config: add --fixed-value option, un-implemented

The 'git config' builtin takes a 'value-pattern' parameter for several
actions. This can cause confusion when expecting exact value matches
instead of regex matches, especially when the input string contains
metacharacters. While callers can escape the patterns themselves, it
would be more friendly to allow an argument to disable the pattern
matching in favor of an exact string match.

Add a new '--fixed-value' option that does not currently change the
behavior. The implementation will be filled in by later changes for
each appropriate action. For now, check and test that --fixed-value
will abort the command when included with an incompatible action or
without a 'value-pattern' argument.

The name '--fixed-value' was chosen over something simpler like
'--fixed' because some commands allow regular expressions on the
key in addition to the value.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

3 files changed, 73 insertions, 7 deletions

diff --git a/Documentation/git-config.txt b/Documentation/git-config.txt
index 0be5499952..09a1d273a9 100644
--- a/Documentation/git-config.txt
+++ b/Documentation/git-config.txt
@@ -9,15 +9,15 @@ git-config - Get and set repository or global options
 SYNOPSIS
 --------
 [verse]
-'git config' [<file-option>] [--type=<type>] [--show-origin] [--show-scope] [-z|--null] name [value [value-pattern]]
+'git config' [<file-option>] [--type=<type>] [--fixed-value] [--show-origin] [--show-scope] [-z|--null] name [value [value-pattern]]
 'git config' [<file-option>] [--type=<type>] --add name value
-'git config' [<file-option>] [--type=<type>] --replace-all name value [value-pattern]
-'git config' [<file-option>] [--type=<type>] [--show-origin] [--show-scope] [-z|--null] --get name [value-pattern]
-'git config' [<file-option>] [--type=<type>] [--show-origin] [--show-scope] [-z|--null] --get-all name [value-pattern]
-'git config' [<file-option>] [--type=<type>] [--show-origin] [--show-scope] [-z|--null] [--name-only] --get-regexp name_regex [value-pattern]
+'git config' [<file-option>] [--type=<type>] [--fixed-value] --replace-all name value [value-pattern]
+'git config' [<file-option>] [--type=<type>] [--show-origin] [--show-scope] [-z|--null] [--fixed-value] --get name [value-pattern]
+'git config' [<file-option>] [--type=<type>] [--show-origin] [--show-scope] [-z|--null] [--fixed-value] --get-all name [value-pattern]
+'git config' [<file-option>] [--type=<type>] [--show-origin] [--show-scope] [-z|--null] [--fixed-value] [--name-only] --get-regexp name_regex [value-pattern]
 'git config' [<file-option>] [--type=<type>] [-z|--null] --get-urlmatch name URL
-'git config' [<file-option>] --unset name [value-pattern]
-'git config' [<file-option>] --unset-all name [value-pattern]
+'git config' [<file-option>] [--fixed-value] --unset name [value-pattern]
+'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
@@ -165,6 +165,12 @@ See also <<FILES>>.
 --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
+	the name/value pairs that are matched to only those where the value
+	is exactly equal to the `value-pattern`.
+
 --type <type>::
   'git config' will ensure that any input or output is valid under the given
   type constraint(s), and will canonicalize outgoing values in `<type>`'s
diff --git a/builtin/config.c b/builtin/config.c
index 590392c811..f1b73ac8b5 100644
--- a/builtin/config.c
+++ b/builtin/config.c
@@ -34,6 +34,7 @@ static int respect_includes_opt = -1;
 static struct config_options config_options;
 static int show_origin;
 static int show_scope;
+static int fixed_value;
 
