tests/test-help-hide.t

copies-rust: use imrs::OrdSet instead of imrs::HashSet

This yield small speedup all over the board, and a large one for our slower
cases:

Repo            Case                                  Source-Rev   Dest-Rev      # of revisions  old time    new time      Difference    Factor    time per rev
---------------------------------------------------------------------------------------------------------------------------------------------------------------
mozilla-try     x0000_revs_xx000_added_x000_copies    89294cd501d9 7ccb2fc7ccb5 :  97052 revs,   2.034596 s,   1.465264 s,  -0.569332 s, × 0.7202,    15 µs/rev
mozilla-try     x0000_revs_x0000_added_x0000_copies   e928c65095ed e951f4ad123a :  52031 revs,   0.694030 s,   0.690376 s,  -0.003654 s, × 0.9947,    13 µs/rev
mozilla-try     x00000_revs_x_added_0_copies          6a320851d377 1ebb79acd503 : 363753 revs,   4.407723 s,   4.011322 s,  -0.396401 s, × 0.9101,    11 µs/rev
mozilla-try     x00000_revs_x00000_added_0_copies     dc8a3ca7010e d16fde900c9c :  34414 revs,   0.574355 s,   0.573541 s,  -0.000814 s, × 0.9986,    16 µs/rev
mozilla-try     x00000_revs_x_added_x_copies          5173c4b6f97c 95d83ee7242d : 362229 revs,   4.457827 s,   3.981133 s,  -0.476694 s, × 0.8931,    10 µs/rev
mozilla-try     x00000_revs_x000_added_x_copies       9126823d0e9c ca82787bb23c : 359344 revs,   4.351696 s,   3.996647 s,  -0.355049 s, × 0.9184,    11 µs/rev
mozilla-try     x00000_revs_x00000_added_x0000_copies 1b661134e2ca 1ae03d022d6d : 228985 revs,  80.828689 s,  50.244975 s, -30.583714 s, × 0.6216,   219 µs/rev
mozilla-try     x00000_revs_x00000_added_x000_copies  9b2a99adc05e 8e29777b48e6 : 382065 revs,  34.094064 s,  20.030023 s, -14.064041 s, × 0.5875,    52 µs/rev
private                                                                         : 459513 revs,  27.435529 s,  24.490825 s,  -2.944704 s, × 0.8927,    53 µs/rev

We also got significantly faster than the implementation using is_ancestors
except for one of our reference case:

Repo            Case                                  Source-Rev   Dest-Rev      # of revisions  old time    new time      Difference    Factor    time per rev
---------------------------------------------------------------------------------------------------------------------------------------------------------------
mozilla-try     x00000_revs_x_added_0_copies          6a320851d377 1ebb79acd503 : 363753 revs,   5.138169 s,   4.011322 s,  -1.126847 s, × 0.7807,    11 µs/rev
mozilla-try     x00000_revs_x_added_x_copies          5173c4b6f97c 95d83ee7242d : 362229 revs,   5.127809 s,   3.981133 s,  -1.146676 s, × 0.7764,    10 µs/rev
mozilla-try     x00000_revs_x000_added_x_copies       9126823d0e9c ca82787bb23c : 359344 revs,   4.971136 s,   3.996647 s,  -0.974489 s, × 0.8040,    11 µs/rev
mozilla-try     x00000_revs_x0000_added_x0000_copies  8d3fafa80d4b eb884023b810 : 192665 revs,   1.741678 s,   1.520607 s,  -0.221071 s, × 0.8731,     7 µs/rev
private                                                                         : 459513 revs,  37.179470 s,  24.490825 s, -12.688645 s, × 0.6587,    53 µs/rev
mozilla-try     x00000_revs_x00000_added_x0000_copies 1b661134e2ca 1ae03d022d6d : 228985 revs,  40.314822 s,  50.244975 s,  +9.930153 s, × 1.2463,   219 µs/rev


Below are three different benchmark comparing this changeset to:
* the previous one,
* the implementation based on `is_anscestors`,
* the filelog copy tracing.


