parse-options: catch likely typo in presense of aggregated options.

If options are aggregated, and that the whole token is an exact
prefix of a long option that is longer than 2 letters, reject
it.  This is to prevent a common typo:

	$ git commit -amend

to get interpreted as "commit all with message 'end'".

The typo check isn't performed if there is no aggregation,
because the stuck form is the recommended one.  If we have `-o`
being a valid short option that takes an argument, and --option
a long one, then we _MUST_ accept -option as "'o' option with
argument 'ption'", which is our official recommended form.

Signed-off-by: Pierre Habouzit <madcoder@debian.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

3 files changed, 40 insertions, 2 deletions

diff --git a/parse-options.c b/parse-options.c
index 7a08a0c64..d9562ba50 100644
--- a/parse-options.c
+++ b/parse-options.c
@@ -216,6 +216,26 @@ is_abbreviated:
 	return error("unknown option `%s'", arg);
 }
 
+void check_typos(const char *arg, const struct option *options)
+{
+	if (strlen(arg) < 3)
+		return;
+
+	if (!prefixcmp(arg, "no-")) {
+		error ("did you mean `--%s` (with two dashes ?)", arg);
+		exit(129);
+	}
+
+	for (; options->type != OPTION_END; options++) {
+		if (!options->long_name)
+			continue;
+		if (!prefixcmp(options->long_name, arg)) {
+			error ("did you mean `--%s` (with two dashes ?)", arg);
+			exit(129);
+		}
+	}
+}
+
 static NORETURN void usage_with_options_internal(const char * const *,
                                                  const struct option *, int);
 
@@ -235,12 +255,18 @@ int parse_options(int argc, const char **argv, const struct option *options,
 
 		if (arg[1] != '-') {
 			args.opt = arg + 1;
-			do {
+			if (*args.opt == 'h')
+				usage_with_options(usagestr, options);
+			if (parse_short_opt(&args, options) < 0)
+				usage_with_options(usagestr, options);
+			if (args.opt)
+				check_typos(arg + 1, options);
+			while (args.opt) {
 				if (*args.opt == 'h')
 					usage_with_options(usagestr, options);
 				if (parse_short_opt(&args, options) < 0)
 					usage_with_options(usagestr, options);
-			} while (args.opt);
+			}
 			continue;
 		}
 
diff --git a/t/t0040-parse-options.sh b/t/t0040-parse-options.sh
index 462fdf262..0a3b55d12 100755
--- a/t/t0040-parse-options.sh
+++ b/t/t0040-parse-options.sh
@@ -19,6 +19,7 @@ string options
                           get a string
     --string2 <str>       get another string
     --st <st>             get another string (pervert ordering)
+    -o <str>              get another string
 
 EOF
 
@@ -103,4 +104,14 @@ test_expect_success 'non ambiguous option (after two options it abbreviates)' '
 	git diff expect output
 '
 
+cat > expect.err << EOF
+error: did you mean \`--boolean\` (with two dashes ?)
+EOF
+
+test_expect_success 'detect possible typos' '
+	! test-parse-options -boolean > output 2> output.err &&
+	test ! -s output &&
+	git diff expect.err output.err
+'
+
 test_done
diff --git a/test-parse-options.c b/test-parse-options.c
index 4d3e2ec39..eed8a02c6 100644
--- a/test-parse-options.c
+++ b/test-parse-options.c
@@ -19,6 +19,7 @@ int main(int argc, const char **argv)
 		OPT_STRING('s', "string", &string, "string", "get a string"),
 		OPT_STRING(0, "string2", &string, "str", "get another string"),
 		OPT_STRING(0, "st", &string, "st", "get another string (pervert ordering)"),
+		OPT_STRING('o', NULL, &string, "str", "get another string"),
 		OPT_END(),
 	};
 	int i;