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Re: [PATCH v4 3/3] rebase: add a config option for --rebase-merges

From
Johannes Schindelin <johannes.schindelin@gmx.de>
Date
Feb 24, 2023, 13:53 UTC
Message-ID
<c918797c-75cc-80d4-c978-360388877d63@gmx.de>
In-Reply-To
<20230223053410.644503-3-alexhenrie24@gmail.com>
Hi Alex,
On Wed, 22 Feb 2023, Alex Henrie wrote:
Show 12 quoted lines
> diff --git a/builtin/rebase.c b/builtin/rebase.c
> index b68fc2fbb7..45cf445d42 100644
> --- a/builtin/rebase.c
> +++ b/builtin/rebase.c
> @@ -771,6 +771,20 @@ static int run_specific_rebase(struct rebase_options *opts)
>  	return status ? -1 : 0;
>  }
>
> +static void parse_merges_value(struct rebase_options *options, const char *value)
> +{
> +	if (value) {
> +		if (!strcmp("no-rebase-cousins", value))

If you want to support `rebase.merges=` to imply `no-rebase-cousins`, this would be the correct place to do it:

		if (!*value || !strcmp("no-rebase-cousins", value))
Show 8 quoted lines
> +			options->rebase_cousins = 0;
> +		else if (!strcmp("rebase-cousins", value))
> +			options->rebase_cousins = 1;
> +		else
> +			die(_("Unknown mode: %s"), value);
> +	}
> +
> +	options->rebase_merges = 1;

I would expect `options->rebase_merges = 0` if `value == NULL`. IOW I would have expected `parse_merges_value()` to start with:

	if (!value) {
		options->rebase_merges = 0;
		return;
	}

This assumes, of course, the parse_options semantics, where a `--no-*` option passes `NULL` as argument to the callback.

However, this is _not_ the parse_options callback, and if the (optional) argument was not specified, we do end up with a `NULL` here in spite of wanting to enable the rebase-merges mode.

However, a primary reason why you introduce the function is to support config value parsing. And in config value parsing, a "maybe-bool" with a NULL value is considered to be equivalent to `true`! (See `git_parse_maybe_bool_text()` or https://git-scm.com/docs/git-config#Documentation/git-config.txt-true for details.). For example,

	[http]
		sslVerify
is equivalent to
	[http]
		sslVerify = true

But since `git_parse_maybe_bool()` already takes care of handling that case (in which case we do not even want to call `git_parse_maybe_bool()`), you can limit that function to handling the command-line semantics.

So with those confusingly disagreeing semantics, I see not only myself, but other readers doing very, very well, indeed, with a code comment that explains under what circumstances we expect this callback to be called with `value == NULL`.

Show 10 quoted lines
> +}
> +
>  static int rebase_config(const char *var, const char *value, void *data)
>  {
>  	struct rebase_options *opts = data;
> @@ -815,6 +829,13 @@ static int rebase_config(const char *var, const char *value, void *data)
>  		return 0;
>  	}
>
> +	if (!strcmp(var, "rebase.merges") && value && *value) {
Why do we require a non-empty `value` here?
	[rebase]
		merges
should be equivalent to `true`,
	[rebase]
		merges =

should probably be equivalent to `false`, and both are handled correctly by `git_parse_maybe_bool()`.

Show 25 quoted lines
> +		opts->rebase_merges = git_parse_maybe_bool(value);
> +		if (opts->rebase_merges < 0)
> +			parse_merges_value(opts, value);
> +		return 0;
> +	}
> +
>  	if (!strcmp(var, "rebase.backend")) {
>  		return git_config_string(&opts->default_backend, var, value);
>  	}
> @@ -980,6 +1001,18 @@ static int parse_opt_empty(const struct option *opt, const char *arg, int unset)
>  	return 0;
>  }
>
> +static int parse_opt_merges(const struct option *opt, const char *arg, int unset)
> +{
> +	struct rebase_options *options = opt->value;
> +
> +	if (unset)
> +		options->rebase_merges = 0;
> +	else
> +		parse_merges_value(options, arg);
> +
> +	return 0;
> +}
> +

It is kind of inelegant to require a _second_ callback for the command-line parsing, but I guess if we want a `--no-rebase-merges` option to override a config setting, we cannot help it.