### Compared to the previous ones

Repo            Case                                  Source-Rev   Dest-Rev      # of revisions  old time    new time      Difference    Factor    time per rev
---------------------------------------------------------------------------------------------------------------------------------------------------------------
mercurial       x_revs_x_added_0_copies               ad6b123de1c7 39cfcef4f463 :      1 revs,   0.000043 s,   0.000041 s,  -0.000002 s, × 0.9535,    41 µs/rev
mercurial       x_revs_x_added_x_copies               2b1c78674230 0c1d10351869 :      6 revs,   0.000114 s,   0.000116 s,  +0.000002 s, × 1.0175,    19 µs/rev
mercurial       x000_revs_x000_added_x_copies         81f8ff2a9bf2 dd3267698d84 :   1032 revs,   0.004899 s,   0.004933 s,  +0.000034 s, × 1.0069,     4 µs/rev
pypy            x_revs_x_added_0_copies               aed021ee8ae8 099ed31b181b :      9 revs,   0.000196 s,   0.000193 s,  -0.000003 s, × 0.9847,    21 µs/rev
pypy            x_revs_x000_added_0_copies            4aa4e1f8e19a 359343b9ac0e :      1 revs,   0.000049 s,   0.000048 s,  -0.000001 s, × 0.9796,    48 µs/rev
pypy            x_revs_x_added_x_copies               ac52eb7bbbb0 72e022663155 :      7 revs,   0.000117 s,   0.000114 s,  -0.000003 s, × 0.9744,    16 µs/rev
pypy            x_revs_x00_added_x_copies             c3b14617fbd7 ace7255d9a26 :      1 revs,   0.6f1f4a s,   0.000319 s,  -0.000003 s, × 0.9907,   319 µs/rev
pypy            x_revs_x000_added_x000_copies         df6f7a526b60 a83dc6a2d56f :      6 revs,   0.011856 s,   0.012025 s,  +0.000169 s, × 1.0143,  2004 µs/rev
pypy            x000_revs_xx00_added_0_copies         89a76aede314 2f22446ff07e :   4785 revs,   0.050992 s,   0.050525 s,  -0.000467 s, × 0.9908,    10 µs/rev
pypy            x000_revs_x000_added_x_copies         8a3b5bfd266e 2c68e87c3efe :   6780 revs,   0.087444 s,   0.085713 s,  -0.001731 s, × 0.9802,    12 µs/rev
pypy            x000_revs_x000_added_x000_copies      89a76aede314 7b3dda341c84 :   5441 revs,   0.062487 s,   0.061825 s,  -0.000662 s, × 0.9894,    11 µs/rev
pypy            x0000_revs_x_added_0_copies           d1defd0dc478 c9cb1334cc78 :  43645 revs,   0.634909 s,   0.543998 s,  -0.090911 s, × 0.8568,    12 µs/rev
pypy            x0000_revs_xx000_added_0_copies       bf2c629d0071 4ffed77c095c :      2 revs,   0.013360 s,   0.013455 s,  +0.000095 s, × 1.0071,  6727 µs/rev
pypy            x0000_revs_xx000_added_x000_copies    08ea3258278e d9fa043f30c0 :  11316 revs,   0.120775 s,   0.117479 s,  -0.003296 s, × 0.9727,    10 µs/rev
netbeans        x_revs_x_added_0_copies               fb0955ffcbcd a01e9239f9e7 :      2 revs,   0.000085 s,   0.000084 s,  -0.000001 s, × 0.9882,    42 µs/rev
netbeans        x_revs_x000_added_0_copies            6f360122949f 20eb231cc7d0 :      2 revs,   0.000108 s,   0.000111 s,  +0.000003 s, × 1.0278,    55 µs/rev
netbeans        x_revs_x_added_x_copies               1ada3faf6fb6 5a39d12eecf4 :      3 revs,   0.000176 s,   0.000175 s,  -0.000001 s, × 0.9943,    58 µs/rev
netbeans        x_revs_x00_added_x_copies             35be93ba1e2c 9eec5e90c05f :      9 revs,   0.000747 s,   0.000732 s,  -0.000015 s, × 0.9799,    81 µs/rev
netbeans        x000_revs_xx00_added_0_copies         eac3045b4fdd 51d4ae7f1290 :   1421 revs,   0.010128 s,   0.010062 s,  -0.000066 s, × 0.9935,     7 µs/rev
netbeans        x000_revs_x000_added_x_copies         e2063d266acd 6081d72689dc :   1533 revs,   0.015899 s,   0.015659 s,  -0.000240 s, × 0.9849,    10 µs/rev
netbeans        x000_revs_x000_added_x000_copies      ff453e9fee32 411350406ec2 :   5750 revs,   0.062215 s,   0.062744 s,  +0.000529 s, × 1.0085,    10 µs/rev
netbeans        x0000_revs_xx000_added_x000_copies    588c2d1ced70 1aad62e59ddd :  66949 revs,   0.521004 s,   0.499449 s,  -0.021555 s, × 0.9586,     7 µs/rev
mozilla-central x_revs_x_added_0_copies               3697f962bb7b 7015fcdd43a2 :      2 revs,   0.000090 s,   0.000088 s,  -0.000002 s, × 0.9778,    44 µs/rev
mozilla-central x_revs_x000_added_0_copies            dd390860c6c9 40d0c5bed75d :      8 revs,   0.000264 s,   0.000266 s,  +0.000002 s, × 1.0076,    33 µs/rev
mozilla-central x_revs_x_added_x_copies               8d198483ae3b 14207ffc2b2f :      9 revs,   0.000186 s,   0.000182 s,  -0.000004 s, × 0.9785,    20 µs/rev
mozilla-central x_revs_x00_added_x_copies             98cbc58cc6bc 446a150332c3 :      7 revs,   0.000660 s,   0.000656 s,  -0.000004 s, × 0.9939,    93 µs/rev
mozilla-central x_revs_x000_added_x000_copies         3c684b4b8f68 0a5e72d1b479 :      3 revs,   0.003542 s,   0.003389 s,  -0.000153 s, × 0.9568,  1129 µs/rev
mozilla-central x_revs_x0000_added_x0000_copies       effb563bb7e5 c07a39dc4e80 :      6 revs,   0.071574 s,   0.075882 s,  +0.004308 s, × 1.0602, 12647 µs/rev
