builtin/config: introduce "list" subcommand

While git-config(1) has several modes, those modes are not exposed with
subcommands but instead by specifying action flags like `--unset` or
`--list`. This user interface is not really in line with how our more
modern commands work, where it is a lot more customary to say e.g. `git
remote list`. Furthermore, to add to the confusion, git-config(1) also
allows the user to request modes implicitly by just specifying the
correct number of arguments. Thus, `git config foo.bar` will retrieve
the value of "foo.bar" while `git config foo.bar baz` will set it to
"baz".

Overall, this makes for a confusing interface that could really use a
makeover. It hurts discoverability of what you can do with git-config(1)
and is comparatively easy to get wrong. Converting the command to have
subcommands instead would go a long way to help address these issues.

One concern in this context is backwards compatibility. Luckily, we can
introduce subcommands without breaking backwards compatibility at all.
This is because all the implicit modes of git-config(1) require that the
first argument is a properly formatted config key. And as config keys
_must_ have a dot in their name, any value without a dot would have been
discarded by git-config(1) previous to this change. Thus, given that
none of the subcommands do have a dot, they are unambiguous.

Introduce the first such new subcommand, which is "git config list". To
retain backwards compatibility we only conditionally use subcommands and
will fall back to the old syntax in case no subcommand was detected.
This should help to transition to the new-style syntax until we
eventually deprecate and remove the old-style syntax.

Note that the way we handle this we're duplicating some functionality
across old and new syntax. While this isn't pretty, it helps us to
ensure that there really is no change in behaviour for the old syntax.

Amend tests such that we run them both with old and new style syntax.
As tests are now run twice, state from the first run may be still be
around in the second run and thus cause tests to fail. Add cleanup logic
as required to fix such tests.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

Documentation/git-config.txt

@@ -9,6 +9,7 @@ git-config - Get and set repository or global options
 SYNOPSIS
 --------
 [verse]
+'git config list' [<file-option>] [<display-option>] [--includes]
 'git config' [<file-option>] [--type=<type>] [--comment=<message>] [--fixed-value] [--show-origin] [--show-scope] [-z|--null] <name> [<value> [<value-pattern>]]
 'git config' [<file-option>] [--type=<type>] [--comment=<message>] --add <name> <value>
 'git config' [<file-option>] [--type=<type>] [--comment=<message>] [--fixed-value] --replace-all <name> <value> [<value-pattern>]
@@ -20,7 +21,6 @@ SYNOPSIS
 'git config' [<file-option>] [--fixed-value] --unset-all <name> [<value-pattern>]
 'git config' [<file-option>] --rename-section <old-name> <new-name>
 'git config' [<file-option>] --remove-section <name>
-'git config' [<file-option>] [--show-origin] [--show-scope] [-z|--null] [--name-only] -l | --list
 'git config' [<file-option>] --get-color <name> [<default>]
 'git config' [<file-option>] --get-colorbool <name> [<stdout-is-tty>]
 'git config' [<file-option>] -e | --edit
@@ -74,6 +74,12 @@ On success, the command returns the exit code 0.
 A list of all available configuration variables can be obtained using the
 `git help --config` command.
 
+COMMANDS
+--------
+
+list::
+	List all variables set in config file, along with their values.
+
 [[OPTIONS]]
 OPTIONS
 -------
@@ -190,10 +196,6 @@ See also <<FILES>>.
 --unset-all::
 	Remove all lines matching the key from config file.
 
--l::
---list::
-	List all variables set in config file, along with their values.
-
 --fixed-value::
 	When used with the `value-pattern` argument, treat `value-pattern` as
 	an exact string instead of a regular expression. This will restrict
@@ -248,7 +250,7 @@ Valid `<type>`'s include:
 	contain line breaks.
 
 --name-only::
-	Output only the names of config variables for `--list` or
+	Output only the names of config variables for `list` or
 	`--get-regexp`.
 
 --show-origin::
@@ -300,10 +302,20 @@ Valid `<type>`'s include:
   When using `--get`, and the requested variable is not found, behave as if
   <value> were the value assigned to that variable.
 