Show 144 quoted lines
>  static void NORETURN error_on_missing_default_upstream(void)
>  {
>  	struct branch *current_branch = branch_get(NULL);
> @@ -1035,7 +1068,6 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
>  	struct object_id branch_base;
>  	int ignore_whitespace = 0;
>  	const char *gpg_sign = NULL;
> -	const char *rebase_merges = NULL;
>  	struct string_list strategy_options = STRING_LIST_INIT_NODUP;
>  	struct object_id squash_onto;
>  	char *squash_onto_name = NULL;
> @@ -1137,10 +1169,9 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
>  			   &options.allow_empty_message,
>  			   N_("allow rebasing commits with empty messages"),
>  			   PARSE_OPT_HIDDEN),
> -		{OPTION_STRING, 'r', "rebase-merges", &rebase_merges,
> -			N_("mode"),
> +		OPT_CALLBACK_F('r', "rebase-merges", &options, N_("mode"),
>  			N_("try to rebase merges instead of skipping them"),
> -			PARSE_OPT_OPTARG, NULL, (intptr_t)"no-rebase-cousins"},
> +			PARSE_OPT_OPTARG, parse_opt_merges),
>  		OPT_BOOL(0, "fork-point", &options.fork_point,
>  			 N_("use 'merge-base --fork-point' to refine upstream")),
>  		OPT_STRING('s', "strategy", &options.strategy,
> @@ -1436,14 +1467,8 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
>  	if (options.exec.nr)
>  		imply_merge(&options, "--exec");
>
> -	if (rebase_merges) {
> -		if (!strcmp("rebase-cousins", rebase_merges))
> -			options.rebase_cousins = 1;
> -		else if (strcmp("no-rebase-cousins", rebase_merges))
> -			die(_("Unknown mode: %s"), rebase_merges);
> -		options.rebase_merges = 1;
> +	if (options.rebase_merges)
>  		imply_merge(&options, "--rebase-merges");
> -	}
>
>  	if (options.type == REBASE_APPLY) {
>  		if (ignore_whitespace)
> diff --git a/t/t3430-rebase-merges.sh b/t/t3430-rebase-merges.sh
> index c73949df18..d4b0e8fd49 100755
> --- a/t/t3430-rebase-merges.sh
> +++ b/t/t3430-rebase-merges.sh
> @@ -284,6 +284,102 @@ test_expect_success '--rebase-merges="" is invalid syntax' '
>  	test_cmp expect actual
>  '
>
> +test_expect_success 'rebase.merges="" is equivalent to not passing --rebase-merges' '
> +	test_config rebase.merges "" &&
> +	git checkout -b config-merges-blank E &&
> +	git rebase C &&
> +	test_cmp_graph C.. <<-\EOF
> +	* B
> +	* D
> +	o C
> +	EOF
> +'
> +
> +test_expect_success 'rebase.merges=rebase-cousins is equivalent to --rebase-merges=rebase-cousins' '
> +	test_config rebase.merges rebase-cousins &&
> +	git checkout -b config-rebase-cousins main &&
> +	git rebase HEAD^ &&
> +	test_cmp_graph HEAD^.. <<-\EOF
> +	*   Merge the topic branch '\''onebranch'\''
> +	|\
> +	| * D
> +	| * G
> +	|/
> +	o H
> +	EOF
> +'
> +
> +test_expect_success '--no-rebase-merges overrides rebase.merges=no-rebase-cousins' '
> +	test_config rebase.merges no-rebase-cousins &&
> +	git checkout -b override-config-no-rebase-cousins E &&
> +	git rebase --no-rebase-merges C &&
> +	test_cmp_graph C.. <<-\EOF
> +	* B
> +	* D
> +	o C
> +	EOF
> +'
> +
> +test_expect_success '--rebase-merges=no-rebase-cousins overrides rebase.merges=rebase-cousins' '
> +	test_config rebase.merges rebase-cousins &&
> +	git checkout -b override-config-rebase-cousins main &&
> +	git rebase --rebase-merges=no-rebase-cousins HEAD^ &&
> +	test_cmp_graph HEAD^.. <<-\EOF
> +	*   Merge the topic branch '\''onebranch'\''
> +	|\
> +	| * D
> +	| * G
> +	o | H
> +	|/
> +	o A
> +	EOF
> +'
> +
> +test_expect_success '--rebase-merges overrides rebase.merges=false' '
> +	test_config rebase.merges false &&
> +	git checkout -b override-config-merges-false E &&
> +	before="$(git rev-parse --verify HEAD)" &&
> +	test_tick &&
> +	git rebase --rebase-merges C &&
> +	test_cmp_rev HEAD $before
> +'
> +
> +test_expect_success '--rebase-merges does not override rebase.merges=rebase-cousins' '
> +	test_config rebase.merges rebase-cousins &&
> +	git checkout -b no-override-config-rebase-cousins main &&
> +	git rebase --rebase-merges HEAD^ &&
> +	test_cmp_graph HEAD^.. <<-\EOF
> +	*   Merge the topic branch '\''onebranch'\''
> +	|\
> +	| * D
> +	| * G
> +	|/
> +	o H
> +	EOF
> +'
> +
> +test_expect_success 'local rebase.merges=false overrides global rebase.merges=true' '
> +	test_config_global rebase.merges true &&
> +	test_config rebase.merges false &&
> +	git checkout -b override-global-config E &&
> +	git rebase C &&
> +	test_cmp_graph C.. <<-\EOF
> +	* B
> +	* D
> +	o C
> +	EOF
> +'
> +
> +test_expect_success 'local rebase.merges="" does not override global rebase.merges=true' '
> +	test_config_global rebase.merges no-rebase-cousins &&
> +	test_config rebase.merges "" &&
> +	git checkout -b no-override-global-config E &&
> +	before="$(git rev-parse --verify HEAD)" &&
> +	test_tick &&
> +	git rebase C &&
> +	test_cmp_rev HEAD $before
> +'
> +