mozilla-central x000_revs_xx00_added_0_copies         6100d773079a 04a55431795e :   1593 revs,   0.006498 s,   0.006479 s,  -0.000019 s, × 0.9971,     4 µs/rev
mozilla-central x000_revs_x000_added_x_copies         9f17a6fc04f9 2d37b966abed :     41 revs,   0.005206 s,   0.004889 s,  -0.000317 s, × 0.9391,   119 µs/rev
mozilla-central x000_revs_x000_added_x000_copies      7c97034feb78 4407bd0c6330 :   7839 revs,   0.065535 s,   0.064394 s,  -0.001141 s, × 0.9826,     8 µs/rev
mozilla-central x0000_revs_xx000_added_0_copies       9eec5917337d 67118cc6dcad :    615 revs,   0.027139 s,   0.026815 s,  -0.000324 s, × 0.9881,    43 µs/rev
mozilla-central x0000_revs_xx000_added_x000_copies    f78c615a656c 96a38b690156 :  30263 revs,   0.201924 s,   0.cc85eb s,  +0.000940 s, × 1.0047,     6 µs/rev
mozilla-central x00000_revs_x0000_added_x0000_copies  6832ae71433c 4c222a1d9a00 : 153721 revs,   1.257201 s,   1.219445 s,  -0.037756 s, × 0.9700,     7 µs/rev
mozilla-central x00000_revs_x00000_added_x000_copies  76caed42cf7c 1daa622bbe42 : 204976 revs,   1.663045 s,   1.613857 s,  -0.049188 s, × 0.9704,     7 µs/rev
mozilla-try     x_revs_x_added_0_copies               aaf6dde0deb8 9790f499805a :      2 revs,   0.000866 s,   0.000873 s,  +0.000007 s, × 1.0081,   436 µs/rev
mozilla-try     x_revs_x000_added_0_copies            d8d0222927b4 5bb8ce8c7450 :      2 revs,   0.000883 s,   0.000885 s,  +0.000002 s, × 1.0023,   442 µs/rev
mozilla-try     x_revs_x_added_x_copies               092fcca11bdb 936255a0384a :      4 revs,   0.000163 s,   0.000161 s,  -0.000002 s, × 0.9877,    40 µs/rev
mozilla-try     x_revs_x00_added_x_copies             b53d2fadbdb5 017afae788ec :      2 revs,   0.001139 s,   0.001138 s,  -0.000001 s, × 0.9991,   569 µs/rev
mozilla-try     x_revs_x000_added_x000_copies         20408ad61ce5 6f0ee96e21ad :      1 revs,   0.032753 s,   0.033399 s,  +0.000646 s, × 1.0197, 33399 µs/rev
mozilla-try     x_revs_x0000_added_x0000_copies       effb563bb7e5 c07a39dc4e80 :      6 revs,   0.073266 s,   0.075445 s,  +0.002179 s, × 1.0297, 12574 µs/rev
mozilla-try     x000_revs_xx00_added_0_copies         6100d773079a 04a55431795e :   1593 revs,   0.006567 s,   0.006456 s,  -0.000111 s, × 0.9831,     4 µs/rev
mozilla-try     x000_revs_x000_added_x_copies         9f17a6fc04f9 2d37b966abed :     41 revs,   0.005427 s,   0.005462 s,  +0.000035 s, × 1.0064,   133 µs/rev
mozilla-try     x000_revs_x000_added_x000_copies      1346fd0130e4 4c65cbdabc1f :   6657 revs,   0.064058 s,   0.064117 s,  +0.000059 s, × 1.0009,     9 µs/rev
mozilla-try     x0000_revs_x_added_0_copies           63519bfd42ee a36a2a865d92 :  40314 revs,   0.303320 s,   0.297563 s,  -0.005757 s, × 0.9810,     7 µs/rev
mozilla-try     x0000_revs_x_added_x_copies           9fe69ff0762d bcabf2a78927 :  38690 revs,   0.288456 s,   0.282463 s,  -0.005993 s, × 0.9792,     7 µs/rev
mozilla-try     x0000_revs_xx000_added_x_copies       156f6e2674f2 4d0f2c178e66 :   8598 revs,   0.085925 s,   0.084038 s,  -0.001887 s, × 0.9780,     9 µs/rev
mozilla-try     x0000_revs_xx000_added_0_copies       9eec5917337d 67118cc6dcad :    615 revs,   0.027302 s,   0.027306 s,  +0.000004 s, × 1.0001,    44 µs/rev
mozilla-try     x0000_revs_xx000_added_x000_copies    89294cd501d9 7ccb2fc7ccb5 :  97052 revs,   2.034596 s,   1.465264 s,  -0.569332 s, × 0.7202,    15 µs/rev
mozilla-try     x0000_revs_x0000_added_x0000_copies   e928c65095ed e951f4ad123a :  52031 revs,   0.694030 s,   0.690376 s,  -0.003654 s, × 0.9947,    13 µs/rev
mozilla-try     x00000_revs_x_added_0_copies          6a320851d377 1ebb79acd503 : 363753 revs,   4.407723 s,   4.011322 s,  -0.396401 s, × 0.9101,    11 µs/rev
mozilla-try     x00000_revs_x00000_added_0_copies     dc8a3ca7010e d16fde900c9c :  34414 revs,   0.574355 s,   0.573541 s,  -0.000814 s, × 0.9986,    16 µs/rev
mozilla-try     x00000_revs_x_added_x_copies          5173c4b6f97c 95d83ee7242d : 362229 revs,   4.457827 s,   3.981133 s,  -0.476694 s, × 0.8931,    10 µs/rev
mozilla-try     x00000_revs_x000_added_x_copies       9126823d0e9c ca82787bb23c : 359344 revs,   4.351696 s,   3.996647 s,  -0.355049 s, × 0.9184,    11 µs/rev
mozilla-try     x00000_revs_x0000_added_x0000_copies  8d3fafa80d4b eb884023b810 : 192665 revs,   1.570065 s,   1.520607 s,  -0.049458 s, × 0.9685,     7 µs/rev
mozilla-try     x00000_revs_x00000_added_x0000_copies 1b661134e2ca 1ae03d022d6d : 228985 revs,  80.828689 s,  50.244975 s, -30.583714 s, × 0.6216,   219 µs/rev
mozilla-try     x00000_revs_x00000_added_x000_copies  9b2a99adc05e 8e29777b48e6 : 382065 revs,  34.094064 s,  20.030023 s, -14.064041 s, × 0.5875,    52 µs/rev
private                                                                         : 459513 revs,  27.435529 s,  24.490825 s,  -2.944704 s, × 0.8927,    53 µs/rev

