versionfmt/rpm: handle a tilde correctly

ext/versionfmt/rpm/parser.go

@@ -212,25 +212,11 @@ func rpmvercmp(strA, strB string) int {
 			} else if len(b) > len(a) {
 				return -1
 			}
-
 		} else if unicode.IsNumber([]rune(b)[0]) {
 			// a is alpha, b is numeric
 			return -1
 		}
 
-		// This is the last iteration.
-		if i == segs-1 {
-			// If there is a tilde in a segment past the min number of segments, find
-			// it before we rely on string compare.
-			lia := strings.LastIndex(strA, "~")
-			lib := strings.LastIndex(strB, "~")
-			if lia > lib {
-				return -1
-			} else if lia < lib {
-				return 1
-			}
-		}
-
 		// string compare
 		if a < b {
 			return -1
@@ -244,6 +230,13 @@ func rpmvercmp(strA, strB string) int {
 		return 0
 	}
 
+	// If there is a tilde in a segment past the min number of segments, find it.
+	if len(segsa) > segs && []rune(segsa[segs])[0] == '~' {
+		return -1
+	} else if len(segsb) > segs && []rune(segsb[segs])[0] == '~' {
+		return 1
+	}
+
 	// whoever has the most segments wins
 	if len(segsa) > len(segsb) {
 		return 1

ext/versionfmt/rpm/parser_test.go

@@ -162,6 +162,11 @@ func TestParseAndCompare(t *testing.T) {
 		{"1.0~rc1~git123", EQUAL, "1.0~rc1~git123"},
 		{"1.0~rc1~git123", LESS, "1.0~rc1"},
 		{"1.0~rc1", GREATER, "1.0~rc1~git123"},
+		{"1~", GREATER, "1~~"},
+		{"2~", GREATER, "1"},
+		{"1.0", GREATER, "1.0-~"},
+		{"1.0", LESS, "1.0-1~"},
+		{"~", GREATER, "~~"},
 	}
 
 	var (