Re: [PATCH v2] merge-tree: add -X strategy option

From: Elijah Newren <newren@gmail.com>
Date: Sep 12, 2023, 15:03 UTC
Message-ID: <CABPp-BG+MxZukNagJD90GgTOh1Te8Dk3pk86DOhSpxasAJViFQ@mail.gmail.com>
In-Reply-To: <pull.1565.v2.git.1691818386345.gitgitgadget@gmail.com>

Hi,

Sorry for the delay in responding; I've been busy with non-git things...

On Sat, Aug 12, 2023 at 12:19 AM Izzy via GitGitGadget <gitgitgadget@gmail.com> wrote:

Show 7 quoted lines

>
> From: winglovet <winglovet@gmail.com>
>
> Add merge strategy option to produce more customizable merge result such
> as automatically solve conflicts.
>
> Signed-off-by: winglovet <winglovet@gmail.com>

Junio already flagged this line in your v1; you either need to correct it or respond to his comments about it.

Show 78 quoted lines

> ---
>     merge-tree: add -X strategy option
>
>     Change-Id: I16be592262d13cebcff8726eb043f7ecdb313b76
>
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1565%2FWingT%2Fmerge_tree_allow_strategy_option-v2
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1565/WingT/merge_tree_allow_strategy_option-v2
> Pull-Request: https://github.com/gitgitgadget/git/pull/1565
>
> Range-diff vs v1:
>
>  1:  b843caed596 ! 1:  7d53d08381e merge-tree: add -X strategy option
>      @@ builtin/merge-tree.c: int cmd_merge_tree(int argc, const char **argv, const char
>         /* Handle --stdin */
>         if (o.use_stdin) {
>                 struct strbuf buf = STRBUF_INIT;
>      +
>      + ## t/t4301-merge-tree-write-tree.sh ##
>      +@@ t/t4301-merge-tree-write-tree.sh: test_expect_success setup '
>      +  git branch side1 &&
>      +  git branch side2 &&
>      +  git branch side3 &&
>      ++ git branch side4 &&
>      +
>      +  git checkout side1 &&
>      +  test_write_lines 1 2 3 4 5 6 >numbers &&
>      +@@ t/t4301-merge-tree-write-tree.sh: test_expect_success setup '
>      +  test_tick &&
>      +  git commit -m rename-numbers &&
>      +
>      ++ git checkout side4 &&
>      ++ test_write_lines 0 1 2 3 4 5 >numbers &&
>      ++ echo yo >greeting &&
>      ++ git add numbers greeting &&
>      ++ test_tick &&
>      ++ git commit -m other-content-modifications &&
>      ++
>      +  git switch --orphan unrelated &&
>      +  >something-else &&
>      +  git add something-else &&
>      +@@ t/t4301-merge-tree-write-tree.sh: test_expect_success 'Content merge and a few conflicts' '
>      +  test_cmp expect actual
>      + '
>      +
>      ++test_expect_success 'Auto resolve conflicts by "ours" stragety option' '
>      ++ git checkout side1^0 &&
>      ++
>      ++ # make sure merge conflict exists
>      ++ test_must_fail git merge side4 &&
>      ++ git merge --abort &&
>      ++
>      ++ git merge -X ours side4 &&
>      ++ git rev-parse HEAD^{tree} > expected &&
>      ++
>      ++    git merge-tree -X ours side1 side4 > actual &&
>      ++
>      ++ test_cmp expected actual
>      ++'
>      ++
>      + test_expect_success 'Barf on misspelled option, with exit code other than 0 or 1' '
>      +  # Mis-spell with single "s" instead of double "s"
>      +  test_expect_code 129 git merge-tree --write-tree --mesages FOOBAR side1 side2 2>expect &&
>
>
>  builtin/merge-tree.c             | 24 ++++++++++++++++++++++++
>  t/t4301-merge-tree-write-tree.sh | 23 +++++++++++++++++++++++
>  2 files changed, 47 insertions(+)
>
> diff --git a/builtin/merge-tree.c b/builtin/merge-tree.c
> index 0de42aecf4b..2ec6ec0d39a 100644
> --- a/builtin/merge-tree.c
> +++ b/builtin/merge-tree.c
> @@ -19,6 +19,8 @@
>  #include "tree.h"
>  #include "config.h"
>
> +static const char **xopts;
> +static size_t xopts_nr, xopts_alloc;

I know we already have lots of globals, and I'm partially to blame since I also copied this style from elsewhere into this file, but it'd sure be nice to get rid of these needless globals rather than add more. But, certainly not a blocker....

Show 9 quoted lines

>  static int line_termination = '\n';
>
>  struct merge_list {
> @@ -414,6 +416,7 @@ struct merge_tree_options {
>         int show_messages;
>         int name_only;
>         int use_stdin;
> +       struct merge_options merge_options;
>  };

Probably the best we can do now, but feels a little icky to me that parse_merge_opt() works on all of struct merge_options rather than having a dedicated struct for the particular options it can set. Made sense back in the merge-recursive.[ch] days, but it provides too many extra unrelated and unnecessary fields now.

