copies-rust: parse the changed-file sidedata directly in rust It does not make much sense to parse the data into python object using slow python code to later turn them into rust object. We directly pass the binary blob and use it directly in Rust. Ideally we could directly read the sidedata in Rust, using a revlog in Rust. However we do not have this ready to use yet. This more direct approach provides a nice speedup over the board. Especially five cases that we previously too slow to return in the previous changeset are not able to finish. Notably, we are now significantly faster than the Python version of this code in all the meaningful cases. I looked at the various cases that remains significantly slower then the filelog version and they are currently 3 main source of slowness: * The isancestor computation: even if we cache them, if the revs spawn over a large amount of history the ancestry checking is still quite expensive. Using a different approach more centered on the graph we are currently considering might yield significant speed. * Merging of the map from the two parents: in some case, this climb up to ⅔ of the time spent in copy tracing. See inline comment for idea to handle this better. * Extracting data from the filelog. I would like to think this mostly comes from the fact my test repositories pre-date Valentin Gatien-Baron improvement of the `files` field (99ebde4fec99) and that more recent revisions will be faster to fetch. Further testing on this aspect is needed. This revision compared to the previous one: =========================================== 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, 0.000047 s, 0.000049 s, +0.000002 s, × 1.0426, 49 µs/rev mercurial x_revs_x_added_x_copies 2b1c78674230 0c1d10351869 : 6 revs, 0.000181 s, 0.000114 s, -0.000067 s, × 0.6298, 19 µs/rev mercurial x000_revs_x000_added_x_copies 81f8ff2a9bf2 dd3267698d84 : 1032 revs, 0.005852 s, 0.004223 s, -0.001629 s, × 0.7216, 4 µs/rev pypy x_revs_x_added_0_copies aed021ee8ae8 099ed31b181b : 9 revs, 0.000229 s, 0.000305 s, +0.000076 s, × 1.3319, 33 µs/rev pypy x_revs_x000_added_0_copies 4aa4e1f8e19a 359343b9ac0e : 1 revs, 0.000058 s, 0.000060 s, +0.000002 s, × 1.0345, 60 µs/rev pypy x_revs_x_added_x_copies ac52eb7bbbb0 72e022663155 : 7 revs, 0.000146 s, 0.000173 s, +0.000027 s, × 1.1849, 24 µs/rev pypy x_revs_x00_added_x_copies c3b14617fbd7 ace7255d9a26 : 1 revs, 0.001206 s, 0.000446 s, -0.000760 s, × 0.3698, 446 µs/rev pypy x_revs_x000_added_x000_copies df6f7a526b60 a83dc6a2d56f : 6 revs, 0.025275 s, 0.010360 s, -0.014915 s, × 0.4099, 1726 µs/rev pypy x000_revs_xx00_added_0_copies 89a76aede314 2f22446ff07e : 4785 revs, 0.080303 s, 0.048002 s, -0.032301 s, × 0.5978, 10 µs/rev pypy x000_revs_x000_added_x_copies 8a3b5bfd266e 2c68e87c3efe : 6780 revs, 0.152641 s, 0.075705 s, -0.076936 s, × 0.4960, 11 µs/rev pypy x000_revs_x000_added_x000_copies 89a76aede314 7b3dda341c84 : 5441 revs, 0.099107 s, 0.056705 s, -0.042402 s, × 0.5722, 10 µs/rev pypy x0000_revs_x_added_0_copies d1defd0dc478 c9cb1334cc78 : 43646 revs, 2.137894 s, 0.794685 s, -1.343209 s, × 0.3717, 18 µs/rev pypy x0000_revs_xx000_added_0_copies bf2c629d0071 4ffed77c095c : 26389 revs, 0.022202 s, 0.020209 s, -0.001993 s, × 0.9102, 0 µs/rev pypy x0000_revs_xx000_added_x000_copies 08ea3258278e d9fa043f30c0 : 11316 revs, 0.228946 s, 0.122475 s, -0.106471 s, × 0.5350, 10 µs/rev netbeans x_revs_x_added_0_copies fb0955ffcbcd a01e9239f9e7 : 2 revs, 0.000186 s, 0.000142 s, -0.000044 s, × 0.7634, 71 µs/rev netbeans x_revs_x000_added_0_copies 6f360122949f 20eb231cc7d0 : 2 revs, 0.000133 s, 0.000113 s, -0.000020 s, × 0.8496, 56 µs/rev netbeans x_revs_x_added_x_copies 1ada3faf6fb6 5a39d12eecf4 : 3 revs, 0.000320 s, 0.000241 s, -0.000079 s, × 0.7531, 80 µs/rev netbeans x_revs_x00_added_x_copies 35be93ba1e2c 9eec5e90c05f : 9 revs, 0.001339 s, 0.000729 s, -0.000610 s, × 0.5444, 81 µs/rev netbeans x000_revs_xx00_added_0_copies eac3045b4fdd 51d4ae7f1290 : 1421 revs, 0.015694 s, 0.010198 s, -0.005496 s, × 0.6498, 7 µs/rev netbeans x000_revs_x000_added_x_copies e2063d266acd 6081d72689dc : 1533 revs, 0.018457 s, 0.015312 s, -0.003145 s, × 0.8296, 9 µs/rev netbeans x000_revs_x000_added_x000_copies ff453e9fee32 411350406ec2 : 5750 revs, 