Allow relative hashes in table references

CHANGELOG.md

@@ -19,6 +19,8 @@ as necessary. Empty sections will not end in the release notes.
 - Introduces sizing of the Nessie object cache using a relative value of the max Java heap size.
   The defaults have been changed to 70% of the Java max heap size (from the previous default of 64MB).
   If a fixed cache size setting has been explicitly configured, consider to change it to the fraction based one.
+- Relative hashes are now supported in table references, thus allowing SQL queries to specify a relative hash
+  in the `FROM` clause, e.g. `FROM table1@main#1234^1`.
 
 ### Deprecations
 

api/model/src/main/java/org/projectnessie/model/TableReference.java

@@ -127,7 +127,7 @@ public static TableReference parse(String tableReference) {
       b.reference(refName);
     }
     if (hashOrTimestamp != null) {
-      if (Validation.isValidHash(hashOrTimestamp)) {
+      if (Validation.isValidHashOrRelativeSpec(hashOrTimestamp)) {
         b.hash(hashOrTimestamp);
       } else {
         b.timestamp(hashOrTimestamp);

api/model/src/test/java/org/projectnessie/model/TestTableReference.java

@@ -45,6 +45,37 @@ static List<Object[]> fromContentKeyTestCases() {
           "12345678abcdef12345678abcdef",
           null
         },
+        // relative hashes - unambiguous
+        new Object[] {
+          "`simple_name@ref#12345678abcdef12345678abcdef~1^2*2023-09-28T12:34:56.789Z`",
+          "simple_name",
+          "ref",
+          "12345678abcdef12345678abcdef~1^2*2023-09-28T12:34:56.789Z",
+          null
+        },
+        new Object[] {
+          "`simple_name#12345678abcdef12345678abcdef~1^2*2023-09-28T12:34:56.789Z`",
+          "simple_name",
+          null,
+          "12345678abcdef12345678abcdef~1^2*2023-09-28T12:34:56.789Z",
+          null
+        },
+        // relative hashes - ambiguous
+        new Object[] {
+          "`simple_name@ref#~1^2*2023-09-28T12:34:56.789Z`",
+          "simple_name",
+          "ref",
+          "~1^2*2023-09-28T12:34:56.789Z",
+          null
+        },
+        new Object[] {
+          "`simple_name#~1^2*2023-09-28T12:34:56.789Z`",
+          "simple_name",
+          null,
+          "~1^2*2023-09-28T12:34:56.789Z",
+          null
+        },
+        // timestamps
         new Object[] {"`simple_name#2020-12-24`", "simple_name", null, null, "2020-12-24"},
         new Object[] {"`simple_name@ref#2020-12-24`", "simple_name", "ref", null, "2020-12-24"});
   }