### Compared to the implementation using `is_anscestor`

Repo            Case                                  Source-Rev   Dest-Rev      # of revisions  old time    new time      Difference    Factor    time per rev
---------------------------------------------------------------------------------------------------------------------------------------------------------------
mercurial       x_revs_x_added_0_copies               ad6b123de1c7 39cfcef4f463 :      1 revs,   0.000042 s,   0.000041 s,  -0.000001 s, × 0.9762,    41 µs/rev
mercurial       x_revs_x_added_x_copies               2b1c78674230 0c1d10351869 :      6 revs,   0.000110 s,   0.000116 s,  +0.000006 s, × 1.0545,    19 µs/rev
mercurial       x000_revs_x000_added_x_copies         81f8ff2a9bf2 dd3267698d84 :   1032 revs,   0.004945 s,   0.004933 s,  -0.000012 s, × 0.9976,     4 µs/rev
pypy            x_revs_x_added_0_copies               aed021ee8ae8 099ed31b181b :      9 revs,   0.000192 s,   0.000193 s,  +0.000001 s, × 1.0052,    21 µs/rev
pypy            x_revs_x000_added_0_copies            4aa4e1f8e19a 359343b9ac0e :      1 revs,   0.000049 s,   0.000048 s,  -0.000001 s, × 0.9796,    48 µs/rev
pypy            x_revs_x_added_x_copies               ac52eb7bbbb0 72e022663155 :      7 revs,   0.000112 s,   0.000114 s,  +0.000002 s, × 1.0179,    16 µs/rev
pypy            x_revs_x00_added_x_copies             c3b14617fbd7 ace7255d9a26 :      1 revs,   0.000323 s,   0.000319 s,  -0.000004 s, × 0.9876,   319 µs/rev
pypy            x_revs_x000_added_x000_copies         df6f7a526b60 a83dc6a2d56f :      6 revs,   0.010042 s,   0.012025 s,  +0.001983 s, × 1.1975,  2004 µs/rev
pypy            x000_revs_xx00_added_0_copies         89a76aede314 2f22446ff07e :   4785 revs,   0.049813 s,   0.050525 s,  +0.000712 s, × 1.0143,    10 µs/rev
pypy            x000_revs_x000_added_x_copies         8a3b5bfd266e 2c68e87c3efe :   6780 revs,   0.079937 s,   0.085713 s,  +0.005776 s, × 1.0723,    12 µs/rev
pypy            x000_revs_x000_added_x000_copies      89a76aede314 7b3dda341c84 :   5441 revs,   0.059412 s,   0.061825 s,  +0.002413 s, × 1.0406,    11 µs/rev
pypy            x0000_revs_x_added_0_copies           d1defd0dc478 c9cb1334cc78 :  43645 revs,   0.533769 s,   0.543998 s,  +0.010229 s, × 1.0192,    12 µs/rev
pypy            x0000_revs_xx000_added_0_copies       bf2c629d0071 4ffed77c095c :      2 revs,   0.013147 s,   0.013455 s,  +0.000308 s, × 1.0234,  6727 µs/rev
pypy            x0000_revs_xx000_added_x000_copies    08ea3258278e d9fa043f30c0 :  11316 revs,   0.110680 s,   0.117479 s,  +0.006799 s, × 1.0614,    10 µs/rev
netbeans        x_revs_x_added_0_copies               fb0955ffcbcd a01e9239f9e7 :      2 revs,   0.000085 s,   0.000084 s,  -0.000001 s, × 0.9882,    42 µs/rev
netbeans        x_revs_x000_added_0_copies            6f360122949f 20eb231cc7d0 :      2 revs,   0.000107 s,   0.000111 s,  +0.000004 s, × 1.0374,    55 µs/rev
netbeans        x_revs_x_added_x_copies               1ada3faf6fb6 5a39d12eecf4 :      3 revs,   0.000175 s,   0.000175 s,  +0.000000 s, × 1.0000,    58 µs/rev
netbeans        x_revs_x00_added_x_copies             35be93ba1e2c 9eec5e90c05f :      9 revs,   0.000720 s,   0.000732 s,  +0.000012 s, × 1.0167,    81 µs/rev
netbeans        x000_revs_xx00_added_0_copies         eac3045b4fdd 51d4ae7f1290 :   1421 revs,   0.010019 s,   0.010062 s,  +0.000043 s, × 1.0043,     7 µs/rev
netbeans        x000_revs_x000_added_x_copies         e2063d266acd 6081d72689dc :   1533 revs,   0.015602 s,   0.015659 s,  +0.000057 s, × 1.0037,    10 µs/rev
netbeans        x000_revs_x000_added_x000_copies      ff453e9fee32 411350406ec2 :   5750 revs,   0.058759 s,   0.062744 s,  +0.003985 s, × 1.0678,    10 µs/rev
netbeans        x0000_revs_xx000_added_x000_copies    588c2d1ced70 1aad62e59ddd :  66949 revs,   0.491550 s,   0.499449 s,  +0.007899 s, × 1.0161,     7 µs/rev
mozilla-central x_revs_x_added_0_copies               3697f962bb7b 7015fcdd43a2 :      2 revs,   0.000087 s,   0.000088 s,  +0.000001 s, × 1.0115,    44 µs/rev
mozilla-central x_revs_x000_added_0_copies            dd390860c6c9 40d0c5bed75d :      8 revs,   0.000268 s,   0.000266 s,  -0.000002 s, × 0.9925,    33 µs/rev
mozilla-central x_revs_x_added_x_copies               8d198483ae3b 14207ffc2b2f :      9 revs,   0.000181 s,   0.000182 s,  +0.000001 s, × 1.0055,    20 µs/rev
mozilla-central x_revs_x00_added_x_copies             98cbc58cc6bc 446a150332c3 :      7 revs,   0.000661 s,   0.000656 s,  -0.000005 s, × 0.9924,    93 µs/rev
mozilla-central x_revs_x000_added_x000_copies         3c684b4b8f68 0a5e72d1b479 :      3 revs,   0.003256 s,   0.003389 s,  +0.000133 s, × 1.0408,  1129 µs/rev
mozilla-central x_revs_x0000_added_x0000_copies       effb563bb7e5 c07a39dc4e80 :      6 revs,   0.066749 s,   0.075882 s,  +0.009133 s, × 1.1368, 12647 µs/rev