0.111691 s, 0.060517 s, -0.051174 s, × 0.5418, 10 µs/rev netbeans x0000_revs_xx000_added_x000_copies 588c2d1ced70 1aad62e59ddd : 67005 revs, 1.166017 s, 0.611102 s, -0.554915 s, × 0.5241, 9 µs/rev mozilla-central x_revs_x_added_0_copies 3697f962bb7b 7015fcdd43a2 : 2 revs, 0.000197 s, 0.000164 s, -0.000033 s, × 0.8325, 82 µs/rev mozilla-central x_revs_x000_added_0_copies dd390860c6c9 40d0c5bed75d : 8 revs, 0.000626 s, 0.000334 s, -0.000292 s, × 0.5335, 41 µs/rev mozilla-central x_revs_x_added_x_copies 8d198483ae3b 14207ffc2b2f : 9 revs, 0.000303 s, 0.000463 s, +0.000160 s, × 1.5281, 51 µs/rev mozilla-central x_revs_x00_added_x_copies 98cbc58cc6bc 446a150332c3 : 7 revs, 0.001679 s, 0.000730 s, -0.000949 s, × 0.4348, 104 µs/rev mozilla-central x_revs_x000_added_x000_copies 3c684b4b8f68 0a5e72d1b479 : 3 revs, 0.006947 s, 0.003522 s, -0.003425 s, × 0.5070, 1174 µs/rev mozilla-central x_revs_x0000_added_x0000_copies effb563bb7e5 c07a39dc4e80 : 6 revs, 0.133070 s, 0.072518 s, -0.060552 s, × 0.5450, 12086 µs/rev mozilla-central x000_revs_xx00_added_0_copies 6100d773079a 04a55431795e : 1593 revs, 0.008705 s, 0.005760 s, -0.002945 s, × 0.6617, 3 µs/rev mozilla-central x000_revs_x000_added_x_copies 9f17a6fc04f9 2d37b966abed : 8315 revs, 0.005913 s, 0.005720 s, -0.000193 s, × 0.9674, 0 µs/rev mozilla-central x000_revs_x000_added_x000_copies 7c97034feb78 4407bd0c6330 : 7839 revs, 0.101373 s, 0.063310 s, -0.038063 s, × 0.6245, 8 µs/rev mozilla-central x0000_revs_xx000_added_0_copies 9eec5917337d 67118cc6dcad : 45299 revs, 0.046526 s, 0.043608 s, -0.002918 s, × 0.9373, 0 µs/rev mozilla-central x0000_revs_xx000_added_x000_copies f78c615a656c 96a38b690156 : 30263 revs, 0.313954 s, 0.204831 s, -0.109123 s, × 0.6524, 6 µs/rev mozilla-central x00000_revs_x0000_added_x0000_copies 6832ae71433c 4c222a1d9a00 : 153721 revs, 3.367395 s, 2.161906 s, -1.205489 s, × 0.6420, 14 µs/rev mozilla-central x00000_revs_x00000_added_x000_copies 76caed42cf7c 1daa622bbe42 : 210546 revs, 4.691820 s, 3.291831 s, -1.399989 s, × 0.7016, 15 µs/rev mozilla-try x_revs_x_added_0_copies aaf6dde0deb8 9790f499805a : 2 revs, 0.001199 s, 0.001213 s, +0.000014 s, × 1.0117, 606 µs/rev mozilla-try x_revs_x000_added_0_copies d8d0222927b4 5bb8ce8c7450 : 2 revs, 0.001216 s, 0.001225 s, +0.000009 s, × 1.0074, 612 µs/rev mozilla-try x_revs_x_added_x_copies 092fcca11bdb 936255a0384a : 4 revs, 0.000613 s, 0.000564 s, -0.000049 s, × 0.9201, 141 µs/rev mozilla-try x_revs_x00_added_x_copies b53d2fadbdb5 017afae788ec : 2 revs, 0.001906 s, 0.001549 s, -0.000357 s, × 0.8127, 774 µs/rev mozilla-try x_revs_x000_added_x000_copies 20408ad61ce5 6f0ee96e21ad : 1 revs, 0.092766 s, 0.035918 s, -0.056848 s, × 0.3872, 35918 µs/rev mozilla-try x_revs_x0000_added_x0000_copies effb563bb7e5 c07a39dc4e80 : 6 revs, 0.136074 s, 0.073788 s, -0.062286 s, × 0.5423, 12298 µs/rev mozilla-try x000_revs_xx00_added_0_copies 6100d773079a 04a55431795e : 1593 revs, 0.009067 s, 0.006151 s, -0.002916 s, × 0.6784, 3 µs/rev mozilla-try x000_revs_x000_added_x_copies 9f17a6fc04f9 2d37b966abed : 8315 revs, 0.006243 s, 0.006165 s, -0.000078 s, × 0.9875, 0 µs/rev mozilla-try x000_revs_x000_added_x000_copies 1346fd0130e4 4c65cbdabc1f : 6657 revs, 0.114463 s, 0.065421 s, -0.049042 s, × 0.5715, 9 µs/rev mozilla-try x0000_revs_x_added_0_copies 63519bfd42ee a36a2a865d92 : 40314 revs, 0.433683 s, 0.313749 s, -0.119934 s, × 0.7235, 7 µs/rev mozilla-try x0000_revs_x_added_x_copies 9fe69ff0762d bcabf2a78927 : 38690 revs, 0.411278 s, 0.297867 s, -0.113411 s, × 0.7242, 7 µs/rev mozilla-try x0000_revs_xx000_added_x_copies 156f6e2674f2 4d0f2c178e66 : 54487 revs, 0.155133 s, 0.111300 s, -0.043833 s, × 0.7174, 2 µs/rev mozilla-try x0000_revs_xx000_added_0_copies 9eec5917337d 67118cc6dcad : 45299 revs, 0.048933 s, 0.046202 s, -0.002731 s, × 0.9442, 1 µs/rev mozilla-try x0000_revs_xx000_added_x000_copies 89294cd501d9 7ccb2fc7ccb5 : 97052 revs, 8.100385 s, 1.999640 s, -6.100745 s, × 0.2469, 20 µs/rev mozilla-try x0000_revs_x0000_added_x0000_copies e928c65095ed e951f4ad123a : 52031 revs, 1.446720 s, 0.809134 s, -0.637586 s, × 0.5593, 15 µs/rev mozilla-try x00000_revs_x_added_0_copies 6a320851d377 1ebb79acd503 : 363753 revs, killed , 47.406785 s, , , 130 µs/rev mozilla-try