I understand the temptation to introduce exhaustive matrices that test all the different settings in all the different ways they can be specified.

However, I would much prefer to keep the tests succinct, not the least to avoid the every-increasing runtime of Git's CI. It's already taking about an order of magnitude or two too long to be reasonable.

So I'd suggest reducing the tests to a single one instead of eight: verify that `rebase.merges=no-rebase-cousins` is heeded, and that `--no-rebase-cousins` overrides that. That should be plenty sufficient to prevent regressions.

Ciao, Johannes

Show 7 quoted lines
>  test_expect_success 'refs/rewritten/* is worktree-local' '
>  	git worktree add wt &&
>  	cat >wt/script-from-scratch <<-\EOF &&
> --
> 2.39.2
>
>
Previous: Alex HenrieNext: Alex Henrie
Message 15 of 96 in “rebase: add documentation and test for --no-rebase-merges”
  1. 1/3 rebase: add documentation and test for --no-rebase-mergesAlex Henrie, Feb 23, 2023
  2. 2/3 rebase: stop accepting --rebase-merges=""Alex Henrie, Feb 23, 2023
  3. Johannes SchindelinFeb 24, 2023
  4. Junio C HamanoFeb 24, 2023
  5. Alex HenrieFeb 24, 2023
  6. Junio C HamanoFeb 24, 2023
  7. Alex HenrieFeb 24, 2023
  8. Junio C HamanoFeb 24, 2023
  9. Alex HenrieFeb 24, 2023
  10. Junio C HamanoFeb 24, 2023
  11. Alex HenrieFeb 24, 2023
  12. Phillip WoodFeb 24, 2023
  13. Alex HenrieFeb 24, 2023
  14. 3/3 rebase: add a config option for --rebase-mergesAlex Henrie, Feb 23, 2023
  15. Johannes SchindelinFeb 24, 2023
  16. Alex HenrieFeb 24, 2023
  17. Phillip WoodFeb 24, 2023
  18. Alex HenrieFeb 24, 2023
  19. Junio C HamanoFeb 23, 2023
  20. Johannes SchindelinFeb 24, 2023
  21. Junio C HamanoFeb 24, 2023
  22. Alex HenrieFeb 25, 2023
  23. 0/3 rebase: add a config option for --rebase-mergesAlex Henrie, Feb 25, 2023
  24. 1/3 rebase: add documentation and test for --no-rebase-mergesAlex Henrie, Feb 25, 2023
  25. Glen ChooMar 1, 2023
  26. 2/3 rebase: deprecate --rebase-merges=""Alex Henrie, Feb 25, 2023
  27. Glen ChooMar 1, 2023
  28. Phillip WoodMar 2, 2023
  29. Calvin WanMar 2, 2023
  30. 3/3 rebase: add a config option for --rebase-mergesAlex Henrie, Feb 25, 2023
  31. Glen ChooMar 1, 2023
  32. Phillip WoodMar 2, 2023
  33. Alex HenrieMar 4, 2023
  34. Phillip WoodMar 7, 2023
  35. Alex HenrieMar 12, 2023
  36. Phillip WoodMar 13, 2023
  37. Felipe ContrerasMar 13, 2023
  38. Junio C HamanoMar 13, 2023
  39. About replaying "evil" merges... Re: [PATCH v5 3/3] rebase: add a config option for --rebase-mergesJohannes Schindelin, Mar 24, 2023
  40. Calvin WanMar 2, 2023
  41. Alex HenrieMar 4, 2023
  42. Glen ChooMar 1, 2023
