Incorrect merging of border declarations

[andyjansson]

As originally reported here:

Case 1

Input

.merge-longhand {
  border: 1px solid black;
  border-top-width: 2px;
  border-right-width: 2px;
  border-bottom-width: 2px;
}

Output

.merge-longhand {
  border: 2px solid black;
  border-left: solid black;
  border-width: 1px;
}

Expected

.merge-longhand {
  border: solid black;
  border-width: 2px 2px 2px 1px;
}

Case 2

Input

.merge-longhand {
  border: none;
  border-top: 6px solid #000;
  border-bottom: 1px solid #fff;
}

Output

.merge-longhand {
  border: 6px solid #000;
  border-left: none;
  border-right: none;
}

Expected

.merge-longhand {
  border: none;
  border-top: 6px solid #000;
  border-bottom: 1px solid #fff;
}

Thanks to @apriljunge and @implico for reporting these issues.