mozilla-central x000_revs_xx00_added_0_copies         6100d773079a 04a55431795e :   1593 revs,   0.006462 s,   0.006479 s,  +0.000017 s, × 1.0026,     4 µs/rev
mozilla-central x000_revs_x000_added_x_copies         9f17a6fc04f9 2d37b966abed :     41 revs,   0.004919 s,   0.004889 s,  -0.000030 s, × 0.9939,   119 µs/rev
mozilla-central x000_revs_x000_added_x000_copies      7c97034feb78 4407bd0c6330 :   7839 revs,   0.062421 s,   0.064394 s,  +0.001973 s, × 1.0316,     8 µs/rev
mozilla-central x0000_revs_xx000_added_0_copies       9eec5917337d 67118cc6dcad :    615 revs,   0.026633 s,   0.026815 s,  +0.000182 s, × 1.0068,    43 µs/rev
mozilla-central x0000_revs_xx000_added_x000_copies    f78c615a656c 96a38b690156 :  30263 revs,   0.197792 s,   0.cc85eb s,  +0.005072 s, × 1.0256,     6 µs/rev
mozilla-central x00000_revs_x0000_added_x0000_copies  6832ae71433c 4c222a1d9a00 : 153721 revs,   1.259970 s,   1.219445 s,  -0.040525 s, × 0.9678,     7 µs/rev
mozilla-central x00000_revs_x00000_added_x000_copies  76caed42cf7c 1daa622bbe42 : 204976 revs,   1.689184 s,   1.613857 s,  -0.075327 s, × 0.9554,     7 µs/rev
mozilla-try     x_revs_x_added_0_copies               aaf6dde0deb8 9790f499805a :      2 revs,   0.000865 s,   0.000873 s,  +0.000008 s, × 1.0092,   436 µs/rev
mozilla-try     x_revs_x000_added_0_copies            d8d0222927b4 5bb8ce8c7450 :      2 revs,   0.000893 s,   0.000885 s,  -0.000008 s, × 0.9910,   442 µs/rev
mozilla-try     x_revs_x_added_x_copies               092fcca11bdb 936255a0384a :      4 revs,   0.000172 s,   0.000161 s,  -0.000011 s, × 0.9360,    40 µs/rev
mozilla-try     x_revs_x00_added_x_copies             b53d2fadbdb5 017afae788ec :      2 revs,   0.001159 s,   0.001138 s,  -0.000021 s, × 0.9819,   569 µs/rev
mozilla-try     x_revs_x000_added_x000_copies         20408ad61ce5 6f0ee96e21ad :      1 revs,   0.031621 s,   0.033399 s,  +0.001778 s, × 1.0562, 33399 µs/rev
mozilla-try     x_revs_x0000_added_x0000_copies       effb563bb7e5 c07a39dc4e80 :      6 revs,   0.068571 s,   0.075445 s,  +0.006874 s, × 1.1002, 12574 µs/rev
mozilla-try     x000_revs_xx00_added_0_copies         6100d773079a 04a55431795e :   1593 revs,   0.006452 s,   0.006456 s,  +0.000004 s, × 1.0006,     4 µs/rev
mozilla-try     x000_revs_x000_added_x_copies         9f17a6fc04f9 2d37b966abed :     41 revs,   0.005443 s,   0.005462 s,  +0.000019 s, × 1.0035,   133 µs/rev
mozilla-try     x000_revs_x000_added_x000_copies      1346fd0130e4 4c65cbdabc1f :   6657 revs,   0.063180 s,   0.064117 s,  +0.000937 s, × 1.0148,     9 µs/rev
mozilla-try     x0000_revs_x_added_0_copies           63519bfd42ee a36a2a865d92 :  40314 revs,   0.293564 s,   0.297563 s,  +0.003999 s, × 1.0136,     7 µs/rev
mozilla-try     x0000_revs_x_added_x_copies           9fe69ff0762d bcabf2a78927 :  38690 revs,   0.286595 s,   0.282463 s,  -0.004132 s, × 0.9856,     7 µs/rev
mozilla-try     x0000_revs_xx000_added_x_copies       156f6e2674f2 4d0f2c178e66 :   8598 revs,   0.083256 s,   0.084038 s,  +0.000782 s, × 1.0094,     9 µs/rev
mozilla-try     x0000_revs_xx000_added_0_copies       9eec5917337d 67118cc6dcad :    615 revs,   0.027282 s,   0.027306 s,  +0.000024 s, × 1.0009,    44 µs/rev
mozilla-try     x0000_revs_xx000_added_x000_copies    89294cd501d9 7ccb2fc7ccb5 :  97052 revs,   1.343373 s,   1.465264 s,  +0.121891 s, × 1.0907,    15 µs/rev
mozilla-try     x0000_revs_x0000_added_x0000_copies   e928c65095ed e951f4ad123a :  52031 revs,   0.665737 s,   0.690376 s,  +0.024639 s, × 1.0370,    13 µs/rev
mozilla-try     x00000_revs_x_added_0_copies          6a320851d377 1ebb79acd503 : 363753 revs,   5.138169 s,   4.011322 s,  -1.126847 s, × 0.7807,    11 µs/rev
mozilla-try     x00000_revs_x00000_added_0_copies     dc8a3ca7010e d16fde900c9c :  34414 revs,   0.573276 s,   0.573541 s,  +0.000265 s, × 1.0005,    16 µs/rev
mozilla-try     x00000_revs_x_added_x_copies          5173c4b6f97c 95d83ee7242d : 362229 revs,   5.127809 s,   3.981133 s,  -1.146676 s, × 0.7764,    10 µs/rev
mozilla-try     x00000_revs_x000_added_x_copies       9126823d0e9c ca82787bb23c : 359344 revs,   4.971136 s,   3.996647 s,  -0.974489 s, × 0.8040,    11 µs/rev
mozilla-try     x00000_revs_x0000_added_x0000_copies  8d3fafa80d4b eb884023b810 : 192665 revs,   1.741678 s,   1.520607 s,  -0.221071 s, × 0.8731,     7 µs/rev
mozilla-try     x00000_revs_x00000_added_x0000_copies 1b661134e2ca 1ae03d022d6d : 228985 revs,  40.314822 s,  50.244975 s,  +9.930153 s, × 1.2463,   219 µs/rev
mozilla-try     x00000_revs_x00000_added_x000_copies  9b2a99adc05e 8e29777b48e6 : 382065 revs,  20.048029 s,  20.030023 s,  -0.018006 s, × 0.9991,    52 µs/rev
private                                                                         : 459513 revs,  37.179470 s,  24.490825 s, -12.688645 s, × 0.6587,    53 µs/rev