 #define ACTION_GET (1<<0)
 #define ACTION_GET_ALL (1<<1)
@@ -144,6 +145,7 @@ static struct option builtin_config_options[] = {
 	OPT_BIT(0, "rename-section", &actions, N_("rename section: old-name new-name"), ACTION_RENAME_SECTION),
 	OPT_BIT(0, "remove-section", &actions, N_("remove a section: name"), ACTION_REMOVE_SECTION),
 	OPT_BIT('l', "list", &actions, N_("list all"), ACTION_LIST),
+	OPT_BOOL(0, "fixed-value", &fixed_value, N_("use string equality when comparing values to 'value-pattern'")),
 	OPT_BIT('e', "edit", &actions, N_("open an editor"), ACTION_EDIT),
 	OPT_BIT(0, "get-color", &actions, N_("find the color configured: slot [default]"), ACTION_GET_COLOR),
 	OPT_BIT(0, "get-colorbool", &actions, N_("find the color setting: slot [stdout-is-tty]"), ACTION_GET_COLORBOOL),
@@ -766,6 +768,40 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 		usage_builtin_config();
 	}
 
+	/* check usage of --fixed-value */
+	if (fixed_value) {
+		int allowed_usage = 0;
+
+		switch (actions) {
+		/* git config --get <name> <value-pattern> */
+		case ACTION_GET:
+		/* git config --get-all <name> <value-pattern> */
+		case ACTION_GET_ALL:
+		/* git config --get-regexp <name-pattern> <value-pattern> */
+		case ACTION_GET_REGEXP:
+		/* git config --unset <name> <value-pattern> */
+		case ACTION_UNSET:
+		/* git config --unset-all <name> <value-pattern> */
+		case ACTION_UNSET_ALL:
+			allowed_usage = argc > 1 && !!argv[1];
+			break;
+
+		/* git config <name> <value> <value-pattern> */
+		case ACTION_SET_ALL:
+		/* git config --replace-all <name> <value> <value-pattern> */
+		case ACTION_REPLACE_ALL:
+			allowed_usage = argc > 2 && !!argv[2];
+			break;
+
+		/* other options don't allow --fixed-value */
+		}
+
+		if (!allowed_usage) {
+			error(_("--fixed-value only applies with 'value-pattern'"));
+			usage_builtin_config();
+		}
+	}
+
 	if (actions & PAGING_ACTIONS)
 		setup_auto_pager("config", 1);
 
diff --git a/t/t1300-config.sh b/t/t1300-config.sh
index bddf5250dc..841ed204d6 100755
--- a/t/t1300-config.sh
+++ b/t/t1300-config.sh
@@ -1970,4 +1970,28 @@ test_expect_success '--replace-all and value-pattern' '
 	test_cmp expect actual
 '
 
+test_expect_success 'refuse --fixed-value for incompatible actions' '
+	test_when_finished rm -f config &&
+	git config --file=config dev.null bogus &&
+
+	# These modes do not allow --fixed-value at all
+	test_must_fail git config --file=config --fixed-value --add dev.null bogus &&
+	test_must_fail git config --file=config --fixed-value --get-urlmatch dev.null bogus &&
+	test_must_fail git config --file=config --fixed-value --get-urlmatch dev.null bogus &&
+	test_must_fail git config --file=config --fixed-value --rename-section dev null &&
+	test_must_fail git config --file=config --fixed-value --remove-section dev &&
+	test_must_fail git config --file=config --fixed-value --list &&
+	test_must_fail git config --file=config --fixed-value --get-color dev.null &&
+	test_must_fail git config --file=config --fixed-value --get-colorbool dev.null &&
+
+	# These modes complain when --fixed-value has no value-pattern
+	test_must_fail git config --file=config --fixed-value dev.null bogus &&
+	test_must_fail git config --file=config --fixed-value --replace-all dev.null bogus &&
+	test_must_fail git config --file=config --fixed-value --get dev.null &&
+	test_must_fail git config --file=config --fixed-value --get-all dev.null &&
+	test_must_fail git config --file=config --fixed-value --get-regexp "dev.*" &&
+	test_must_fail git config --file=config --fixed-value --unset dev.null &&
+	test_must_fail git config --file=config --fixed-value --unset-all dev.null
+'
+
 test_done