Don't check JIRA ID unless branch has one

Before this change, we complained about a leading JIRA issue ID even
when the branch name didn't contain any JIRA prefix.

Author: walles

src/jira.ts

@@ -67,6 +67,10 @@ function getJiraBranchIdMismatchDiagnostic(
   }
 
   const branchIssueId = utils.getJiraIssueIdFromBranchName(gitBranch);
+  if (!branchIssueId) {
+    // No issue ID in the branch name, never mind
+    return [];
+  }
   if (docIssueId.id.toUpperCase() === branchIssueId) {
     // Text and branch match, done!
     return [];

src/test/suite/jira.test.ts

@@ -62,6 +62,16 @@ suite("JIRA Prefix Warnings", () => {
       [expected]
     );
   });
+
+  test("JIRA-123: No branch issue ID", () => {
+    assert.deepStrictEqual(
+      jira._private.getJiraBranchIdMismatchDiagnostic(
+        "holly-molly-polly",
+        "JIRA-123: No branch issue ID"
+      ),
+      []
+    );
+  });
 });
 
 suite("Quick Fix", () => {
@@ -141,6 +151,17 @@ suite("Quick Fix", () => {
     ]);
   });
 
+  test("[JIRA-123] No branch issue ID", async () => {
+    const doc = await createTextDocument(["[JIRA-123] No branch issue ID"]);
+    const actual = jira._private.createBranchIssueIdFix(
+      "tom-dick-and-harry",
+      doc,
+      utils.createRange(0, 5, 5)
+    );
+
+    assert.deepEqual(actual, []);
+  });
+
   test("[JIRA-234] Already matching the branch issue ID", async () => {
     const doc = await createTextDocument([
       "[JIRA-234] Should match branch issue ID",