x00000_revs_x00000_added_0_copies dc8a3ca7010e d16fde900c9c : 444327 revs, 1.369537 s, 0.996219 s, -0.373318 s, × 0.7274, 2 µs/rev mozilla-try x00000_revs_x_added_x_copies 5173c4b6f97c 95d83ee7242d : 362229 revs, killed , 47.273399 s, , , 130 µs/rev mozilla-try x00000_revs_x000_added_x_copies 9126823d0e9c ca82787bb23c : 359344 revs, killed , 47.419099 s, , , 131 µs/rev mozilla-try x00000_revs_x0000_added_x0000_copies 8d3fafa80d4b eb884023b810 : 192665 revs, 5.186079 s, 3.512653 s, -1.673426 s, × 0.6773, 18 µs/rev mozilla-try x00000_revs_x00000_added_x0000_copies 1b661134e2ca 1ae03d022d6d : 237259 revs, killed , 44.459049 s, , , 187 µs/rev mozilla-try x00000_revs_x00000_added_x000_copies 9b2a99adc05e 8e29777b48e6 : 391148 revs, killed , 52.837926 s, , , 135 µs/rev This revision compared to the python code: ========================================== Repo Case Source-Rev Dest-Rev # of revisions Python-Time Rust-Time Difference Factor time per rev -------------------------------------------------------------------------------------------------------------------------------------------------------------- mercurial x_revs_x_added_0_copies ad6b123de1c7 39cfcef4f463 : 1 revs, 0.000044 s, 0.000049 s, +0.000005 s, × 1.1136, 49 µs/rev mercurial x_revs_x_added_x_copies 2b1c78674230 0c1d10351869 : 6 revs, 0.000138 s, 0.000114 s, -0.000024 s, × 0.8261, 19 µs/rev mercurial x000_revs_x000_added_x_copies 81f8ff2a9bf2 dd3267698d84 : 1032 revs, 0.005052 s, 0.004223 s, -0.000829 s, × 0.8359, 4 µs/rev pypy x_revs_x_added_0_copies aed021ee8ae8 099ed31b181b : 9 revs, 0.000219 s, 0.000305 s, +0.000086 s, × 1.3927, 33 µs/rev pypy x_revs_x000_added_0_copies 4aa4e1f8e19a 359343b9ac0e : 1 revs, 0.000055 s, 0.000060 s, +0.000005 s, × 1.0909, 60 µs/rev pypy x_revs_x_added_x_copies ac52eb7bbbb0 72e022663155 : 7 revs, 0.000128 s, 0.000173 s, +0.000045 s, × 1.3516, 24 µs/rev pypy x_revs_x00_added_x_copies c3b14617fbd7 ace7255d9a26 : 1 revs, 0.001089 s, 0.000446 s, -0.000643 s, × 0.4096, 446 µs/rev pypy x_revs_x000_added_x000_copies df6f7a526b60 a83dc6a2d56f : 6 revs, 0.017407 s, 0.010360 s, -0.007047 s, × 0.5952, 1726 µs/rev pypy x000_revs_xx00_added_0_copies 89a76aede314 2f22446ff07e : 4785 revs, 0.094175 s, 0.048002 s, -0.046173 s, × 0.5097, 10 µs/rev pypy x000_revs_x000_added_x_copies 8a3b5bfd266e 2c68e87c3efe : 6780 revs, 0.238009 s, 0.075705 s, -0.162304 s, × 0.3181, 11 µs/rev pypy x000_revs_x000_added_x000_copies 89a76aede314 7b3dda341c84 : 5441 revs, 0.125876 s, 0.056705 s, -0.069171 s, × 0.4505, 10 µs/rev pypy x0000_revs_x_added_0_copies d1defd0dc478 c9cb1334cc78 : 43646 revs, 3.581556 s, 0.794685 s, -2.786871 s, × 0.2219, 18 µs/rev pypy x0000_revs_xx000_added_0_copies bf2c629d0071 4ffed77c095c : 26389 revs, 0.016721 s, 0.020209 s, +0.003488 s, × 1.2086, 0 µs/rev pypy x0000_revs_xx000_added_x000_copies 08ea3258278e d9fa043f30c0 : 11316 revs, 0.242367 s, 0.122475 s, -0.119892 s, × 0.5053, 10 µs/rev netbeans x_revs_x_added_0_copies fb0955ffcbcd a01e9239f9e7 : 2 revs, 0.000165 s, 0.000142 s, -0.000023 s, × 0.8606, 71 µs/rev netbeans x_revs_x000_added_0_copies 6f360122949f 20eb231cc7d0 : 2 revs, 0.000114 s, 0.000113 s, -0.000001 s, × 0.9912, 56 µs/rev netbeans x_revs_x_added_x_copies 1ada3faf6fb6 5a39d12eecf4 : 3 revs, 0.000296 s, 0.000241 s, -0.000055 s, × 0.8142, 80 µs/rev netbeans x_revs_x00_added_x_copies 35be93ba1e2c 9eec5e90c05f : 9 revs, 0.001124 s, 0.000729 s, -0.000395 s, × 0.6486, 81 µs/rev netbeans x000_revs_xx00_added_0_copies eac3045b4fdd 51d4ae7f1290 : 1421 revs, 0.013060 s, 0.010198 s, -0.002862 s, × 0.7809, 7 µs/rev netbeans x000_revs_x000_added_x_copies e2063d266acd 6081d72689dc : 1533 revs, 0.017112 s, 0.015312 s, -0.001800 s, × 0.8948, 9 µs/rev netbeans x000_revs_x000_added_x000_copies ff453e9fee32 411350406ec2 : 5750 revs, 0.660350 s, 0.060517 s, -0.599833 s, × 0.0916, 10 µs/rev netbeans x0000_revs_xx000_added_x000_copies 588c2d1ced70 1aad62e59ddd : 67005 revs, 10.032499 s, 0.611102 s, -9.421397 s, × 0.0609, 9 µs/rev mozilla-central x_revs_x_added_0_copies 3697f962bb7b 7015fcdd43a2 : 2 revs, 0.000189 s, 0.000164 s, -0.000025 s, × 0.8677, 82 µs/rev mozilla-central x_revs_x000_added_0_copies dd390860c6c9 40d0c5bed75d : 8 revs, 0.000462 s, 0.000334 s, -0.000128 s, × 0.7229, 41 µs/rev mozilla-central