From patchwork Mon Nov 20 19:18:52 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Antonin Delpeuch X-Patchwork-Id: 13461941 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="CHSuYHHo" Received: from mail-lj1-x22c.google.com (mail-lj1-x22c.google.com [IPv6:2a00:1450:4864:20::22c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7C2AB13D for ; Mon, 20 Nov 2023 11:19:23 -0800 (PST) Received: by mail-lj1-x22c.google.com with SMTP id 38308e7fff4ca-2c523ac38fbso60529771fa.0 for ; Mon, 20 Nov 2023 11:19:23 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1700507961; x=1701112761; darn=vger.kernel.org; h=cc:to:mime-version:content-transfer-encoding:fcc:subject:date:from :references:in-reply-to:message-id:from:to:cc:subject:date :message-id:reply-to; bh=JmlFnBj0HFsqk0XzN1cFxZadVdwnIh5ZdkyvwEBFrCs=; b=CHSuYHHonnXkbAE6hKElnx19/K4X0nvmO451KwTUd5wm0CC1rrvaH52Sv5GYRbuQdz Ng2ocfETqk6v2fYLhjxiFh2mt5fVZk/2TBGLVj6FEwAJDi+TFPPVRwIpYRYej5EGaeCr Xdbqyyca33JcCufBBYEFhpXf+id2O8J84RuRzh2w7RxwHEDnCacV4UqjSiOc2POzZuxP 0qfdiFuUQPIc3n/PzOAEnLB++UDRG51Hea1EKGOpXMjPKPqGDzQxe5/B0pppdtI1ANt2 idLNFf+eWTXgnCDjIKJ9QqvvFw4tWAAl2XUXhE68WQmvBzPfxEsA2jVnmBdqNASvbkWX Zv/Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1700507961; x=1701112761; h=cc:to:mime-version:content-transfer-encoding:fcc:subject:date:from :references:in-reply-to:message-id:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=JmlFnBj0HFsqk0XzN1cFxZadVdwnIh5ZdkyvwEBFrCs=; b=PkW69JvhK93af+NvOd9KP43Vnet/7kZ23DwPnL8Atdd2hemFX+P3q4L5eDr8Z/4XEf alBFA5mwYTQSNhbdgmdD9szmRfq9uSOqdac8v9LmQyWl06nb9/I6Ud/602qeYPW7Sqhf undm6JlFH/IHAgfUb7r5d2juJ8MMyu1BiyftIDMe6kF9w7JzNcIOxa00z9/FBFWnG/5/ KHUlDX8lhI/djzaQRrToH/pIfLmD9Lk8IasFDAGzxb4rk1iWOb30deHIVMyQkq3rsGVQ 2fSDgH09+LsMFpXoI8pLDyF87D3a1XBEyhO1fKQDeIGAuHIKaB+46259r8/6otxKJyDX Zffw== X-Gm-Message-State: AOJu0Yy1e0AKQfM+oiqfoEgNn7ehrM1IfZJISFRbhouoryvumXJ61V2t c7di7HGhSSuJUX/qJNhfJs+0ILIkDZI= X-Google-Smtp-Source: AGHT+IGWNb6P0xYnRdh1tQ4DNjcyWZ4kxsAYCzGKWZ5C/h8yczO3NV7VZ5MqEMWX3dLgDpQRw9+gEQ== X-Received: by 2002:a2e:9157:0:b0:2c0:7d6:570a with SMTP id q23-20020a2e9157000000b002c007d6570amr5682790ljg.33.1700507960359; Mon, 20 Nov 2023 11:19:20 -0800 (PST) Received: from [127.0.0.1] ([13.74.141.28]) by smtp.gmail.com with ESMTPSA id j3-20020a056000124300b0032f7e832cabsm11993367wrx.90.2023.11.20.11.18.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Nov 2023 11:19:05 -0800 (PST) Message-ID: In-Reply-To: References: Date: Mon, 20 Nov 2023 19:18:52 +0000 Subject: [PATCH v2] merge-file: add --diff-algorithm option Fcc: Sent Precedence: bulk X-Mailing-List: git@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 To: git@vger.kernel.org Cc: Phillip Wood , Antonin Delpeuch , Antonin Delpeuch From: Antonin Delpeuch From: Antonin Delpeuch This makes it possible to use other diff algorithms than the 'myers' default algorithm, when using the 'git merge-file' command. This helps avoid spurious conflicts by selecting a more recent algorithm such as 'histogram', for instance when using 'git merge-file' as part of a custom merge driver. Signed-off-by: Antonin Delpeuch Reviewed-by: Phillip Wood --- merge-file: add --diff-algorithm option Changes since v1: * improve commit message to mention the use case of custom merge drivers * improve documentation to show available options and recommend switching to "histogram" * add tests I have left out: * switching the default to "histogram", because it should only be done in a subsequent release * adding a configuration variable to control this option, because I was not sure how to call it. Perhaps "merge-file.diffAlgorithm"? Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1606%2Fwetneb%2Fmerge_file_configurable_diff_algorithm-v2 Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1606/wetneb/merge_file_configurable_diff_algorithm-v2 Pull-Request: https://github.com/git/git/pull/1606 Range-diff vs v1: 1: 4aa453e30be ! 