  43. Alex HenrieMar 2, 2023
  44. Alex HenrieMar 2, 2023
  45. 0/3 rebase: document, clean up, and introduce a config option for --rebase-mergesAlex Henrie, Mar 5, 2023
  46. 3/3 rebase: add a config option for --rebase-mergesAlex Henrie, Mar 5, 2023
  47. Phillip WoodMar 7, 2023
  48. Junio C HamanoMar 7, 2023
  49. Alex HenrieMar 12, 2023
  50. Glen ChooMar 8, 2023
  51. Glen ChooMar 8, 2023
  52. Alex HenrieMar 12, 2023
  53. Alex HenrieMar 15, 2023
  54. Glen ChooMar 16, 2023
  55. Felipe ContrerasMar 16, 2023
  56. Glen ChooMar 16, 2023
  57. Felipe ContrerasMar 16, 2023
  58. Alex HenrieMar 16, 2023
  59. Glen ChooMar 16, 2023
  60. Alex HenrieMar 18, 2023
  61. Johannes SchindelinMar 24, 2023
  62. Sergey OrganovMar 25, 2023
  63. 1/3 rebase: add documentation and test for --no-rebase-mergesAlex Henrie, Mar 5, 2023
  64. Sergey OrganovMar 8, 2023
  65. 2/3 rebase: deprecate --rebase-merges=""Alex Henrie, Mar 5, 2023
  66. Phillip WoodMar 7, 2023
  67. Sergey OrganovMar 5, 2023
  68. Alex HenrieMar 5, 2023
  69. Sergey OrganovMar 5, 2023
  70. Alex HenrieMar 6, 2023
  71. Sergey OrganovMar 6, 2023
  72. Junio C HamanoMar 6, 2023
  73. Junio C HamanoMar 6, 2023
  74. Phillip WoodMar 6, 2023
  75. Alex HenrieMar 6, 2023
  76. Phillip WoodMar 7, 2023
  77. Glen ChooMar 8, 2023
  78. 0/3 rebase: document, clean up, and introduce a config option for --rebase-mergesAlex Henrie, Mar 12, 2023
  79. 1/3 rebase: add documentation and test for --no-rebase-mergesAlex Henrie, Mar 12, 2023
  80. 2/3 rebase: deprecate --rebase-merges=""Alex Henrie, Mar 12, 2023
  81. 3/3 rebase: add a config option for --rebase-mergesAlex Henrie, Mar 12, 2023
  82. 0/3 rebase: document, clean up, and introduce a config option for --rebase-mergesAlex Henrie, Mar 20, 2023
  83. 1/3 rebase: add documentation and test for --no-rebase-mergesAlex Henrie, Mar 20, 2023
  84. 2/3 rebase: deprecate --rebase-merges=""Alex Henrie, Mar 20, 2023
  85. 3/3 rebase: add a config option for --rebase-mergesAlex Henrie, Mar 20, 2023
  86. Phillip WoodMar 22, 2023
  87. Junio C HamanoMar 23, 2023
  88. Phillip WoodMar 24, 2023
  89. Alex HenrieMar 25, 2023
  90. Alex HenrieMar 25, 2023
  91. 0/3 rebase: document, clean up, and introduce a config option for --rebase-mergesAlex Henrie, Mar 26, 2023
  92. 1/3 rebase: add documentation and test for --no-rebase-mergesAlex Henrie, Mar 26, 2023
  93. 2/3 rebase: deprecate --rebase-merges=""Alex Henrie, Mar 26, 2023
  94. 3/3 rebase: add a config option for --rebase-mergesAlex Henrie, Mar 26, 2023
  95. Phillip WoodMar 26, 2023
  96. Junio C HamanoMar 27, 2023

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