+DEPRECATED MODES
+----------------
+
+The following modes have been deprecated in favor of subcommands. It is
+recommended to migrate to the new syntax.
+
+-l::
+--list::
+	Replaced by `git config list`.
+
 CONFIGURATION
 -------------
 `pager.config` is only respected when listing configuration, i.e., when
-using `--list` or any of the `--get-*` which may return multiple results.
+using `list` or any of the `--get-*` which may return multiple results.
 The default is to use a pager.
 
 [[FILES]]

builtin/config.c

@@ -16,10 +16,16 @@
 #include "worktree.h"
 
 static const char *const builtin_config_usage[] = {
+	N_("git config list [<file-option>] [<display-option>] [--includes]"),
 	N_("git config [<options>]"),
 	NULL
 };
 
+static const char *const builtin_config_list_usage[] = {
+	N_("git config list [<file-option>] [<display-option>] [--includes]"),
+	NULL
+};
+
 static char *key;
 static regex_t *key_regexp;
 static const char *value_pattern;
@@ -33,6 +39,7 @@ static char delim = '=';
 static char key_delim = ' ';
 static char term = '\n';
 
+static parse_opt_subcommand_fn *subcommand;
 static int use_global_config, use_system_config, use_local_config;
 static int use_worktree_config;
 static struct git_config_source given_config_source;
@@ -706,14 +713,24 @@ static void handle_nul(void) {
 	}
 }
 
+#define CONFIG_LOCATION_OPTIONS \
+	OPT_GROUP(N_("Config file location")), \
+	OPT_BOOL(0, "global", &use_global_config, N_("use global config file")), \
+	OPT_BOOL(0, "system", &use_system_config, N_("use system config file")), \
+	OPT_BOOL(0, "local", &use_local_config, N_("use repository config file")), \
+	OPT_BOOL(0, "worktree", &use_worktree_config, N_("use per-worktree config file")), \
+	OPT_STRING('f', "file", &given_config_source.file, N_("file"), N_("use given config file")), \
+	OPT_STRING(0, "blob", &given_config_source.blob, N_("blob-id"), N_("read config from given blob object"))
+
+#define CONFIG_DISPLAY_OPTIONS \
+	OPT_GROUP(N_("Display options")), \
+	OPT_BOOL('z', "null", &end_nul, N_("terminate values with NUL byte")), \
+	OPT_BOOL(0, "name-only", &omit_values, N_("show variable names only")), \
+	OPT_BOOL(0, "show-origin", &show_origin, N_("show origin of config (file, standard input, blob, command line)")), \
+	OPT_BOOL(0, "show-scope", &show_scope, N_("show scope of config (worktree, local, global, system, command)"))
+
 static struct option builtin_config_options[] = {
-	OPT_GROUP(N_("Config file location")),
-	OPT_BOOL(0, "global", &use_global_config, N_("use global config file")),
-	OPT_BOOL(0, "system", &use_system_config, N_("use system config file")),
-	OPT_BOOL(0, "local", &use_local_config, N_("use repository config file")),
-	OPT_BOOL(0, "worktree", &use_worktree_config, N_("use per-worktree config file")),
-	OPT_STRING('f', "file", &given_config_source.file, N_("file"), N_("use given config file")),
-	OPT_STRING(0, "blob", &given_config_source.blob, N_("blob-id"), N_("read config from given blob object")),
+	CONFIG_LOCATION_OPTIONS,
 	OPT_GROUP(N_("Action")),
 	OPT_CMDMODE(0, "get", &actions, N_("get value: name [<value-pattern>]"), ACTION_GET),
 	OPT_CMDMODE(0, "get-all", &actions, N_("get all values: key [<value-pattern>]"), ACTION_GET_ALL),
@@ -737,15 +754,12 @@ static struct option builtin_config_options[] = {
 	OPT_CALLBACK_VALUE(0, "bool-or-str", &type, N_("value is --bool or string"), TYPE_BOOL_OR_STR),
 	OPT_CALLBACK_VALUE(0, "path", &type, N_("value is a path (file or directory name)"), TYPE_PATH),
 	OPT_CALLBACK_VALUE(0, "expiry-date", &type, N_("value is an expiry date"), TYPE_EXPIRY_DATE),
+	CONFIG_DISPLAY_OPTIONS,
 	OPT_GROUP(N_("Other")),
-	OPT_BOOL('z', "null", &end_nul, N_("terminate values with NUL byte")),
-	OPT_BOOL(0, "name-only", &omit_values, N_("show variable names only")),
-	OPT_BOOL(0, "includes", &respect_includes_opt, N_("respect include directives on lookup")),
-	OPT_BOOL(0, "show-origin", &show_origin, N_("show origin of config (file, standard input, blob, command line)")),
-	OPT_BOOL(0, "show-scope", &show_scope, N_("show scope of config (worktree, local, global, system, command)")),
 	OPT_STRING(0, "default", &default_value, N_("value"), N_("with --get, use default value when missing entry")),
 	OPT_STRING(0, "comment", &comment_arg, N_("value"), N_("human-readable comment string (# will be prepended as needed)")),
 	OPT_BOOL(0, "fixed-value", &fixed_value, N_("use string equality when comparing values to 'value-pattern'")),
+	OPT_BOOL(0, "includes", &respect_includes_opt, N_("respect include directives on lookup")),
 	OPT_END(),
 };
 