1: 842b5abf33c merge-file: add --diff-algorithm option @@ Commit message merge-file: add --diff-algorithm option This makes it possible to use other diff algorithms than the 'myers' - default algorithm, when using the 'git merge-file' command. + default algorithm, when using the 'git merge-file' command. This helps + avoid spurious conflicts by selecting a more recent algorithm such as + 'histogram', for instance when using 'git merge-file' as part of a custom + merge driver. Signed-off-by: Antonin Delpeuch + Reviewed-by: Phillip Wood ## Documentation/git-merge-file.txt ## @@ Documentation/git-merge-file.txt: object store and the object ID of its blob is written to standard output. Instead of leaving conflicts in the file, resolve conflicts favouring our (or their or both) side of the lines. -+--diff-algorithm :: -+ Use a different diff algorithm while merging, which can help ++--diff-algorithm={patience|minimal|histogram|myers}:: ++ Use a different diff algorithm while merging. The current default is "myers", ++ but selecting more recent algorithm such as "histogram" can help + avoid mismerges that occur due to unimportant matching lines -+ (such as braces from distinct functions). See also ++ (such as braces from distinct functions). See also + linkgit:git-diff[1] `--diff-algorithm`. EXAMPLES @@ builtin/merge-file.c: int cmd_merge_file(int argc, const char **argv, const char OPT_INTEGER(0, "marker-size", &xmp.marker_size, N_("for conflicts, use this marker size")), OPT__QUIET(&quiet, N_("do not warn about conflicts")), + + ## t/t6403-merge-file.sh ## +@@ t/t6403-merge-file.sh: test_expect_success 'setup' ' + deduxit me super semitas jusitiae, + EOF + +- printf "propter nomen suum." >>new4.txt ++ printf "propter nomen suum." >>new4.txt && ++ ++ cat >base.c <<-\EOF && ++ int f(int x, int y) ++ { ++ if (x == 0) ++ { ++ return y; ++ } ++ return x; ++ } ++ ++ int g(size_t u) ++ { ++ while (u < 30) ++ { ++ u++; ++ } ++ return u; ++ } ++ EOF ++ ++ cat >ours.c <<-\EOF && ++ int g(size_t u) ++ { ++ while (u < 30) ++ { ++ u++; ++ } ++ return u; ++ } ++ ++ int h(int x, int y, int z) ++ { ++ if (z == 0) ++ { ++ return x; ++ } ++ return y; ++ } ++ EOF ++ ++ cat >theirs.c <<-\EOF ++ int f(int x, int y) ++ { ++ if (x == 0) ++ { ++ return y; ++ } ++ return x; ++ } ++ ++ int g(size_t u) ++ { ++ while (u > 34) ++ { ++ u--; ++ } ++ return u; ++ } ++ EOF + ' + + test_expect_success 'merge with no changes' ' +@@ t/t6403-merge-file.sh: test_expect_success '--object-id fails without repository' ' + grep "not a git repository" err + ' + ++test_expect_success 'merging C files with "myers" diff algorithm creates some spurious conflicts' ' ++ cat >expect.c <<-\EOF && ++ int g(size_t u) ++ { ++ while (u < 30) ++ { ++ u++; ++ } ++ return u; ++ } ++ ++ int h(int x, int y, int z) ++ { ++ <<<<<<< ours.c ++ if (z == 0) ++ ||||||| base.c ++ while (u < 30) ++ ======= ++ while (u > 34) ++ >>>>>>> theirs.c ++ { ++ <<<<<<< ours.c ++ return x; ++ ||||||| base.c ++ u++; ++ ======= ++ u--; ++ >>>>>>> theirs.c ++ } ++ return y; ++ } ++ EOF ++ ++ test_must_fail git merge-file -p --diff3 --diff-algorithm myers ours.c base.c theirs.c >myers_output.c && ++ test_cmp expect.c myers_output.c ++' ++ ++test_expect_success 'merging C files with "histogram" diff algorithm avoids some spurious conflicts' ' ++ cat >expect.c <<-\EOF && ++ int g(size_t u) ++ { ++ while (u > 34) ++ { ++ u--; ++ } ++ return u; ++ } ++ ++ int h(int x, int y, int z) ++ { ++ if (z == 0) ++ { ++ return x; ++ } ++ return y; ++ } ++ EOF ++ ++ git merge-file -p --diff3 --diff-algorithm histogram ours.c base.c theirs.c >histogram_output.c && ++ test_cmp expect.c histogram_output.c ++' ++ + test_done Documentation/git-merge-file.txt | 6 ++ builtin/merge-file.c | 28 +++++++ t/t6403-merge-file.sh | 124 ++++++++++++++++++++++++++++++- 3 files changed, 157 insertions(+), 1 deletion(-) base-commit: 98009afd24e2304bf923a64750340423473809ff diff --git a/Documentation/git-merge-file.txt b/Documentation/git-merge-file.txt index 6a081eacb72..71915a00fa4 100644 --- a/Documentation/git-merge-file.txt +++ b/Documentation/git-merge-file.txt @@ -92,6 +92,12 @@ object store and the object ID of its blob is written to standard output. Instead of leaving conflicts in the file, resolve