Tests/syntax: produce tmp file when result doesn't match the baseline (#15089)

* Tests/syntax: produce tmp file when result doesn't match baselines

* Delete tmp file when results matches

* Rename tmp -> actual

* Ignore tmp files in git

tests/service/SyntaxTreeTests.fs

@@ -176,7 +176,9 @@ let ParseFile fileName =
             $"%A{ast}\n\n%s{diagnostics}"
         |> normalize
         |> sprintf "%s\n"
+
     let bslPath = $"{fullPath}.bsl"
+    let actualPath = $"{fullPath}.actual"
 
     let expected =
         if File.Exists bslPath then
@@ -184,9 +186,14 @@ let ParseFile fileName =
         else
             "No baseline was found"
 
+    let equals = expected = actual
     let testUpdateBSLEnv = System.Environment.GetEnvironmentVariable("TEST_UPDATE_BSL")
 
     if not (isNull testUpdateBSLEnv) && testUpdateBSLEnv.Trim() = "1" then
         File.WriteAllText(bslPath, actual)
+    elif not equals then
+        File.WriteAllText(actualPath, actual)
+    else
+        File.Delete(actualPath)
 
     Assert.AreEqual(expected, actual)

tests/service/data/SyntaxTree/.gitignore

+*.actual