### Compared to the filelog based copy tracing

Repo            Case                                  Source-Rev   Dest-Rev      # of revisions  old time    new time      Difference    Factor    time per rev
---------------------------------------------------------------------------------------------------------------------------------------------------------------
mercurial       x_revs_x_added_0_copies               ad6b123de1c7 39cfcef4f463 :      1 revs,  0.000918 s,  0.000041 s,  -0.000877 s, × 0.044662,    40 µs/rev
mercurial       x_revs_x_added_x_copies               2b1c78674230 0c1d10351869 :      6 revs,  0.001853 s,  0.000116 s,  -0.001737 s, × 0.062601,    19 µs/rev
mercurial       x000_revs_x000_added_x_copies         81f8ff2a9bf2 dd3267698d84 :   1032 revs,  0.018994 s,  0.004933 s,  -0.014061 s, × 0.259714,     4 µs/rev
pypy            x_revs_x_added_0_copies               aed021ee8ae8 099ed31b181b :      9 revs,  0.001532 s,  0.000193 s,  -0.001339 s, × 0.125979,    21 µs/rev
pypy            x_revs_x000_added_0_copies            4aa4e1f8e19a 359343b9ac0e :      1 revs,  0.210633 s,  0.000048 s,  -0.210585 s, × 0.000228,    47 µs/rev
pypy            x_revs_x_added_x_copies               ac52eb7bbbb0 72e022663155 :      7 revs,  0.017041 s,  0.000114 s,  -0.016927 s, × 0.006690,    16 µs/rev
pypy            x_revs_x00_added_x_copies             c3b14617fbd7 ace7255d9a26 :      1 revs,  0.019474 s,  0.000319 s,  -0.019155 s, × 0.016381,   318 µs/rev
pypy            x_revs_x000_added_x000_copies         df6f7a526b60 a83dc6a2d56f :      6 revs,  0.763136 s,  0.012025 s,  -0.751111 s, × 0.015757,  2003 µs/rev
pypy            x000_revs_xx00_added_0_copies         89a76aede314 2f22446ff07e :   4785 revs,  1.226569 s,  0.050525 s,  -1.176044 s, × 0.041192,    10 µs/rev
pypy            x000_revs_x000_added_x_copies         8a3b5bfd266e 2c68e87c3efe :   6780 revs,  1.314572 s,  0.085713 s,  -1.228859 s, × 0.065202,    12 µs/rev
pypy            x000_revs_x000_added_x000_copies      89a76aede314 7b3dda341c84 :   5441 revs,  1.686022 s,  0.061825 s,  -1.624197 s, × 0.036669,    11 µs/rev
pypy            x0000_revs_x_added_0_copies           d1defd0dc478 c9cb1334cc78 :  43645 revs,  0.001110 s,  0.543998 s,  +0.542888 s, × 490.0882,    12 µs/rev
pypy            x0000_revs_xx000_added_0_copies       bf2c629d0071 4ffed77c095c :      2 revs,  1.106265 s,  0.013455 s,  -1.092810 s, × 0.012163,  6724 µs/rev
pypy            x0000_revs_xx000_added_x000_copies    08ea3258278e d9fa043f30c0 :  11316 revs,  1.377398 s,  0.117479 s,  -1.259919 s, × 0.085291,    10 µs/rev
netbeans        x_revs_x_added_0_copies               fb0955ffcbcd a01e9239f9e7 :      2 revs,  0.028579 s,  0.000084 s,  -0.028495 s, × 0.002939,    41 µs/rev
netbeans        x_revs_x000_added_0_copies            6f360122949f 20eb231cc7d0 :      2 revs,  0.133644 s,  0.000111 s,  -0.133533 s, × 0.000831,    55 µs/rev
netbeans        x_revs_x_added_x_copies               1ada3faf6fb6 5a39d12eecf4 :      3 revs,  0.025988 s,  0.000175 s,  -0.025813 s, × 0.006734,    58 µs/rev
netbeans        x_revs_x00_added_x_copies             35be93ba1e2c 9eec5e90c05f :      9 revs,  0.053011 s,  0.000732 s,  -0.052279 s, × 0.013808,    81 µs/rev
netbeans        x000_revs_xx00_added_0_copies         eac3045b4fdd 51d4ae7f1290 :   1421 revs,  0.037858 s,  0.010062 s,  -0.027796 s, × 0.265783,     7 µs/rev
netbeans        x000_revs_x000_added_x_copies         e2063d266acd 6081d72689dc :   1533 revs,  0.200517 s,  0.015659 s,  -0.184858 s, × 0.078093,    10 µs/rev
netbeans        x000_revs_x000_added_x000_copies      ff453e9fee32 411350406ec2 :   5750 revs,  0.964542 s,  0.062744 s,  -0.901798 s, × 0.065051,    10 µs/rev
netbeans        x0000_revs_xx000_added_x000_copies    588c2d1ced70 1aad62e59ddd :  66949 revs,  3.976210 s,  0.499449 s,  -3.476761 s, × 0.125609,     7 µs/rev
mozilla-central x_revs_x_added_0_copies               3697f962bb7b 7015fcdd43a2 :      2 revs,  0.025172 s,  0.000088 s,  -0.025084 s, × 0.003496,    43 µs/rev
mozilla-central x_revs_x000_added_0_copies            dd390860c6c9 40d0c5bed75d :      8 revs,  0.145144 s,  0.000266 s,  -0.144878 s, × 0.001833,    33 µs/rev
mozilla-central x_revs_x_added_x_copies               8d198483ae3b 14207ffc2b2f :      9 revs,  0.026139 s,  0.000182 s,  -0.025957 s, × 0.006963,    20 µs/rev
mozilla-central x_revs_x00_added_x_copies             98cbc58cc6bc 446a150332c3 :      7 revs,  0.086184 s,  0.000656 s,  -0.085528 s, × 0.007612,    93 µs/rev
mozilla-central x_revs_x000_added_x000_copies         3c684b4b8f68 0a5e72d1b479 :      3 revs,  0.203187 s,  0.003389 s,  -0.199798 s, × 0.016679,  1129 µs/rev
mozilla-central x_revs_x0000_added_x0000_copies       effb563bb7e5 c07a39dc4e80 :      6 revs,  2.255675 s,  0.075882 s,  -2.179793 s, × 0.033640, 12644 µs/rev
