Merge branch 'hn/config-typo-advice' into seen

"git config foo.bar=baz" is not likely to be a request to read the
value of such a variable with '=' in its name; rather it is plausible
that the user meant "git config set foo.bar baz".  Give advice when
giving an error message.

* hn/config-typo-advice:
  config: improve diagnostic for "set" with missing value
  config: add git_config_key_is_valid() for quiet validation

builtin/config.c

@@ -1,6 +1,7 @@
 #define USE_THE_REPOSITORY_VARIABLE
 #include "builtin.h"
 #include "abspath.h"
+#include "advice.h"
 #include "config.h"
 #include "color.h"
 #include "date.h"
@@ -210,6 +211,26 @@ static void check_argc(int argc, int min, int max)
 	exit(129);
 }
 
+static NORETURN void die_missing_set_value(const char *arg)
+{
+	const char *last_dot = strrchr(arg, '.');
+	const char *eq = last_dot ? strchr(last_dot + 1, '=') : NULL;
+	char *prefix = eq ? xstrndup(arg, eq - arg) : NULL;
+
+	if (prefix && git_config_key_is_valid(prefix)) {
+		error(_("missing value to set to the variable '%s'"), arg);
+		advise(_("did you mean \"git config set %s %s\"?"),
+		       prefix, eq + 1);
+	} else if (git_config_key_is_valid(arg)) {
+		error(_("missing value to set to the variable '%s'"), arg);
+	} else {
+		error(_("missing value to set to a variable with an invalid name '%s'"),
+		      arg);
+	}
+	free(prefix);
+	exit(129);
+}
+
 static void show_config_origin(const struct config_display_options *opts,
 			       const struct key_value_info *kvi,
 			       struct strbuf *buf)
@@ -1133,6 +1154,8 @@ static int cmd_config_set(int argc, const char **argv, const char *prefix,
 
 	argc = parse_options(argc, argv, prefix, opts, builtin_config_set_usage,
 			     PARSE_OPT_STOP_AT_NON_OPTION);
+	if (argc == 1)
+		die_missing_set_value(argv[0]);
 	check_argc(argc, 2, 2);
 
 	if ((flags & CONFIG_FLAGS_FIXED_VALUE) && !value_pattern)
@@ -1371,6 +1394,7 @@ static int cmd_config_actions(int argc, const char **argv, const char *prefix)
 	};
 	char *value = NULL, *comment = NULL;
 	int ret = 0;
+	int actions_implicit;
 	struct key_value_info default_kvi = KVI_INIT;
 
 	argc = parse_options(argc, argv, prefix, opts,
@@ -1385,7 +1409,8 @@ static int cmd_config_actions(int argc, const char **argv, const char *prefix)
 		exit(129);
 	}
 
-	if (actions == 0)
+	actions_implicit = (actions == 0);
+	if (actions_implicit)
 		switch (argc) {
 		case 1: actions = ACTION_GET; break;
 		case 2: actions = ACTION_SET; break;
@@ -1394,6 +1419,11 @@ static int cmd_config_actions(int argc, const char **argv, const char *prefix)
 			error(_("no action specified"));
 			exit(129);
 		}
+	if (actions_implicit && argc == 1) {
+		const char *last_dot = strrchr(argv[0], '.');
+		if (last_dot && strchr(last_dot + 1, '='))
+			die_missing_set_value(argv[0]);
+	}
 	if (display_opts.omit_values &&
 	    !(actions == ACTION_LIST || actions == ACTION_GET_REGEXP)) {
 		error(_("--name-only is only applicable to --list or --get-regexp"));

config.c

@@ -536,11 +536,14 @@ static inline int iskeychar(int c)
  * -2 if there is no section name in the key.
  *
  * store_key - pointer to char* which will hold a copy of the key with
- *             lowercase section and variable name
+ *             lowercase section and variable name, can be NULL to skip
+ *             allocation when only validation is needed
  * baselen - pointer to size_t which will hold the length of the
  *           section + subsection part, can be NULL
+ * quiet - when non-zero, suppress error() reports on rejection
  */
-int git_config_parse_key(const char *key, char **store_key, size_t *baselen_)
+static int do_parse_config_key(const char *key, char **store_key,
+			       size_t *baselen_, int quiet)
 {
 	size_t i, baselen;
 	int dot;
@@ -552,12 +555,14 @@ int git_config_parse_key(const char *key, char **store_key, size_t *baselen_)
 	 */
 
 	if (last_dot == NULL || last_dot == key) {
-		error(_("key does not contain a section: %s"), key);
+		if (!quiet)
+			error(_("key does not contain a section: %s"), key);
 		return -CONFIG_NO_SECTION_OR_NAME;
 	}
 
 	if (!last_dot[1]) {
-		error(_("key does not contain variable name: %s"), key);
+		if (!quiet)
+			error(_("key does not contain variable name: %s"), key);
 		return -CONFIG_NO_SECTION_OR_NAME;
 	}
 
