Implement documented wildcard escaping in wnmatch_sub

cmdline/selftest.c

@@ -863,6 +863,24 @@ struct {
 	{ "Movies*", "Movies4", 0, 0 },
 	{ "Movies*", "Movies4/file.mkv", 0, 1 },
 
+	/* escaping of wildcard metacharacters */
+	{ "foo\\*bar", "foo*bar", 0, 0 },
+	{ "foo\\?bar", "foo?bar", 0, 0 },
+	{ "foo\\[bar", "foo[bar", 0, 0 },
+	{ "foo\\]bar", "foo]bar", 0, 0 },
+	{ "foo\\\\bar", "foo\\bar", 0, 0 },
+	{ "foo\\*bar", "fooXXXbar", 0, 1 },
+	{ "foo\\?bar", "fooXbar", 0, 1 },
+	{ "foo\\[bar", "fooXbar", 0, 1 },
+	{ "foo\\]bar", "fooXbar", 0, 1 },
+	{ "foo*bar", "fooXXXbar", 0, 0 },
+	{ "foo?bar", "fooXbar", 0, 0 },
+	{ "foo[abc]bar", "fooabar", 0, 0 },
+	{ "foo\\abar", "foo\\abar", 0, 0 },
+	{ "foo\\abar", "fooabar", 0, 1 },
+	{ "foo\\", "foo\\", 0, 0 },
+	{ "foo\\", "foo", 0, 1 },
+
 	{ 0 }
 };
 

cmdline/str.c

@@ -360,12 +360,38 @@ static inline int wnmatch_end(const char* t, int match_sub)
 	}
 }
 
+static inline int is_wild_escape(char c)
+{
+	return c == '*'
+	       || c == '?'
+	       || c == '['
+	       || c == ']'
+	       || c == '\\';
+}
+
 int wnmatch_sub(const char* p, const char* t, int match_sub)
 {
 	char p1 = 0; /* previous char */
 	while (*p) {
 		char p0 = *p;
 		switch (p0) {
+		case '\\' :
+			/*
+			 * Escape wildcard metacharacters.
+			 *
+			 * '\' is the canonical internal escape character.
+			 * On Windows, pathimport() converts the external '^'
+			 * escape syntax to this form before matching.
+			 */
+			if (is_wild_escape(p[1]))
+				++p;
+
+			if (*t == 0 || !char_match(*p, *t))
+				return 1;
+
+			++p;
+			++t;
+			break;
 		case '?' :
 			/* ? matches any single character except / */
 			if (*t == 0 || *t == '/')

cmdline/str.h

@@ -127,6 +127,7 @@ unsigned strtou(const char* nptr, char** endptr, int base);
  * - ** (not near a /) like *
  * - ##/ reduces to nothing in addition to the normal matching of ** (using # instead of * to not mess the C comment)
  * - [...] matches character classes with support for ranges and negation lile [!...] or [^...], except /
+ * - \ escapes *, ?, [, ], and \
  *
  * \return 0 if it matches
  */