This isn't something you need to fix in this patch, though, just something else I'll keep in mind when I get back to working on removing merge-recursive.[ch].

Show 81 quoted lines

>  static int real_merge(struct merge_tree_options *o,
> @@ -439,6 +442,8 @@ static int real_merge(struct merge_tree_options *o,
>
>         init_merge_options(&opt, the_repository);
>
> +       opt.recursive_variant = o->merge_options.recursive_variant;
> +
>         opt.show_rename_progress = 0;
>
>         opt.branch1 = branch1;
> @@ -510,6 +515,17 @@ static int real_merge(struct merge_tree_options *o,
>         return !result.clean; /* result.clean < 0 handled above */
>  }
>
> +static int option_parse_x(const struct option *opt,
> +                         const char *arg, int unset)
> +{
> +       if (unset)
> +               return 0;
> +
> +       ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
> +       xopts[xopts_nr++] = xstrdup(arg);
> +       return 0;
> +}
> +
>  int cmd_merge_tree(int argc, const char **argv, const char *prefix)
>  {
>         struct merge_tree_options o = { .show_messages = -1 };
> @@ -548,6 +564,10 @@ int cmd_merge_tree(int argc, const char **argv, const char *prefix)
>                            &merge_base,
>                            N_("commit"),
>                            N_("specify a merge-base for the merge")),
> +               OPT_CALLBACK('X', "strategy-option", &xopts,
> +                       N_("option=value"),
> +                       N_("option for selected merge strategy"),
> +                       option_parse_x),
>                 OPT_END()
>         };
>
> @@ -556,6 +576,10 @@ int cmd_merge_tree(int argc, const char **argv, const char *prefix)
>         argc = parse_options(argc, argv, prefix, mt_options,
>                              merge_tree_usage, PARSE_OPT_STOP_AT_NON_OPTION);
>
> +       for (int x = 0; x < xopts_nr; x++)
> +               if (parse_merge_opt(&o.merge_options, xopts[x]))
> +                       die(_("unknown strategy option: -X%s"), xopts[x]);
> +
>         /* Handle --stdin */
>         if (o.use_stdin) {
>                 struct strbuf buf = STRBUF_INIT;
> diff --git a/t/t4301-merge-tree-write-tree.sh b/t/t4301-merge-tree-write-tree.sh
> index 250f721795b..2718817628c 100755
> --- a/t/t4301-merge-tree-write-tree.sh
> +++ b/t/t4301-merge-tree-write-tree.sh
> @@ -22,6 +22,7 @@ test_expect_success setup '
>         git branch side1 &&
>         git branch side2 &&
>         git branch side3 &&
> +       git branch side4 &&
>
>         git checkout side1 &&
>         test_write_lines 1 2 3 4 5 6 >numbers &&
> @@ -46,6 +47,13 @@ test_expect_success setup '
>         test_tick &&
>         git commit -m rename-numbers &&
>
> +       git checkout side4 &&
> +       test_write_lines 0 1 2 3 4 5 >numbers &&
> +       echo yo >greeting &&
> +       git add numbers greeting &&
> +       test_tick &&
> +       git commit -m other-content-modifications &&
> +
>         git switch --orphan unrelated &&
>         >something-else &&
>         git add something-else &&
> @@ -97,6 +105,21 @@ test_expect_success 'Content merge and a few conflicts' '
>         test_cmp expect actual
>  '
>
> +test_expect_success 'Auto resolve conflicts by "ours" stragety option' '

stragety -> strategy

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> +       git checkout side1^0 &&
> +
> +       # make sure merge conflict exists
> +       test_must_fail git merge side4 &&
> +       git merge --abort &&
> +
> +       git merge -X ours side4 &&
> +       git rev-parse HEAD^{tree} > expected &&

Style: '>filename', not '> filename'.

> +
> +    git merge-tree -X ours side1 side4 > actual &&

Same style issue with redirect.

Also, why is the leading spacing inconsistent with the surrounding lines?

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> +
> +       test_cmp expected actual
> +'
> +
>  test_expect_success 'Barf on misspelled option, with exit code other than 0 or 1' '
>         # Mis-spell with single "s" instead of double "s"
>         test_expect_code 129 git merge-tree --write-tree --mesages FOOBAR side1 side2 2>expect &&

I personally don't see the value in passing `-X ours` or `-X theirs` to merges. I've never really been a fan of either. Granted, I understand the value in making merge-tree support the same things that existing merges support, so I'm fine with supporting it, but I'd rather have a useful example for the testcase such as -Xignore-space-change or something (or maybe use it as an additional example?) Not a blocker on its own, but just a personal preference.

Anyway, the general direction of the patch seems reasonable. Not everything I commented on needs to be fixed, as I noted, but there are a few small things to fix up.