spanset: directly use __contains__ instead of a lambda Spanset are massively used in revset. First because the initial subset itself is a repo wide spanset. We speed up the __and__ operation by getting rid of a gratuitous lambda call. A more long terms solution would be to: 1. speed up operation between spansets, 2. have a special smartset for `all` revisions. In the mean time, this is a very simple fix that buyback some of the performance regression. Below is performance benchmark for trival `and` operation between two spansets. (Run on an unspecified fairly large repository.) revset tip:0 2.9.2) wall 0.282543 comb 0.280000 user 0.260000 sys 0.020000 (best of 35) before) wall 0.819181 comb 0.820000 user 0.820000 sys 0.000000 (best of 12) after) wall 0.645358 comb 0.650000 user 0.650000 sys 0.000000 (best of 16) Proof of concept implementation of an `all` smartset brings this to 0.10 but it's too invasive for stable.

transaction: fix file descriptor leak for journal.backupfiles The journal.backupfiles descriptor wasn't being closed. This resulted in hgsubversion test runs having a bagillion descriptors open, which crashed on platforms with low open file limits (like OSX).

revset: also inline spanset._contained in __len__ For consistency with what happen in `__contains__`, we inline the range test into `__len__` too.

revset: inline spanset containment check (fix perf regression) Calling a function is super expensive in python. We inline the trivial range comparison to get back to more sensible performance on common revset operation. Benchmark result below: Revision mapping: 0) 3f83fc5cfe71 2.9.2 release 1) bcfd44abad93 current @ 2) This revision revset #0: public() 0) wall 0.010890 comb 0.010000 user 0.010000 sys 0.000000 (best of 201) 1) wall 0.012109 comb 0.010000 user 0.010000 sys 0.000000 (best of 199) 2) wall 0.012211 comb 0.020000 user 0.020000 sys 0.000000 (best of 197) revset #1: :10000 and public() 0) wall 0.007141 comb 0.010000 user 0.010000 sys 0.000000 (best of 361) 1) wall 0.014139 comb 0.010000 user 0.010000 sys 0.000000 (best of 186) 2) wall 0.008334 comb 0.010000 user 0.010000 sys 0.000000 (best of 308) revset #2: draft() 0) wall 0.009610 comb 0.010000 user 0.010000 sys 0.000000 (best of 279) 1) wall 0.010942 comb 0.010000 user 0.010000 sys 0.000000 (best of 243) 2) wall 0.011036 comb 0.010000 user 0.010000 sys 0.000000 (best of 239) revset #3: :10000 and draft() 0) wall 0.006852 comb 0.010000 user 0.010000 sys 0.000000 (best of 383) 1) wall 0.014641 comb 0.010000 user 0.010000 sys 0.000000 (best of 183) 2) wall 0.008314 comb 0.010000 user 0.010000 sys 0.000000 (best of 299) We can see this changeset gains back the regression for `and` operation on spanset. We are still a bit slowerfor the `public()` and `draft()`. Predicates not touched by this changeset.

ancestor: silence multiple ancestor warning outside of merge (issue4234) The current situation is a bit of a layering violation as merge-specific knowledge is pushed down to lower layers and leaks merge assumptions into other code paths. Here, we simply silence the warning with a hack. Both the warning and the hack will probably go away in the near future when bid merge is made the default.

revsetbenchmark: fix error raising We want to display the commands, not all arguments of the function. (The old code actually crash, failing to joining a list of lists.)

revset: fix revision filtering in spanset.contains (regression) The argument is `x` but the variable tested for filtering is `rev`. `rev` happens to be a revset methods, ... never part of the filtered revs. This method is now using `rev` for everything.

graft: do not use `.remove` on a smart set (regression) Revset calls use to return a list. Graft use to mutate that list. We cannot do this anymore leading to a crash when grafting multiple changeset with a revset. File ".../mercurial/commands.py", line 3117, in graft revs.remove(rev) AttributeError: '_addset' object has no attribute 'remove' We are late in code-freeze so we make the shortest possible fix by turning it back to a list.

help: clarify distinction among `contains`/`file`/`filelog` For a Mercurial new-comer, the distinction between `contains(x)`, `file(x)`, and `filelog(x)` in the "revsets" help page may not be obvious. This commit tries to make things more obvious (text based on an explanation from Matt in an FB group thread).

discovery: don't report all "unsynced" remote heads (issue4230) 8a9e0b523d2d made discovery more helpful - too helpful for some extreme use cases. Instead, we arbitrarily limit the list it at 4 and add 'or more'.