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https://github.com/facebook/sapling.git
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65d9160c6f
Summary: Vendor git's xdiff library from git commit d7c6c2369d7c6c2369ac21141b7c6cceaebc6414ec3da14ad using GPL2+ license. There is another recent user report that hg diff generates suboptimal result. It seems the fix to issue4074 isn't good enough. I crafted some other interesting cases, and hg diff barely has any advantage compared with gnu diffutils or git diff. | testcase | gnu diffutils | hg diff | git diff | | | lines time | lines time | lines time | | patience | 6 0.00 | 602 0.08 | 6 0.00 | | random | 91772 0.90 | 109462 0.70 | 91772 0.24 | | json | 2 0.03 | 1264814 1.81 | 2 0.29 | "lines" means the size of the output, i.e. the count of "+/-" lines. "time" means seconds needed to do the calculation. Both are the smaller the better. "hg diff" counts Python startup overhead. Git and GNU diffutils generate optimal results. For the "json" case, git can have an optimization that does a scan for common prefix and suffix first, and match them if the length is greater than half of the text. See https://neil.fraser.name/news/2006/03/12/. That would make git the fastest for all above cases. About testcases: patience: Aiming for the weakness of the greedy "patience diff" algorithm. Using git's patience diff option would also get suboptimal result. Generated using the Python script: ``` open('a', 'w').write('\n'.join(list('a' + 'x' * 300 + 'u' + 'x' * 700 + 'a\n'))) open('b', 'w').write('\n'.join(list('b' + 'x' * 700 + 'u' + 'x' * 300 + 'b\n'))) ``` random: Generated using the script in `test-issue4074.t`. It practically makes the algorithm suffer. Impressively, git wins in both performance and diff quality. json: The recent user reported case. It's a single line movement near the end of a very large (800K lines) JSON file. Reviewed By: ryanmce Differential Revision: D7124455 fbshipit-source-id: 832651115da770f9d2ed5fdff2e200453c0013f8
35 lines
1.0 KiB
C
35 lines
1.0 KiB
C
/*
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* LibXDiff by Davide Libenzi ( File Differential Library )
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* Copyright (C) 2003 Davide Libenzi
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, see
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* <http://www.gnu.org/licenses/>.
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*
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* Davide Libenzi <davidel@xmailserver.org>
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*
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*/
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#if !defined(XPREPARE_H)
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#define XPREPARE_H
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int xdl_prepare_env(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
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xdfenv_t *xe);
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void xdl_free_env(xdfenv_t *xe);
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#endif /* #if !defined(XPREPARE_H) */
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