x_revs_x_added_x_copies 8d198483ae3b 14207ffc2b2f : 9 revs, 0.000270 s, 0.000463 s, +0.000193 s, × 1.7148, 51 µs/rev mozilla-central x_revs_x00_added_x_copies 98cbc58cc6bc 446a150332c3 : 7 revs, 0.001474 s, 0.000730 s, -0.000744 s, × 0.4953, 104 µs/rev mozilla-central x_revs_x000_added_x000_copies 3c684b4b8f68 0a5e72d1b479 : 3 revs, 0.004806 s, 0.003522 s, -0.001284 s, × 0.7328, 1174 µs/rev mozilla-central x_revs_x0000_added_x0000_copies effb563bb7e5 c07a39dc4e80 : 6 revs, 0.085150 s, 0.072518 s, -0.012632 s, × 0.8517, 12086 µs/rev mozilla-central x000_revs_xx00_added_0_copies 6100d773079a 04a55431795e : 1593 revs, 0.007064 s, 0.005760 s, -0.001304 s, × 0.8154, 3 µs/rev mozilla-central x000_revs_x000_added_x_copies 9f17a6fc04f9 2d37b966abed : 8315 revs, 0.004741 s, 0.005720 s, +0.000979 s, × 1.2065, 0 µs/rev mozilla-central x000_revs_x000_added_x000_copies 7c97034feb78 4407bd0c6330 : 7839 revs, 0.190133 s, 0.063310 s, -0.126823 s, × 0.3330, 8 µs/rev mozilla-central x0000_revs_xx000_added_0_copies 9eec5917337d 67118cc6dcad : 45299 revs, 0.035651 s, 0.043608 s, +0.007957 s, × 1.2232, 0 µs/rev mozilla-central x0000_revs_xx000_added_x000_copies f78c615a656c 96a38b690156 : 30263 revs, 0.440694 s, 0.204831 s, -0.235863 s, × 0.4648, 6 µs/rev mozilla-central x00000_revs_x0000_added_x0000_copies 6832ae71433c 4c222a1d9a00 : 153721 revs, 18.454163 s, 2.161906 s, -16.292257 s, × 0.1172, 14 µs/rev mozilla-central x00000_revs_x00000_added_x000_copies 76caed42cf7c 1daa622bbe42 : 210546 revs, 31.562719 s, 3.291831 s, -28.270888 s, × 0.1043, 15 µs/rev mozilla-try x_revs_x_added_0_copies aaf6dde0deb8 9790f499805a : 2 revs, 0.001189 s, 0.001213 s, +0.000024 s, × 1.0202, 606 µs/rev mozilla-try x_revs_x000_added_0_copies d8d0222927b4 5bb8ce8c7450 : 2 revs, 0.001204 s, 0.001225 s, +0.000021 s, × 1.0174, 612 µs/rev mozilla-try x_revs_x_added_x_copies 092fcca11bdb 936255a0384a : 4 revs, 0.000586 s, 0.000564 s, -0.000022 s, × 0.9625, 141 µs/rev mozilla-try x_revs_x00_added_x_copies b53d2fadbdb5 017afae788ec : 2 revs, 0.001845 s, 0.001549 s, -0.000296 s, × 0.8396, 774 µs/rev mozilla-try x_revs_x000_added_x000_copies 20408ad61ce5 6f0ee96e21ad : 1 revs, 0.063822 s, 0.035918 s, -0.027904 s, × 0.5628, 35918 µs/rev mozilla-try x_revs_x0000_added_x0000_copies effb563bb7e5 c07a39dc4e80 : 6 revs, 0.088038 s, 0.073788 s, -0.014250 s, × 0.8381, 12298 µs/rev mozilla-try x000_revs_xx00_added_0_copies 6100d773079a 04a55431795e : 1593 revs, 0.007389 s, 0.006151 s, -0.001238 s, × 0.8325, 3 µs/rev mozilla-try x000_revs_x000_added_x_copies 9f17a6fc04f9 2d37b966abed : 8315 revs, 0.004868 s, 0.006165 s, +0.001297 s, × 1.2664, 0 µs/rev mozilla-try x000_revs_x000_added_x000_copies 1346fd0130e4 4c65cbdabc1f : 6657 revs, 0.222450 s, 0.065421 s, -0.157029 s, × 0.2941, 9 µs/rev mozilla-try x0000_revs_x_added_0_copies 63519bfd42ee a36a2a865d92 : 40314 revs, 0.370675 s, 0.313749 s, -0.056926 s, × 0.8464, 7 µs/rev mozilla-try x0000_revs_x_added_x_copies 9fe69ff0762d bcabf2a78927 : 38690 revs, 0.358020 s, 0.297867 s, -0.060153 s, × 0.8320, 7 µs/rev mozilla-try x0000_revs_xx000_added_x_copies 156f6e2674f2 4d0f2c178e66 : 54487 revs, 0.145235 s, 0.111300 s, -0.033935 s, × 0.7663, 2 µs/rev mozilla-try x0000_revs_xx000_added_0_copies 9eec5917337d 67118cc6dcad : 45299 revs, 0.037606 s, 0.046202 s, +0.008596 s, × 1.2286, 1 µs/rev mozilla-try x0000_revs_xx000_added_x000_copies 89294cd501d9 7ccb2fc7ccb5 : 97052 revs, 7.382439 s, 1.999640 s, -5.382799 s, × 0.2709, 20 µs/rev mozilla-try x0000_revs_x0000_added_x0000_copies e928c65095ed e951f4ad123a : 52031 revs, 7.273506 s, 0.809134 s, -6.464372 s, × 0.1112, 15 µs/rev mozilla-try x00000_revs_x_added_0_copies 6a320851d377 1ebb79acd503 : 363753 revs, killed , 47.406785 s, , , 130 µs/rev mozilla-try x00000_revs_x00000_added_0_copies dc8a3ca7010e d16fde900c9c : 444327 revs, 1.074593 s, 0.996219 s, -0.078374 s, × 0.9271, 2 µs/rev mozilla-try x00000_revs_x_added_x_copies 5173c4b6f97c 95d83ee7242d : 362229 revs, killed , 47.273399 s, , , 130 µs/rev mozilla-try x00000_revs_x000_added_x_copies 9126823d0e9c ca82787bb23c : 359344 revs, killed , 47.419099 s, , , 131 µs/rev mozilla-try x00000_revs_x0000_added_x0000_copies 8d3fafa80d4b eb884023b810 : 192665 revs, 27.746195 s, 3.512653 