mozilla-central x000_revs_xx00_added_0_copies         6100d773079a 04a55431795e :   1593 revs,  0.091147 s,  0.006479 s,  -0.084668 s, × 0.071083,     4 µs/rev
mozilla-central x000_revs_x000_added_x_copies         9f17a6fc04f9 2d37b966abed :     41 revs,  0.767530 s,  0.004889 s,  -0.762641 s, × 0.006370,   119 µs/rev
mozilla-central x000_revs_x000_added_x000_copies      7c97034feb78 4407bd0c6330 :   7839 revs,  1.185330 s,  0.064394 s,  -1.120936 s, × 0.054326,     8 µs/rev
mozilla-central x0000_revs_xx000_added_0_copies       9eec5917337d 67118cc6dcad :    615 revs,  6.831179 s,  0.026815 s,  -6.804364 s, × 0.003925,    43 µs/rev
mozilla-central x0000_revs_xx000_added_x000_copies    f78c615a656c 96a38b690156 :  30263 revs,  3.373551 s,  0.cc85eb s,  -3.170687 s, × 0.060134,     6 µs/rev
mozilla-central x00000_revs_x0000_added_x0000_copies  6832ae71433c 4c222a1d9a00 : 153721 revs, 16.540604 s,  1.219445 s, -15.321159 s, × 0.073724,     7 µs/rev
mozilla-central x00000_revs_x00000_added_x000_copies  76caed42cf7c 1daa622bbe42 : 204976 revs, 21.527155 s,  1.613857 s, -19.913298 s, × 0.074968,     7 µs/rev
mozilla-try     x_revs_x_added_0_copies               aaf6dde0deb8 9790f499805a :      2 revs,  0.084540 s,  0.000873 s,  -0.083667 s, × 0.010326,   436 µs/rev
mozilla-try     x_revs_x000_added_0_copies            d8d0222927b4 5bb8ce8c7450 :      2 revs,  0.507151 s,  0.000885 s,  -0.506266 s, × 0.001745,   442 µs/rev
mozilla-try     x_revs_x_added_x_copies               092fcca11bdb 936255a0384a :      4 revs,  0.021748 s,  0.000161 s,  -0.021587 s, × 0.007403,    40 µs/rev
mozilla-try     x_revs_x00_added_x_copies             b53d2fadbdb5 017afae788ec :      2 revs,  0.236786 s,  0.001138 s,  -0.235648 s, × 0.004806,   568 µs/rev
mozilla-try     x_revs_x000_added_x000_copies         20408ad61ce5 6f0ee96e21ad :      1 revs,  1.111735 s,  0.033399 s,  -1.078336 s, × 0.030042, 33365 µs/rev
mozilla-try     x_revs_x0000_added_x0000_copies       effb563bb7e5 c07a39dc4e80 :      6 revs,  2.228030 s,  0.075445 s,  -2.152585 s, × 0.033862, 12572 µs/rev
mozilla-try     x000_revs_xx00_added_0_copies         6100d773079a 04a55431795e :   1593 revs,  0.091289 s,  0.006456 s,  -0.084833 s, × 0.070720,     4 µs/rev
mozilla-try     x000_revs_x000_added_x_copies         9f17a6fc04f9 2d37b966abed :     41 revs,  0.771361 s,  0.005462 s,  -0.765899 s, × 0.007081,   133 µs/rev
mozilla-try     x000_revs_x000_added_x000_copies      1346fd0130e4 4c65cbdabc1f :   6657 revs,  1.189483 s,  0.064117 s,  -1.125366 s, × 0.053903,     9 µs/rev
mozilla-try     x0000_revs_x_added_0_copies           63519bfd42ee a36a2a865d92 :  40314 revs,  0.089756 s,  0.297563 s,  +0.207807 s, × 3.315244,     7 µs/rev
mozilla-try     x0000_revs_x_added_x_copies           9fe69ff0762d bcabf2a78927 :  38690 revs,  0.084888 s,  0.282463 s,  +0.197575 s, × 3.327479,     7 µs/rev
mozilla-try     x0000_revs_xx000_added_x_copies       156f6e2674f2 4d0f2c178e66 :   8598 revs,  7.682665 s,  0.084038 s,  -7.598627 s, × 0.010939,     9 µs/rev
mozilla-try     x0000_revs_xx000_added_0_copies       9eec5917337d 67118cc6dcad :    615 revs,  6.894680 s,  0.027306 s,  -6.867374 s, × 0.003960,    44 µs/rev
mozilla-try     x0000_revs_xx000_added_x000_copies    89294cd501d9 7ccb2fc7ccb5 :  97052 revs,  7.650907 s,  1.465264 s,  -6.185643 s, × 0.191515,    15 µs/rev
mozilla-try     x0000_revs_x0000_added_x0000_copies   e928c65095ed e951f4ad123a :  52031 revs,  9.898788 s,  0.690376 s,  -9.208412 s, × 0.069743,    13 µs/rev
mozilla-try     x00000_revs_x_added_0_copies          6a320851d377 1ebb79acd503 : 363753 revs,  0.092208 s,  4.011322 s,  +3.919114 s, × 43.50297,    11 µs/rev
mozilla-try     x00000_revs_x00000_added_0_copies     dc8a3ca7010e d16fde900c9c :  34414 revs, 28.130003 s,  0.573541 s, -27.556462 s, × 0.020389,    16 µs/rev
mozilla-try     x00000_revs_x_added_x_copies          5173c4b6f97c 95d83ee7242d : 362229 revs,  0.093366 s,  3.981133 s,  +3.887767 s, × 42.64007,    10 µs/rev
mozilla-try     x00000_revs_x000_added_x_copies       9126823d0e9c ca82787bb23c : 359344 revs,  0.229368 s,  3.996647 s,  +3.767279 s, × 17.42460,    11 µs/rev
mozilla-try     x00000_revs_x0000_added_x0000_copies  8d3fafa80d4b eb884023b810 : 192665 revs, 19.624851 s,  1.520607 s, -18.104244 s, × 0.077484,     7 µs/rev
mozilla-try     x00000_revs_x00000_added_x0000_copies 1b661134e2ca 1ae03d022d6d : 228985 revs, 22.070126 s, 50.244975 s, +28.174849 s, × 2.276606,   219 µs/rev
mozilla-try     x00000_revs_x00000_added_x000_copies  9b2a99adc05e 8e29777b48e6 : 382065 revs, 26.006524 s, 20.030023 s,  -5.976501 s, × 0.770192,    52 µs/rev
private                                                                         : 459513 revs, 18.704612 s, 24.490825 s,  +5.786213 s, × 1.309347,    53 µs/rev

