added the cwk_path_change_root function

test/root_test.c

@@ -1,6 +1,88 @@
 #include <cwalk.h>
+#include <memory.h>
+#include <stdio.h>
 #include <stdlib.h>
 
+int root_change_overlapping()
+{
+  size_t length;
+  char buffer[FILENAME_MAX] = "C:\\hello\\world.txt";
+
+  cwk_path_set_style(CWK_STYLE_WINDOWS);
+  length = cwk_path_change_root(buffer, "D:\\path\\", buffer,
+    sizeof(buffer));
+
+  if (length != 23) {
+    return EXIT_FAILURE;
+  }
+
+  if (strcmp(buffer, "D:\\path\\hello\\world.txt") != 0) {
+    return EXIT_FAILURE;
+  }
+
+  return EXIT_SUCCESS;
+}
+
+int root_change_separators()
+{
+  size_t length;
+  char buffer[FILENAME_MAX];
+
+  cwk_path_set_style(CWK_STYLE_WINDOWS);
+  length = cwk_path_change_root("C:\\hello\\world.txt", "D:\\path\\", buffer,
+    sizeof(buffer));
+
+  if (length != 23) {
+    return EXIT_FAILURE;
+  }
+
+  if (strcmp(buffer, "D:\\path\\hello\\world.txt") != 0) {
+    return EXIT_FAILURE;
+  }
+
+  return EXIT_SUCCESS;
+}
+
+int root_change_empty()
+{
+  size_t length;
+  char buffer[FILENAME_MAX];
+
+  cwk_path_set_style(CWK_STYLE_WINDOWS);
+  length = cwk_path_change_root("C:\\hello\\world.txt", "", buffer,
+    sizeof(buffer));
+
+  if (length != 15) {
+    return EXIT_FAILURE;
+  }
+
+  if (strcmp(buffer, "hello\\world.txt") != 0) {
+    return EXIT_FAILURE;
+  }
+
+  return EXIT_SUCCESS;
+}
+
+int root_change_simple()
+{
+  size_t length;
+  char buffer[FILENAME_MAX];
+
+  cwk_path_set_style(CWK_STYLE_WINDOWS);
+  length = cwk_path_change_root("C:\\hello\\world.txt", "D:\\", buffer,
+    sizeof(buffer));
+
+  if (length != 18) {
+    return EXIT_FAILURE;
+  }
+
+  if (strcmp(buffer, "D:\\hello\\world.txt") != 0) {
+    return EXIT_FAILURE;
+  }
+
+  return EXIT_SUCCESS;
+}
+
 int root_relative_windows()
 {
   size_t length;
@@ -141,7 +223,6 @@ int root_windows_slash()
   return EXIT_SUCCESS;
 }
 
-
 int root_windows_backslash()
 {
   size_t length;