@@ -568,7 +573,8 @@ int git_config_parse_key(const char *key, char **store_key, size_t *baselen_)
 	/*
 	 * Validate the key and while at it, lower case it for matching.
 	 */
-	*store_key = xmallocz(strlen(key));
+	if (store_key)
+		*store_key = xmallocz(strlen(key));
 
 	dot = 0;
 	for (i = 0; key[i]; i++) {
@@ -579,24 +585,38 @@ int git_config_parse_key(const char *key, char **store_key, size_t *baselen_)
 		if (!dot || i > baselen) {
 			if (!iskeychar(c) ||
 			    (i == baselen + 1 && !isalpha(c))) {
-				error(_("invalid key: %s"), key);
+				if (!quiet)
+					error(_("invalid key: %s"), key);
 				goto out_free_ret_1;
 			}
 			c = tolower(c);
 		} else if (c == '\n') {
-			error(_("invalid key (newline): %s"), key);
+			if (!quiet)
+				error(_("invalid key (newline): %s"), key);
 			goto out_free_ret_1;
 		}
-		(*store_key)[i] = c;
+		if (store_key)
+			(*store_key)[i] = c;
 	}
 
 	return 0;
 
 out_free_ret_1:
-	FREE_AND_NULL(*store_key);
+	if (store_key)
+		FREE_AND_NULL(*store_key);
 	return -CONFIG_INVALID_KEY;
 }
 
+int git_config_parse_key(const char *key, char **store_key, size_t *baselen_)
+{
+	return do_parse_config_key(key, store_key, baselen_, 0);
+}
+
+int git_config_key_is_valid(const char *key)
+{
+	return !do_parse_config_key(key, NULL, NULL, 1);
+}
+
 static int config_parse_pair(const char *key, const char *value,
 			     struct key_value_info *kvi,
 			     config_fn_t fn, void *data)

config.h

@@ -343,6 +343,8 @@ void repo_config_set(struct repository *, const char *, const char *);
 
 int git_config_parse_key(const char *, char **, size_t *);
 
+int git_config_key_is_valid(const char *);
+
 /*
  * The following macros specify flag bits that alter the behavior
  * of the repo_config_set_multivar*() methods.

t/t1300-config.sh

@@ -469,6 +469,62 @@ test_expect_success 'invalid key' '
 	test_must_fail git config inval.2key blabla
 '
 
+test_expect_success 'set with 1 arg of "key=value": valid key suggests split form' '
+	test_must_fail git config set pull.rebase=false 2>err &&
+	test_grep "missing value to set to the variable .pull\\.rebase=false." err &&
+	test_grep "did you mean .git config set pull\\.rebase false." err
+'
+
+test_expect_success 'set with 1 arg of "key=value": implicit form suggests split form' '
+	test_must_fail git config pull.rebase=false 2>err &&
+	test_grep "missing value to set to the variable .pull\\.rebase=false." err &&
+	test_grep "did you mean .git config set pull\\.rebase false." err
+'
+
+test_expect_success 'set with 1 arg of "key=value": invalid key does not suggest split form' '
+	test_must_fail git config set foo=bar 2>err &&
+	test_grep "missing value to set to a variable with an invalid name .foo=bar." err &&
+	test_grep ! "did you mean" err
+'
+
+test_expect_success 'set with 1 arg: variable name starting with digit is invalid' '
+	test_must_fail git config set foo.1bar=baz 2>err &&
+	test_grep "missing value to set to a variable with an invalid name .foo\\.1bar=baz." err &&
+	test_grep ! "did you mean" err
+'
+
+test_expect_success 'set with 1 arg: digit-led section name is valid' '
+	test_must_fail git config set 1foo.bar=baz 2>err &&
+	test_grep "missing value to set to the variable .1foo\\.bar=baz." err &&
+	test_grep "did you mean .git config set 1foo\\.bar baz." err
+'
+
+test_expect_success 'set with 1 arg: subsection plus invalid variable name' '
+	test_must_fail git config set foo.some.b_r=baz 2>err &&
+	test_grep "missing value to set to a variable with an invalid name .foo\\.some\\.b_r=baz." err &&
+	test_grep ! "did you mean" err
+'
+
+test_expect_success 'set with 1 arg of valid key reports missing value' '
+	test_must_fail git config set pull.rebase 2>err &&
+	test_grep "missing value to set to the variable .pull\\.rebase." err &&
+	test_grep ! "did you mean" err
+'
+
+test_expect_success 'set with 2 args including "=" in invalid key does not suggest' '
+	test_must_fail git config set pull.rebase=false true 2>err &&
+	test_grep "invalid key: pull\\.rebase=false" err &&
+	test_grep ! "did you mean" err
+'
+
+test_expect_success '"=" inside subsection is valid' '
+	test_when_finished "rm -f subsection.cfg" &&
+	git config set -f subsection.cfg foo.bar=baz.boo qux &&
+	echo qux >expect &&
+	git config get -f subsection.cfg foo.bar=baz.boo >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'correct key' '
 	git config 123456.a123 987
 '