we build the initial hash chains for the b sequence - change the sentinel values from INT_MAX to -1 - change the visit order in the longest_match inner loop - add a tie-breaker preference for earlier matches This last is needed because we previously had an implicit tie-breaker from our visitation order that our test suite relies on. Later matches can also trigger a bug in the normalization code in diff().

bdiff: fix latent normalization bug This bug is hidden by the current bias towards matches at the beginning of the file. When this bias is tweaked later to address recursion balancing, the normalization code could cause the next block to shrink to a negative length, thus creating invalid delta chunks. We add checks here to disallow that. This bug requires test cases that are an awkwardly large size for the test suite, but is very rapidly picked up by the included torture tester.