s, -24.233542 s, × 0.1266, 18 µs/rev mozilla-try x00000_revs_x00000_added_x0000_copies 1b661134e2ca 1ae03d022d6d : 237259 revs, killed , 44.459049 s, , , 187 µs/rev mozilla-try x00000_revs_x00000_added_x000_copies 9b2a99adc05e 8e29777b48e6 : 391148 revs, killed , 52.837926 s, , , 135 µs/rev This revision compared to the filelog algorithm: ================================================ Repo Case Source-Rev Dest-Rev # of revisions filelog sidedata Difference Factor time per rev -------------------------------------------------------------------------------------------------------------------------------------------------------------- mercurial x_revs_x_added_0_copies ad6b123de1c7 39cfcef4f463 : 1 revs, 0.000906 s, 0.000049 s, -0.000857 s, × 0.0540, 48 µs/rev mercurial x_revs_x_added_x_copies 2b1c78674230 0c1d10351869 : 6 revs, 0.001844 s, 0.000114 s, -0.001730 s, × 0.0618, 18 µs/rev mercurial x000_revs_x000_added_x_copies 81f8ff2a9bf2 dd3267698d84 : 1032 revs, 0.018577 s, 0.004223 s, -0.014354 s, × 0.2273, 4 µs/rev pypy x_revs_x_added_0_copies aed021ee8ae8 099ed31b181b : 9 revs, 0.005009 s, 0.000305 s, -0.004704 s, × 0.0608, 33 µs/rev pypy x_revs_x000_added_0_copies 4aa4e1f8e19a 359343b9ac0e : 1 revs, 0.209606 s, 0.000060 s, -0.209546 s, × 0.0002, 59 µs/rev pypy x_revs_x_added_x_copies ac52eb7bbbb0 72e022663155 : 7 revs, 0.017008 s, 0.000173 s, -0.016835 s, × 0.0101, 24 µs/rev pypy x_revs_x00_added_x_copies c3b14617fbd7 ace7255d9a26 : 1 revs, 0.019227 s, 0.000446 s, -0.018781 s, × 0.0231, 445 µs/rev pypy x_revs_x000_added_x000_copies df6f7a526b60 a83dc6a2d56f : 6 revs, 0.765782 s, 0.010360 s, -0.755422 s, × 0.0135, 1726 µs/rev pypy x000_revs_xx00_added_0_copies 89a76aede314 2f22446ff07e : 4785 revs, 1.186068 s, 0.048002 s, -1.138066 s, × 0.0404, 10 µs/rev pypy x000_revs_x000_added_x_copies 8a3b5bfd266e 2c68e87c3efe : 6780 revs, 1.266745 s, 0.075705 s, -1.191040 s, × 0.0597, 11 µs/rev pypy x000_revs_x000_added_x000_copies 89a76aede314 7b3dda341c84 : 5441 revs, 1.666389 s, 0.056705 s, -1.609684 s, × 0.0340, 10 µs/rev pypy x0000_revs_x_added_0_copies d1defd0dc478 c9cb1334cc78 : 43646 revs, 0.001070 s, 0.794685 s, +0.793615 s, × 742.69, 18 µs/rev pypy x0000_revs_xx000_added_0_copies bf2c629d0071 4ffed77c095c : 26389 revs, 1.076269 s, 0.020209 s, -1.056060 s, × 0.0187, 0 µs/rev pypy x0000_revs_xx000_added_x000_copies 08ea3258278e d9fa043f30c0 : 11316 revs, 1.355085 s, 0.122475 s, -1.232610 s, × 0.0903, 10 µs/rev netbeans x_revs_x_added_0_copies fb0955ffcbcd a01e9239f9e7 : 2 revs, 0.028551 s, 0.000142 s, -0.028409 s, × 0.0049, 70 µs/rev netbeans x_revs_x000_added_0_copies 6f360122949f 20eb231cc7d0 : 2 revs, 0.157319 s, 0.000113 s, -0.157206 s, × 0.0007, 56 µs/rev netbeans x_revs_x_added_x_copies 1ada3faf6fb6 5a39d12eecf4 : 3 revs, 0.025722 s, 0.000241 s, -0.025481 s, × 0.0093, 80 µs/rev netbeans x_revs_x00_added_x_copies 35be93ba1e2c 9eec5e90c05f : 9 revs, 0.053374 s, 0.000729 s, -0.052645 s, × 0.0136, 80 µs/rev netbeans x000_revs_xx00_added_0_copies eac3045b4fdd 51d4ae7f1290 : 1421 revs, 0.038146 s, 0.010198 s, -0.027948 s, × 0.2673, 7 µs/rev netbeans x000_revs_x000_added_x_copies e2063d266acd 6081d72689dc : 1533 revs, 0.229215 s, 0.015312 s, -0.213903 s, × 0.0668, 9 µs/rev netbeans x000_revs_x000_added_x000_copies ff453e9fee32 411350406ec2 : 5750 revs, 0.974484 s, 0.060517 s, -0.913967 s, × 0.0621, 10 µs/rev netbeans x0000_revs_xx000_added_x000_copies 588c2d1ced70 1aad62e59ddd : 67005 revs, 3.924308 s, 0.611102 s, -3.313206 s, × 0.1557, 9 µs/rev mozilla-central x_revs_x_added_0_copies 3697f962bb7b 7015fcdd43a2 : 2 revs, 0.035563 s, 0.000164 s, -0.035399 s, × 0.0046, 81 µs/rev mozilla-central x_revs_x000_added_0_copies dd390860c6c9 40d0c5bed75d : 8 revs, 0.145766 s, 0.000334 s, -0.145432 s, × 0.0022, 41 µs/rev mozilla-central x_revs_x_added_x_copies 8d198483ae3b 14207ffc2b2f : 9 revs, 0.026283 s, 0.000463 s, -0.025820 s, × 0.0176, 51 µs/rev mozilla-central x_revs_x00_added_x_copies 98cbc58cc6bc 446a150332c3 : 7 revs, 0.087403 s, 0.000730 s, -0.086673 s, × 0.0083, 104 µs/rev mozilla-central x_revs_x000_added_x000_copies 3c684b4b8f68 0a5e72d1b479 : 3 revs, 0.209484 s, 0.003522 s, -0.205962 s, × 0.0168, 1173 µs/rev mozilla-central x_revs_x0000_added_x0000_copies effb563bb7e5 