Add git_buf_unescape and git__unescape to unescape all characters in a string (in-place)

src/attr_file.c

@@ -426,17 +426,7 @@ int git_attr_fnmatch__parse(
 		return -1;
 	} else {
 		/* strip '\' that might have be used for internal whitespace */
-		char *to = spec->pattern;
-		for (scan = spec->pattern; *scan; to++, scan++) {
-			if (*scan == '\\')
-				scan++; /* skip '\' but include next char */
-			if (to != scan)
-				*to = *scan;
-		}
-		if (to != scan) {
-			*to = '\0';
-			spec->length = (to - spec->pattern);
-		}
+		spec->length = git__unescape(spec->pattern);
 	}
 
 	return 0;

src/buffer.c

@@ -496,3 +496,7 @@ bool git_buf_is_binary(const git_buf *buf)
 	return ((printable >> 7) < nonprintable);
 }
 
+void git_buf_unescape(git_buf *buf)
+{
+	buf->size = git__unescape(buf->ptr);
+}

src/buffer.h

@@ -151,4 +151,7 @@ int git_buf_common_prefix(git_buf *buf, const git_strarray *strings);
 /* Check if buffer looks like it contains binary data */
 bool git_buf_is_binary(const git_buf *buf);
 
+/* Unescape all characters in a buffer */
+void git_buf_unescape(git_buf *buf);
+
 #endif

src/util.c

@@ -435,3 +435,21 @@ int git__parse_bool(int *out, const char *value)
 
 	return -1;
 }
+
+size_t git__unescape(char *str)
+{
+	char *scan, *pos = str;
+
+	for (scan = str; *scan; pos++, scan++) {
+		if (*scan == '\\' && *(scan + 1) != '\0')
+			scan++; /* skip '\' but include next char */
+		if (pos != scan)
+			*pos = *scan;
+	}
+
+	if (pos != scan) {
+		*pos = '\0';
+	}
+
+	return (pos - str);
+}

src/util.h

@@ -238,4 +238,13 @@ extern int git__parse_bool(int *out, const char *value);
  */
 int git__date_parse(git_time_t *out, const char *date);
 
+/*
+ * Unescapes a string in-place.
+ * 
+ * Edge cases behavior:
+ * - "jackie\" -> "jacky\"
+ * - "chan\\" -> "chan\"
+ */
+extern size_t git__unescape(char *str);
+
 #endif /* INCLUDE_util_h__ */

tests-clar/core/buffer.c

@@ -658,3 +658,23 @@ void test_core_buffer__puts_escaped(void)
 
 	git_buf_free(&a);
 }
+
+static void assert_unescape(char *expected, char *to_unescape) {
+	git_buf buf = GIT_BUF_INIT;
+
+	cl_git_pass(git_buf_sets(&buf, to_unescape));
+	git_buf_unescape(&buf);
+	cl_assert_equal_s(expected, buf.ptr);
+	cl_assert_equal_i(strlen(expected), buf.size);
+
+	git_buf_free(&buf);
+}
+
+void test_core_buffer__unescape(void)
+{
+	assert_unescape("Escaped\\", "Es\\ca\\ped\\");
+	assert_unescape("Es\\caped\\", "Es\\\\ca\\ped\\\\");
+	assert_unescape("\\", "\\");
+	assert_unescape("\\", "\\\\");
+	assert_unescape("", "");
+}