revlog: switch findmissing to use ancestor.missingancestors This also speeds up other commands that use findmissing, like incoming and merge --preview. With a large linear repository (>400000 commits) and with one incoming changeset, incoming is sped up from around 4-4.5 seconds to under 3.

ancestor: faster algorithm for difference of ancestor sets One of the major reasons rebase is slow in large repositories is the computation of the detach set: the set of ancestors of the changesets to rebase not in the destination parent. This is currently done via a revset that does two walks all the way to the root of the DAG. Instead of doing that, to find ancestors of a set <revs> not in another set <common> we walk up the tree in reverse revision number order, maintaining sets of nodes visited from <revs>, <common> or both. For the common case where the sets are close both topologically and in revision number (relative to repository size), this has been found to speed up rebase by around 15-20%. When the nodes are farther apart and the DAG is highly branching, it is harder to say which would win. Here's how long computing the detach set takes in a linear repository with over 400000 changesets, rebasing near tip: Rebasing across 4 changesets Revset method: 2.2s New algorithm: 0.00015s Rebasing across 250 changesets Revset method: 2.2s New algorithm: 0.00069s Rebasing across 10000 changesets Revset method: 2.4s New algorithm: 0.019s

bisect: add example for limiting bisection to specified directories The bisect command does not have an option to limit itself only to subdirectories, but it's possible to use revsets for the --skip option for the same effect. Given the relative obscurity of revsets, it helps to have this as another example for bisect.

subrepo: use posixpath when diffing, for consistent paths This fixes a Windows failure in test-subrepo-recursion.t introduced by c84ef0047a94.

run-tests: fix an unnoticed check-code violation

run-tests: add a --compiler option Without this option, it is not possible to run the test suite on Windows using mingw's gcc as the compiler.

run-tests: make build command line less intimidating Use a dict for parameters to the format string, instead of a ridiculous number of positional parameters.

hooks: be even more forgiven of non-fd descriptors (issue3711) Looks like there are instances where sys.stdout/stderr contain file handles that are invalid. We should be tolerant of this for hook I/O redirection, as our primary concern is not garbling our own output stream.

hooks: delay I/O redirection until we actually run a hook (issue3711) We were attempting to redirect I/O even if no hook was actually getting called. This defers redirection until we've found something to do.

util: make chunkbuffer non-quadratic on Windows The old str-based += collector performed very nicely on Linux, but turns out to be quadratically expensive on Windows, causing chunkbuffer to dominate in profiles. This list-based version has been measured to significantly improve performance with large chunks on Windows, with negligible overall overhead on Linux (though microbenchmarks show it to be about 50% slower). This may increase memory overhead where += didn't behave quadratically. If we want to gather up 1G of data to join, we temporarily have 1G in our list and 1G in our string.