c07a39dc4e80 : 6 revs, 2.197867 s, 0.072518 s, -2.125349 s, × 0.0329, 12084 µs/rev mozilla-central x000_revs_xx00_added_0_copies 6100d773079a 04a55431795e : 1593 revs, 0.090142 s, 0.005760 s, -0.084382 s, × 0.0638, 3 µs/rev mozilla-central x000_revs_x000_added_x_copies 9f17a6fc04f9 2d37b966abed : 8315 revs, 0.742658 s, 0.005720 s, -0.736938 s, × 0.0077, 0 µs/rev mozilla-central x000_revs_x000_added_x000_copies 7c97034feb78 4407bd0c6330 : 7839 revs, 1.166159 s, 0.063310 s, -1.102849 s, × 0.0542, 8 µs/rev mozilla-central x0000_revs_xx000_added_0_copies 9eec5917337d 67118cc6dcad : 45299 revs, 6.721719 s, 0.043608 s, -6.678111 s, × 0.0064, 0 µs/rev mozilla-central x0000_revs_xx000_added_x000_copies f78c615a656c 96a38b690156 : 30263 revs, 3.356523 s, 0.204831 s, -3.151692 s, × 0.0610, 6 µs/rev mozilla-central x00000_revs_x0000_added_x0000_copies 6832ae71433c 4c222a1d9a00 : 153721 revs, 15.880822 s, 2.161906 s, -13.718916 s, × 0.1361, 14 µs/rev mozilla-central x00000_revs_x00000_added_x000_copies 76caed42cf7c 1daa622bbe42 : 210546 revs, 20.781275 s, 3.291831 s, -17.489444 s, × 0.1584, 15 µs/rev mozilla-try x_revs_x_added_0_copies aaf6dde0deb8 9790f499805a : 2 revs, 0.084165 s, 0.001213 s, -0.082952 s, × 0.0144, 606 µs/rev mozilla-try x_revs_x000_added_0_copies d8d0222927b4 5bb8ce8c7450 : 2 revs, 0.503744 s, 0.001225 s, -0.502519 s, × 0.0024, 612 µs/rev mozilla-try x_revs_x_added_x_copies 092fcca11bdb 936255a0384a : 4 revs, 0.021545 s, 0.000564 s, -0.020981 s, × 0.0261, 140 µs/rev mozilla-try x_revs_x00_added_x_copies b53d2fadbdb5 017afae788ec : 2 revs, 0.240699 s, 0.001549 s, -0.239150 s, × 0.0064, 774 µs/rev mozilla-try x_revs_x000_added_x000_copies 20408ad61ce5 6f0ee96e21ad : 1 revs, 1.100682 s, 0.035918 s, -1.064764 s, × 0.0326, 35882 µs/rev mozilla-try x_revs_x0000_added_x0000_copies effb563bb7e5 c07a39dc4e80 : 6 revs, 2.234809 s, 0.073788 s, -2.161021 s, × 0.0330, 12295 µs/rev mozilla-try x000_revs_xx00_added_0_copies 6100d773079a 04a55431795e : 1593 revs, 0.091222 s, 0.006151 s, -0.085071 s, × 0.0674, 3 µs/rev mozilla-try x000_revs_x000_added_x_copies 9f17a6fc04f9 2d37b966abed : 8315 revs, 0.764722 s, 0.006165 s, -0.758557 s, × 0.0080, 0 µs/rev mozilla-try x000_revs_x000_added_x000_copies 1346fd0130e4 4c65cbdabc1f : 6657 revs, 1.185655 s, 0.065421 s, -1.120234 s, × 0.0551, 9 µs/rev mozilla-try x0000_revs_x_added_0_copies 63519bfd42ee a36a2a865d92 : 40314 revs, 0.089736 s, 0.313749 s, +0.224013 s, × 3.4963, 7 µs/rev mozilla-try x0000_revs_x_added_x_copies 9fe69ff0762d bcabf2a78927 : 38690 revs, 0.084132 s, 0.297867 s, +0.213735 s, × 3.5404, 7 µs/rev mozilla-try x0000_revs_xx000_added_x_copies 156f6e2674f2 4d0f2c178e66 : 54487 revs, 7.581932 s, 0.111300 s, -7.470632 s, × 0.0146, 2 µs/rev mozilla-try x0000_revs_xx000_added_0_copies 9eec5917337d 67118cc6dcad : 45299 revs, 6.671144 s, 0.046202 s, -6.624942 s, × 0.0069, 1 µs/rev mozilla-try x0000_revs_xx000_added_x000_copies 89294cd501d9 7ccb2fc7ccb5 : 97052 revs, 7.674771 s, 1.999640 s, -5.675131 s, × 0.2605, 20 µs/rev mozilla-try x0000_revs_x0000_added_x0000_copies e928c65095ed e951f4ad123a : 52031 revs, 9.870343 s, 0.809134 s, -9.061209 s, × 0.0819, 15 µs/rev mozilla-try x00000_revs_x_added_0_copies 6a320851d377 1ebb79acd503 : 363753 revs, 0.094781 s, 47.406785 s, +47.312004 s, × 500.17, 130 µs/rev mozilla-try x00000_revs_x00000_added_0_copies dc8a3ca7010e d16fde900c9c : 444327 revs, 26.690029 s, 0.996219 s, -25.693810 s, × 0.0373, 2 µs/rev mozilla-try x00000_revs_x_added_x_copies 5173c4b6f97c 95d83ee7242d : 362229 revs, 0.094941 s, 47.273399 s, +47.178458 s, × 497.92, 130 µs/rev mozilla-try x00000_revs_x000_added_x_copies 9126823d0e9c ca82787bb23c : 359344 revs, 0.233811 s, 47.419099 s, +47.185288 s, × 202.80, 131 µs/rev mozilla-try x00000_revs_x0000_added_x0000_copies 8d3fafa80d4b eb884023b810 : 192665 revs, 19.321750 s, 3.512653 s, -15.809097 s, × 0.1817, 18 µs/rev mozilla-try x00000_revs_x00000_added_x0000_copies 1b661134e2ca 1ae03d022d6d : 237259 revs, 21.358350 s, 44.459049 s, +23.100699 s, × 2.0815, 187 µs/rev mozilla-try x00000_revs_x00000_added_x000_copies 9b2a99adc05e 8e29777b48e6 : 391148 revs, 25.328737 s, 52.837926 s, +27.509189 s, × 2.0860, 135 µs/rev Differential Revision: https://phab.mercurial-scm.org/D9307