@@ -754,6 +768,42 @@ static NORETURN void usage_builtin_config(void)
 	usage_with_options(builtin_config_usage, builtin_config_options);
 }
 
+static int cmd_config_list(int argc, const char **argv, const char *prefix)
+{
+	struct option opts[] = {
+		CONFIG_LOCATION_OPTIONS,
+		CONFIG_DISPLAY_OPTIONS,
+		OPT_GROUP(N_("Other")),
+		OPT_BOOL(0, "includes", &respect_includes_opt, N_("respect include directives on lookup")),
+		OPT_END(),
+	};
+
+	argc = parse_options(argc, argv, prefix, opts, builtin_config_list_usage, 0);
+	check_argc(argc, 0, 0);
+
+	handle_config_location(prefix);
+	handle_nul();
+
+	setup_auto_pager("config", 1);
+
+	if (config_with_options(show_all_config, NULL,
+				&given_config_source, the_repository,
+				&config_options) < 0) {
+		if (given_config_source.file)
+			die_errno(_("unable to read config file '%s'"),
+				  given_config_source.file);
+		else
+			die(_("error processing config file(s)"));
+	}
+
+	return 0;
+}
+
+static struct option builtin_subcommand_options[] = {
+	OPT_SUBCOMMAND("list", &subcommand, cmd_config_list),
+	OPT_END(),
+};
+
 int cmd_config(int argc, const char **argv, const char *prefix)
 {
 	char *value = NULL, *comment = NULL;
@@ -763,6 +813,22 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 
 	given_config_source.file = xstrdup_or_null(getenv(CONFIG_ENVIRONMENT));
 
+	/*
+	 * This is somewhat hacky: we first parse the command line while
+	 * keeping all args intact in order to determine whether a subcommand
+	 * has been specified. If so, we re-parse it a second time, but this
+	 * time we drop KEEP_ARGV0. This is so that we don't munge the command
+	 * line in case no subcommand was given, which would otherwise confuse
+	 * us when parsing the legacy-style modes that don't use subcommands.
+	 */
+	argc = parse_options(argc, argv, prefix, builtin_subcommand_options, builtin_config_usage,
+			     PARSE_OPT_SUBCOMMAND_OPTIONAL|PARSE_OPT_NO_INTERNAL_HELP|PARSE_OPT_KEEP_ARGV0|PARSE_OPT_KEEP_UNKNOWN_OPT);
+	if (subcommand) {
+		argc = parse_options(argc, argv, prefix, builtin_subcommand_options, builtin_config_usage,
+		       PARSE_OPT_SUBCOMMAND_OPTIONAL|PARSE_OPT_NO_INTERNAL_HELP|PARSE_OPT_KEEP_UNKNOWN_OPT);
+		return subcommand(argc, argv, prefix);
+	}
+
 	argc = parse_options(argc, argv, prefix, builtin_config_options,
 			     builtin_config_usage,
 			     PARSE_OPT_STOP_AT_NON_OPTION);