conflicts favouring our (or their or both) side of the lines. +--diff-algorithm={patience|minimal|histogram|myers}:: + Use a different diff algorithm while merging. The current default is "myers", + but selecting more recent algorithm such as "histogram" can help + avoid mismerges that occur due to unimportant matching lines + (such as braces from distinct functions). See also + linkgit:git-diff[1] `--diff-algorithm`. EXAMPLES -------- diff --git a/builtin/merge-file.c b/builtin/merge-file.c index 832c93d8d54..1f987334a31 100644 --- a/builtin/merge-file.c +++ b/builtin/merge-file.c @@ -1,5 +1,6 @@ #include "builtin.h" #include "abspath.h" +#include "diff.h" #include "hex.h" #include "object-name.h" #include "object-store.h" @@ -28,6 +29,30 @@ static int label_cb(const struct option *opt, const char *arg, int unset) return 0; } +static int set_diff_algorithm(xpparam_t *xpp, + const char *alg) +{ + long diff_algorithm = parse_algorithm_value(alg); + if (diff_algorithm < 0) + return -1; + xpp->flags = (xpp->flags & ~XDF_DIFF_ALGORITHM_MASK) | diff_algorithm; + return 0; +} + +static int diff_algorithm_cb(const struct option *opt, + const char *arg, int unset) +{ + xpparam_t *xpp = opt->value; + + BUG_ON_OPT_NEG(unset); + + if (set_diff_algorithm(xpp, arg)) + return error(_("option diff-algorithm accepts \"myers\", " + "\"minimal\", \"patience\" and \"histogram\"")); + + return 0; +} + int cmd_merge_file(int argc, const char **argv, const char *prefix) { const char *names[3] = { 0 }; @@ -48,6 +73,9 @@ int cmd_merge_file(int argc, const char **argv, const char *prefix) XDL_MERGE_FAVOR_THEIRS), OPT_SET_INT(0, "union", &xmp.favor, N_("for conflicts, use a union version"), XDL_MERGE_FAVOR_UNION), + OPT_CALLBACK_F(0, "diff-algorithm", &xmp.xpp, N_(""), + N_("choose a diff algorithm"), + PARSE_OPT_NONEG, diff_algorithm_cb), OPT_INTEGER(0, "marker-size", &xmp.marker_size, N_("for conflicts, use this marker size")), OPT__QUIET(&quiet, N_("do not warn about conflicts")), diff --git a/t/t6403-merge-file.sh b/t/t6403-merge-file.sh index 2c92209ecab..fb872c5a113 100755 --- a/t/t6403-merge-file.sh +++ b/t/t6403-merge-file.sh @@ -56,7 +56,67 @@ test_expect_success 'setup' ' deduxit me super semitas jusitiae, EOF - printf "propter nomen suum." >>new4.txt + printf "propter nomen suum." >>new4.txt && + + cat >base.c <<-\EOF && + int f(int x, int y) + { + if (x == 0) + { + return y; + } + return x; + } + + int g(size_t u) + { + while (u < 30) + { + u++; + } + return u; + } + EOF + + cat >ours.c <<-\EOF && + int g(size_t u) + { + while (u < 30) + { + u++; + } + return u; + } + + int h(int x, int y, int z) + { + if (z == 0) + { + return x; + } + return y; + } + EOF + + cat >theirs.c <<-\EOF + int f(int x, int y) + { + if (x == 0) + { + return y; + } + return x; + } + + int g(size_t u) + { + while (u > 34) + { + u--; + } + return u; + } + EOF ' test_expect_success 'merge with no changes' ' @@ -447,4 +507,66 @@ test_expect_success '--object-id fails without repository' ' grep "not a git repository" err ' +test_expect_success 'merging C files with "myers" diff algorithm creates some spurious conflicts' ' + cat >expect.c <<-\EOF && + int g(size_t u) + { + while (u < 30) + { + u++; + } + return u; + } + + int h(int x, int y, int z) + { + <<<<<<< ours.c + if (z == 0) + ||||||| base.c + while (u < 30) + ======= + while (u > 34) + >>>>>>> theirs.c + { + <<<<<<< ours.c + return x; + ||||||| base.c + u++; + ======= + u--; + >>>>>>> theirs.c + } + return y; + } + EOF + + test_must_fail git merge-file -p --diff3 --diff-algorithm myers ours.c base.c theirs.c >myers_output.c && + test_cmp expect.c myers_output.c +' + +test_expect_success 'merging C files with "histogram" diff algorithm avoids some spurious conflicts' ' + cat >expect.c <<-\EOF && + int g(size_t u) + { + while (u > 34) + { + u--; + } + return u; + } + + int h(int x, int y, int z) + { + if (z == 0) + { + return x; + } + return y; + } + EOF + + git merge-file -p --diff3 --diff-algorithm histogram ours.c base.c theirs.c >histogram_output.c && + test_cmp expect.c histogram_output.c +' + test_done