     1

# copies.py - copy detection for Mercurial

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#

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# Copyright 2008 Matt Mackall <mpm@selenic.com>

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#

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# This software may be used and distributed according to the terms of the

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# GNU General Public License version 2 or any later version.

     7

     8

from __future__ import absolute_import

     9

    10

import collections

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import os

    12

    13

from .i18n import _

    14

    15

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from . import (

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    match as matchmod,

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    node,

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    pathutil,

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    policy,

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    pycompat,

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    util,

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)

    24

    25

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from .utils import stringutil

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from .revlogutils import (

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    flagutil,

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    sidedata as sidedatamod,

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)

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rustmod = policy.importrust("copy_tracing")

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    35

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def _filter(src, dst, t):

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    """filters out invalid copies after chaining"""

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    # When _chain()'ing copies in 'a' (from 'src' via some other commit 'mid')

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    # with copies in 'b' (from 'mid' to 'dst'), we can get the different cases

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    # in the following table (not including trivial cases). For example, case 2

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    # is where a file existed in 'src' and remained under that name in 'mid' and

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    # then was renamed between 'mid' and 'dst'.

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    #

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    # case src mid dst result

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    #   1   x   y   -    -

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    #   2   x   y   y   x->y

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    #   3   x   y   x    -

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    #   4   x   y   z   x->z

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    #   5   -   x   y    -

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    #   6   x   x   y   x->y

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    #

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    # _chain() takes care of chaining the copies in 'a' and 'b', but it

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    # cannot tell the difference between cases 1 and 2, between 3 and 4, or

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    # between 5 and 6, so it includes all cases in its result.

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    # Cases 1, 3, and 5 are then removed by _filter().

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    for k, v in list(t.items()):

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        # remove copies from files that didn't exist

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        if v not in src:

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            del t[k]

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        # remove criss-crossed copies

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        elif k in src and v in dst:

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            del t[k]

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        # remove copies to files that were then removed

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        elif k not in dst:

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            del t[k]

    68

    69

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def _chain(prefix, suffix):

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    """chain two sets of copies 'prefix' and 'suffix'"""

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    result = prefix.copy()

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    for key, value in pycompat.iteritems(suffix):

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        result[key] = prefix.get(value, value)

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    return result

    76

    77

    78

def _tracefile(fctx, am, basemf):

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    """return file context that is the ancestor of fctx present in ancestor

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    manifest am

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    Note: we used to try and stop after a given limit, however checking if that

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    limit is reached turned out to be very expensive. we are better off

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    disabling that feature."""

    85

    86

    for f in fctx.ancestors():

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        path = f.path()

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        if am.get(path, None) == f.filenode():

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            return path

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        if basemf and basemf.get(path, None) == f.filenode():

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            return path

    92

    93

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def _dirstatecopies(repo, match=None):

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    ds = repo.dirstate

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    c = ds.copies().copy()

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    for k in list(c):

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        if ds[k] not in b'anm' or (match and not match(k)):

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            del c[k]

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    return c

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def _computeforwardmissing(a, b, match=None):

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    """Computes which files are in b but not a.

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    This is its own function so extensions can easily wrap this call to see what

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    files _forwardcopies is about to process.

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    """

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    ma = a.manifest()

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    mb = b.manifest()

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    return mb.filesnotin(ma, match=match)

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def usechangesetcentricalgo(repo):

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    """Checks if we should use changeset-centric copy algorithms"""

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    if repo.filecopiesmode == b'changeset-sidedata':

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        return True

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    readfrom = repo.ui.config(b'experimental', b'copies.read-from')

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    changesetsource = (b'changeset-only', b'compatibility')

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    return readfrom in changesetsource

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   121

   122

def _committedforwardcopies(a, b, base, match):

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    """Like _forwardcopies(), but b.rev() cannot be None (working copy)"""

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    # files might have to be traced back to the fctx parent of the last

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    # one-side-only changeset, but not further back than that

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    repo = a._repo

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   128

    if usechangesetcentricalgo(repo):

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        return _changesetforwardcopies(a, b, match)

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    debug = repo.ui.debugflag and repo.ui.configbool(b'devel', b'debug.copies')

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    dbg = repo.ui.debug

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    if debug:

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        dbg(b'debug.copies:    looking into rename from %s to %s\n' % (a, b))

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    am = a.manifest()

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    basemf = None if base is None else base.manifest()

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    # find where new files came from

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    # we currently don't try to find where old files went, too expensive

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    # this means we can miss a case like 'hg rm b; hg cp a b'

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    cm = {}

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    # Computing the forward missing is quite expensive on large manifests, since

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    # it compares the entire manifests. We can optimize it in the common use

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    # case of computing what copies are in a commit versus its parent (like

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    # during a rebase or histedit). Note, we exclude merge commits from this

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    # optimization, since the ctx.files() for a merge commit is not correct for

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    # this comparison.

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    forwardmissingmatch = match

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    if b.p1() == a and b.p2().node() == node.nullid:

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        filesmatcher = matchmod.exact(b.files())

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        forwardmissingmatch = matchmod.intersectmatchers(match, filesmatcher)

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    missing = _computeforwardmissing(a, b, match=forwardmissingmatch)

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    ancestrycontext = a._repo.changelog.ancestors([b.rev()], inclusive=True)

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   157

    if debug:

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        dbg(b'debug.copies:      missing files to search: %d\n' % len(missing))

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    for f in sorted(missing):

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        if debug:

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            dbg(b'debug.copies:        tracing file: %s\n' % f)

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        fctx = b[f]

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        fctx._ancestrycontext = ancestrycontext

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        if debug:

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            start = util.timer()

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        opath = _tracefile(fctx, am, basemf)

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        if opath:

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            if debug:

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                dbg(b'debug.copies:          rename of: %s\n' % opath)

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            cm[f] = opath

   173

        if debug:

   174

            dbg(

   175

                b'debug.copies:          time: %f seconds\n'

   176

                % (util.timer() - start)

   177

            )

   178

    return cm

   179

   180

   181

def _revinfo_getter(repo, match):

   182

    """returns a function that returns the following data given a <rev>"

   183

   184

    * p1: revision number of first parent

   185

    * p2: revision number of first parent

   186

    * changes: a ChangingFiles object

   187

    """

   188

    cl = repo.changelog

   189

    parents = cl.parentrevs

   190

    flags = cl.flags

   191

   192

    HASCOPIESINFO = flagutil.REVIDX_HASCOPIESINFO

   193

   194

    changelogrevision = cl.changelogrevision

   195

   196

    # A small cache to avoid doing the work twice for merges

   197

    #

   198

    # In the vast majority of cases, if we ask information for a revision

   199

    # about 1 parent, we'll later ask it for the other. So it make sense to

   200

    # keep the information around when reaching the first parent of a merge

   201

    # and dropping it after it was provided for the second parents.

   202

    #

   203

    # It exists cases were only one parent of the merge will be walked. It

   204

    # happens when the "destination" the copy tracing is descendant from a

   205

    # new root, not common with the "source". In that case, we will only walk

   206

    # through merge parents that are descendant of changesets common

   207

    # between "source" and "destination".

   208

    #

   209

    # With the current case implementation if such changesets have a copy

   210

    # information, we'll keep them in memory until the end of

   211

    # _changesetforwardcopies. We don't expect the case to be frequent

   212

    # enough to matters.

   213

    #

   214

    # In addition, it would be possible to reach pathological case, were

   215

    # many first parent are met before any second parent is reached. In

   216

    # that case the cache could grow. If this even become an issue one can

   217

    # safely introduce a maximum cache size. This would trade extra CPU/IO

   218

    # time to save memory.

   219

    merge_caches = {}

   220

   221

    alwaysmatch = match.always()

