revlog: add an aggressivemergedelta option This adds an option for delta'ing against both p1 and p2 when applying merge revisions and picking whichever is smallest. Some before and after stats on manifest.d size: internal large repo: before: 1.2 GB after: 930 MB mozilla-central: before: 261 MB after: 92 MB

revlog: change generaldelta delta parent heuristic The old generaldelta heuristic was "if p1 (or p2) was closer than the last full text, use it, otherwise use prev". This was problematic when a repo contained multiple branches that were very different. If commits to branch A were pushed, and the last full text was branch B, it would generate a fulltext. Then if branch B was pushed, it would generate another fulltext. The problem is that the last fulltext (and delta'ing against `prev` in general) has no correlation with the contents of the incoming revision, and therefore will always have degenerate cases. According to the blame, that algorithm was chosen to minimize the chain length. Since there is already code that protects against that (the delta-vs-fulltext code), and since it has been improved since the original generaldelta algorithm went in (2011), I believe the chain length criteria will still be preserved. The new algorithm always diffs against p1 (or p2 if it's closer), unless the resulting delta will fail the delta-vs-fulltext check, in which case we delta against prev. Some before and after stats on manifest.d size. internal large repo old heuristic - 2.0 GB new heuristic - 1.2 GB mozilla-central old heuristic - 242 MB new heuristic - 261 MB The regression in mozilla central is due to the new heuristic choosing p2r as the delta when it's closer to the tip. Switching the algorithm to always prefer p1r brings the size back down (242 MB). This is result of the way in which mozilla does merges and pushes, and the result could easily swing the other direction in other repos (depending on if they merge X into Y or Y into X), but will never be as degenerate as before. I future patch will address the regression by introducing an optional, even more aggressive delta heuristic which will knock the mozilla manifest size down dramatically.

revlog: move textlen calculation to be above delta chooser This moves the textlen calculation to be above the delta chooser. Since textlen is needed for calling isgooddelta, we need it above the delta chooser so future patches can call isgooddelta.

revlog: move delta check to it's own function This moves the delta vs fulltext comparison to its own function. This will allow us to reuse the function in future patches for more efficient delta choices. As a side effect, this will also allow extensions to modify our delta criteria.

monoblue: add archive links on summary page

help: distinguish sections when multiple match (issue4802)

merge with stable

hghave: add a check for docker support This currently refuses to operate if on a non-Linux host. I suspect that Docker running on FreeBSD 11 or on an Illumos derivative would work fine, but I don't have ready access to such a system. On OS X using boot2docker (I used a hacky xhyve-based one for testing), it won't work because $TESTTEMP doesn't end up inside the set of directories that get forwarded to the boot2docker VM, so you can't actually drop debs in the $TESTTEMP at all. It would be possible (probably even trivial) to hack around this by using a randomly-named temporary directory inside the working directory, but that seems unlikely to be useful enough to justify the ugliness.

hghave: add a check for debian packaging tools

run-tests: add support for marking tests as very slow I want to add tests for our packaging rules, but those necessarily run a whole build, or possibly two if both native packaging and docker are available. This lets us flag such tests with a `#require slow` so that they don't unnecessarily slow down normal test runs.