Differential Revision: https://phab.mercurial-scm.org/D9656

Test hiding some commands (which also happens to hide an entire category).

  $ hg --config help.hidden-command.clone=true \
  > --config help.hidden-command.init=true help
  Mercurial Distributed SCM
  
  list of commands:
  
  Remote repository management:
  
   incoming      show new changesets found in source
   outgoing      show changesets not found in the destination
   paths         show aliases for remote repositories
   pull          pull changes from the specified source
   push          push changes to the specified destination
   serve         start stand-alone webserver
  
  Change creation:
  
   commit        commit the specified files or all outstanding changes
  
  Change manipulation:
  
   backout       reverse effect of earlier changeset
   graft         copy changes from other branches onto the current branch
   merge         merge another revision into working directory
  
  Change organization:
  
   bookmarks     create a new bookmark or list existing bookmarks
   branch        set or show the current branch name
   branches      list repository named branches
   phase         set or show the current phase name
   tag           add one or more tags for the current or given revision
   tags          list repository tags
  
  File content management:
  
   annotate      show changeset information by line for each file
   cat           output the current or given revision of files
   copy          mark files as copied for the next commit
   diff          diff repository (or selected files)
   grep          search for a pattern in specified files
  
  Change navigation:
  
   bisect        subdivision search of changesets
   heads         show branch heads
   identify      identify the working directory or specified revision
   log           show revision history of entire repository or files
  
  Working directory management:
  
   add           add the specified files on the next commit
   addremove     add all new files, delete all missing files
   files         list tracked files
   forget        forget the specified files on the next commit
   purge         removes files not tracked by Mercurial
   remove        remove the specified files on the next commit
   rename        rename files; equivalent of copy + remove
   resolve       redo merges or set/view the merge status of files
   revert        restore files to their checkout state
   root          print the root (top) of the current working directory
   shelve        save and set aside changes from the working directory
   status        show changed files in the working directory
   summary       summarize working directory state
   unshelve      restore a shelved change to the working directory
   update        update working directory (or switch revisions)
  
  Change import/export:
  
   archive       create an unversioned archive of a repository revision
   bundle        create a bundle file
   export        dump the header and diffs for one or more changesets
   import        import an ordered set of patches
   unbundle      apply one or more bundle files
  
  Repository maintenance:
  
   manifest      output the current or given revision of the project manifest
   recover       roll back an interrupted transaction
   verify        verify the integrity of the repository
  
  Help:
  
   config        show combined config settings from all hgrc files
   help          show help for a given topic or a help overview
   version       output version and copyright information
  
  additional help topics:
  
  Mercurial identifiers:
  
   filesets      Specifying File Sets
   hgignore      Syntax for Mercurial Ignore Files
   patterns      File Name Patterns
   revisions     Specifying Revisions
   urls          URL Paths
  
  Mercurial output:
  
   color         Colorizing Outputs
   dates         Date Formats
   diffs         Diff Formats
   templating    Template Usage
  
  Mercurial configuration:
  
   config        Configuration Files
   environment   Environment Variables
   extensions    Using Additional Features
   flags         Command-line flags
   hgweb         Configuring hgweb
   merge-tools   Merge Tools
   pager         Pager Support
  
  Concepts:
  
   bundlespec    Bundle File Formats
   glossary      Glossary
   phases        Working with Phases
   subrepos      Subrepositories
  
  Miscellaneous:
  
   deprecated    Deprecated Features
   internals     Technical implementation topics
   scripting     Using Mercurial from scripts and automation
  
  (use 'hg help -v' to show built-in aliases and global options)

Test hiding some topics.

  $ hg --config help.hidden-topic.deprecated=true \
  > --config help.hidden-topic.internals=true \
  > --config help.hidden-topic.scripting=true help
  Mercurial Distributed SCM
  
  list of commands:
  
  Repository creation:
  
   clone         make a copy of an existing repository
   init          create a new repository in the given directory
  
  Remote repository management:
  
   incoming      show new changesets found in source
   outgoing      show changesets not found in the destination
   paths         show aliases for remote repositories
   pull          pull changes from the specified source
   push          push changes to the specified destination
   serve         start stand-alone webserver
  
  Change creation:
  
   commit        commit the specified files or all outstanding changes
  
  Change manipulation:
  
   backout       reverse effect of earlier changeset
   graft         copy changes from other branches onto the current branch
   merge         merge another revision into working directory
  
  Change organization:
  
   bookmarks     create a new bookmark or list existing bookmarks
   branch        set or show the current branch name
   branches      list repository named branches
   phase         set or show the current phase name
   tag           add one or more tags for the current or given revision
   tags          list repository tags
  
  File content management:
  
   annotate      show changeset information by line for each file
   cat           output the current or given revision of files
   copy          mark files as copied for the next commit
   diff          diff repository (or selected files)
   grep          search for a pattern in specified files
  
  Change navigation:
  
   bisect        subdivision search of changesets
   heads         show branch heads
   identify      identify the working directory or specified revision
   log           show revision history of entire repository or files
  
  Working directory management:
  
   add           add the specified files on the next commit
   addremove     add all new files, delete all missing files
   files         list tracked files
   forget        forget the specified files on the next commit
   purge         removes files not tracked by Mercurial
   remove        remove the specified files on the next commit
   rename        rename files; equivalent of copy + remove
   resolve       redo merges or set/view the merge status of files
   revert        restore files to their checkout state
   root          print the root (top) of the current working directory
   shelve        save and set aside changes from the working directory
   status        show changed files in the working directory
   summary       summarize working directory state
   unshelve      restore a shelved change to the working directory
   update        update working directory (or switch revisions)
  
  Change import/export:
  
   archive       create an unversioned archive of a repository revision
   bundle        create a bundle file
   export        dump the header and diffs for one or more changesets
   import        import an ordered set of patches
   unbundle      apply one or more bundle files
  
  Repository maintenance:
  
   manifest      output the current or given revision of the project manifest
   recover       roll back an interrupted transaction
   verify        verify the integrity of the repository
  
  Help:
  
   config        show combined config settings from all hgrc files
   help          show help for a given topic or a help overview
   version       output version and copyright information
  
  additional help topics:
  
  Mercurial identifiers:
  
   filesets      Specifying File Sets
   hgignore      Syntax for Mercurial Ignore Files
   patterns      File Name Patterns
   revisions     Specifying Revisions
   urls          URL Paths
  
  Mercurial output:
  
   color         Colorizing Outputs
   dates         Date Formats
   diffs         Diff Formats
   templating    Template Usage
  
  Mercurial configuration:
  
   config        Configuration Files
   environment   Environment Variables
   extensions    Using Additional Features
   flags         Command-line flags
   hgweb         Configuring hgweb
   merge-tools   Merge Tools
   pager         Pager Support
  
  Concepts:
  
   bundlespec    Bundle File Formats
   glossary      Glossary
   phases        Working with Phases
   subrepos      Subrepositories
  
  (use 'hg help -v' to show built-in aliases and global options)