   222

   223

    if rustmod is not None and alwaysmatch:

   224

   225

        def revinfo(rev):

   226

            p1, p2 = parents(rev)

   227

            value = None

   228

            e = merge_caches.pop(rev, None)

   229

            if e is not None:

   230

                return e

   231

            if flags(rev) & HASCOPIESINFO:

   232

                raw = changelogrevision(rev)._sidedata.get(sidedatamod.SD_FILES)

   233

            else:

   234

                raw = None

   235

            value = (p1, p2, raw)

   236

            if p1 != node.nullrev and p2 != node.nullrev:

   237

                # XXX some case we over cache, IGNORE

   238

                merge_caches[rev] = value

   239

            return value

   240

   241

    else:

   242

   243

        def revinfo(rev):

   244

            p1, p2 = parents(rev)

   245

            value = None

   246

            e = merge_caches.pop(rev, None)

   247

            if e is not None:

   248

                return e

   249

            changes = None

   250

            if flags(rev) & HASCOPIESINFO:

   251

                changes = changelogrevision(rev).changes

   252

            value = (p1, p2, changes)

   253

            if p1 != node.nullrev and p2 != node.nullrev:

   254

                # XXX some case we over cache, IGNORE

   255

                merge_caches[rev] = value

   256

            return value

   257

   258

    return revinfo

   259

   260

   261

def cached_is_ancestor(is_ancestor):

   262

    """return a cached version of is_ancestor"""

   263

    cache = {}

   264

   265

    def _is_ancestor(anc, desc):

   266

        if anc > desc:

   267

            return False

   268

        elif anc == desc:

   269

            return True

   270

        key = (anc, desc)

   271

        ret = cache.get(key)

   272

        if ret is None:

   273

            ret = cache[key] = is_ancestor(anc, desc)

   274

        return ret

   275

   276

    return _is_ancestor

   277

   278

   279

def _changesetforwardcopies(a, b, match):

   280

    if a.rev() in (node.nullrev, b.rev()):

   281

        return {}

   282

   283

    repo = a.repo().unfiltered()

   284

    children = {}

   285

   286

    cl = repo.changelog

   287

    isancestor = cl.isancestorrev

   288

    missingrevs = cl.findmissingrevs(common=[a.rev()], heads=[b.rev()])

   289

    mrset = set(missingrevs)

   290

    roots = set()

   291

    for r in missingrevs:

   292

        for p in cl.parentrevs(r):

   293

            if p == node.nullrev:

   294

                continue

   295

            if p not in children:

   296

                children[p] = [r]

   297

            else:

   298

                children[p].append(r)

   299

            if p not in mrset:

   300

                roots.add(p)

   301

    if not roots:

   302

        # no common revision to track copies from

   303

        return {}

   304

    min_root = min(roots)

   305

   306

    from_head = set(

   307

        cl.reachableroots(min_root, [b.rev()], list(roots), includepath=True)

   308

    )

   309

   310

    iterrevs = set(from_head)

   311

    iterrevs &= mrset

   312

    iterrevs.update(roots)

   313

    iterrevs.remove(b.rev())

   314

    revs = sorted(iterrevs)

   315

   316

    if repo.filecopiesmode == b'changeset-sidedata':

   317

        revinfo = _revinfo_getter(repo, match)

   318

        return _combine_changeset_copies(

   319

            revs, children, b.rev(), revinfo, match, isancestor

   320

        )

   321

    else:

   322

        revinfo = _revinfo_getter_extra(repo)

   323

        return _combine_changeset_copies_extra(

   324

            revs, children, b.rev(), revinfo, match, isancestor

   325

        )

   326

   327

   328

def _combine_changeset_copies(

   329

    revs, children, targetrev, revinfo, match, isancestor

   330

):

   331

    """combine the copies information for each item of iterrevs

   332

   333

    revs: sorted iterable of revision to visit

   334

    children: a {parent: [children]} mapping.

   335

    targetrev: the final copies destination revision (not in iterrevs)

   336

    revinfo(rev): a function that return (p1, p2, p1copies, p2copies, removed)

   337

    match: a matcher

   338

   339

    It returns the aggregated copies information for `targetrev`.

   340

    """

   341

   342

    alwaysmatch = match.always()

   343

   344

    if rustmod is not None and alwaysmatch:

   345

        return rustmod.combine_changeset_copies(

   346

            list(revs), children, targetrev, revinfo, isancestor

   347

        )

   348

   349

    isancestor = cached_is_ancestor(isancestor)

   350

   351

    all_copies = {}

   352

    for r in revs:

   353

        copies = all_copies.pop(r, None)

   354

        if copies is None:

   355

            # this is a root

   356

            copies = {}

   357

        for i, c in enumerate(children[r]):

   358

            p1, p2, changes = revinfo(c)

   359

            childcopies = {}

   360

            if r == p1:

   361

                parent = 1

   362

                if changes is not None:

   363

                    childcopies = changes.copied_from_p1

   364

            else:

   365

                assert r == p2

   366

                parent = 2

   367

                if changes is not None:

   368

                    childcopies = changes.copied_from_p2

   369

            if not alwaysmatch:

   370

                childcopies = {

   371

                    dst: src for dst, src in childcopies.items() if match(dst)

   372

                }

   373

            newcopies = copies

   374

            if childcopies:

   375

                newcopies = copies.copy()

   376

                for dest, source in pycompat.iteritems(childcopies):

   377

                    prev = copies.get(source)

   378

                    if prev is not None and prev[1] is not None:

   379

                        source = prev[1]

   380

                    newcopies[dest] = (c, source)

   381

                assert newcopies is not copies

   382

            if changes is not None and changes.removed:

   383

                if newcopies is copies:

   384

                    newcopies = copies.copy()

   385

                for f in changes.removed:

   386

                    if f in newcopies:

   387

                        if newcopies is copies:

   388

                            # copy on write to avoid affecting potential other

   389

                            # branches.  when there are no other branches, this

   390

                            # could be avoided.