Re: [PATCH 2/2] rebase: add a config option for --rebase-merges

[Phillip Wood <phillip.wood123@xxxxxxxxx>]

Hi Alex

On 20/02/2023 03:32, Alex Henrie wrote:

I think the commit message could benefit from some justification for why 
this config option is useful. I don't object to it being added but you 
need to make the case for why it is a good idea.

> At the same time, stop accepting --rebase-merges="" as a synonym of
> --rebase-merges=no-rebase-cousins.

Please try to avoid combining unrelated changes in the same patch. I 
agree that accepting an empty argument to mean "no-rebase-cousins" is 
slightly odd but as that is the default I'm not sure it is doing any harm.

Best Wishes

Phillip

> Signed-off-by: Alex Henrie <alexhenrie24@xxxxxxxxx>
> ---
>   Documentation/config/rebase.txt |  3 ++
>   builtin/rebase.c                | 50 ++++++++++++++-----
>   t/t3430-rebase-merges.sh        | 87 +++++++++++++++++++++++++++++++++
>   3 files changed, 127 insertions(+), 13 deletions(-)
>
> diff --git a/Documentation/config/rebase.txt b/Documentation/config/rebase.txt
> index f19bd0e040..d956ec4441 100644
> --- a/Documentation/config/rebase.txt
> +++ b/Documentation/config/rebase.txt
> @@ -67,3 +67,6 @@ rebase.rescheduleFailedExec::
>   
>   rebase.forkPoint::
>   	If set to false set `--no-fork-point` option by default.
> +
> +rebase.merges::
> +	Default value of `--rebase-merges` option.
> diff --git a/builtin/rebase.c b/builtin/rebase.c
> index 96c0474379..ab4c3b2870 100644
> --- a/builtin/rebase.c
> +++ b/builtin/rebase.c
> @@ -771,6 +771,25 @@ 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("drop", value)) {
> +			options->rebase_merges = 0;
> +			return;
> +		}
> +
> +		if (!strcmp("no-rebase-cousins", value))
> +			options->rebase_cousins = 0;
> +		else if (!strcmp("rebase-cousins", value))
> +			options->rebase_cousins = 1;
> +		else
> +			die(_("Unknown mode: %s"), value);
> +	}
> +
> +	options->rebase_merges = 1;
> +}
> +
>   static int rebase_config(const char *var, const char *value, void *data)
>   {
>   	struct rebase_options *opts = data;
> @@ -815,6 +834,14 @@ static int rebase_config(const char *var, const char *value, void *data)
>   		return 0;
>   	}
>   
> +	if (!strcmp(var, "rebase.merges")) {
> +		const char *rebase_merges;
> +		if (!git_config_string(&rebase_merges, var, value) &&
> +		    rebase_merges && *rebase_merges)
> +			parse_merges_value(opts, rebase_merges);
> +		return 0;
> +	}
> +
>   	if (!strcmp(var, "rebase.backend")) {
>   		return git_config_string(&opts->default_backend, var, value);
>   	}
> @@ -980,6 +1007,13 @@ 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)
> +{
> +	BUG_ON_OPT_NEG(unset);
> +	parse_merges_value(opt->value, arg);
> +	return 0;
> +}
> +
>   static void NORETURN error_on_missing_default_upstream(void)
>   {
>   	struct branch *current_branch = branch_get(NULL);
> @@ -1035,7 +1069,6 @@ 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 +1170,9 @@ 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)""},
> +			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,
> @@ -1436,16 +1468,8 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
>   	if (options.exec.nr)
>   		imply_merge(&options, "--exec");
>   
> -	if (rebase_merges && strcmp("drop", rebase_merges)) {
> -		if (!*rebase_merges)
> -			; /* default mode; do nothing */
> -		else 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 861c8405f2..9be07249cc 100755
> --- a/t/t3430-rebase-merges.sh
> +++ b/t/t3430-rebase-merges.sh
> @@ -298,6 +298,92 @@ test_expect_success 'do not rebase cousins unless asked for' '
>   	EOF
>   '
>   
> +test_expect_success '--rebase-merges="" is invalid syntax' '
> +	echo "fatal: Unknown mode: " >expect &&
> +	! git rebase --rebase-merges="" HEAD^ 2>actual &&
> +	test_cmp expect actual
> +'
> +
> +test_expect_success 'rebase.merges="" is equivalent to not passing --rebase-merges' '
> +	git 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' '
> +	git 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 '--rebase-merges=drop overrides rebase.merges=no-rebase-cousins' '
> +	git config rebase.merges no-rebase-cousins &&
> +	git checkout -b override-config-no-rebase-cousins E &&
> +	git rebase --rebase-merges=drop C &&
> +	test_cmp_graph C.. <<-\EOF
> +	* B
> +	* D
> +	o C
> +	EOF
> +'
> +
> +test_expect_success '--rebase-merges=no-rebase-cousins overrides rebase.merges=rebase-cousins' '
> +	git 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=drop' '
> +	git config rebase.merges drop &&
> +	git checkout -b override-config-merges-drop main &&
> +	git rebase --rebase-merges HEAD^ &&
> +	test_cmp_graph HEAD^.. <<-\EOF
> +	*   Merge the topic branch '\''onebranch'\''
> +	|\
> +	| * D
> +	| * G
> +	o | H
> +	|/
> +	o A
> +	EOF
> +'
> +
> +test_expect_success '--rebase-merges does not override rebase.merges=rebase-cousins' '
> +	git 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 'refs/rewritten/* is worktree-local' '
>   	git worktree add wt &&
>   	cat >wt/script-from-scratch <<-\EOF &&
> @@ -408,6 +494,7 @@ test_expect_success 'a "merge" into a root commit is a fast-forward' '
>   '
>   
>   test_expect_success 'A root commit can be a cousin, treat it that way' '
> +	git config --unset rebase.merges &&
>   	git checkout --orphan khnum &&
>   	test_commit yama &&
>   	git checkout -b asherah main &&