Allow remote polling to work with multiple simple branches

As long as the branch specs can't match multiple remote branches, then
remote polling can be used since it can (and already does) match each
branch spec against the map returned from `git ls-remote`. Add a
separate helper to determine if all branch specs are simple and use that
to determine if workspace polling is required.

src/main/java/hudson/plugins/git/GitSCM.java

@@ -664,6 +664,37 @@ private String getSingleBranch(EnvVars env) {
         return branch;
     }
 
+    /**
+     * If any branch can match a multiple remote branches, then workspace polling is required.
+     *
+     * Returns {@code true} if any branches require workspace polling.
+     */
+    private boolean branchesRequireWorkspaceForPolling(@NonNull EnvVars env, @CheckForNull TaskListener listener) {
+        for (BranchSpec branchSpec : getBranches()) {
+            final String branch = branchSpec.getName();
+            final String expandedBranch = env.expand(branch);
+
+            // If the branch contains a wildcard anywhere other than a leading */ or is empty (which is intepreted as
+            // **), it can match multiple remote branches.
+            final String strippedBranch = expandedBranch.replaceAll("^\\*/", "");
+            if (strippedBranch.equals("") || strippedBranch.contains("*")) {
+                if (listener != null) {
+                    final PrintStream log = listener.getLogger();
+
+                    if (branch.equals(expandedBranch)) {
+                        log.printf("Branch '%s' requires workspace for polling%n", branch);
+                    } else {
+                        log.printf("Branch '%s' (expanded to '%s') requires workspace for polling%n",
+                                   branch, expandedBranch);
+                    }
+                }
+                return true;
+            }
+        }
+
+        return false;
+    }
+
     @Override
     public SCMRevisionState calcRevisionsFromBuild(Run<?, ?> abstractBuild, FilePath workspace, Launcher launcher, TaskListener taskListener) throws IOException, InterruptedException {
         return SCMRevisionState.NONE;
@@ -672,17 +703,15 @@ public SCMRevisionState calcRevisionsFromBuild(Run<?, ?> abstractBuild, FilePath
     @Override
     public boolean requiresWorkspaceForPolling() {
         // TODO would need to use hudson.plugins.git.util.GitUtils.getPollEnvironment
-        return requiresWorkspaceForPolling(new EnvVars());
+        return requiresWorkspaceForPolling(new EnvVars(), null);
     }
 
     /* Package protected for test access */
-    boolean requiresWorkspaceForPolling(EnvVars environment) {
+    boolean requiresWorkspaceForPolling(EnvVars environment, TaskListener listener) {
         for (GitSCMExtension ext : getExtensions()) {
             if (ext.requiresWorkspaceForPolling()) return true;
         }
-
-        final String singleBranch = getSingleBranch(environment);
-        return singleBranch == null || singleBranch.equals("**");
+        return branchesRequireWorkspaceForPolling(environment, listener);
     }
 
     @Override
@@ -717,7 +746,7 @@ private PollingResult compareRemoteRevisionWithImpl(Job<?, ?> project, Launcher
 
         final String singleBranch = getSingleBranch(pollEnv);
 
-        if (!requiresWorkspaceForPolling(pollEnv)) {
+        if (!requiresWorkspaceForPolling(pollEnv, listener)) {
 
             final EnvVars environment = project instanceof AbstractProject<?,?> ap ? GitUtils.getPollEnvironment(ap, workspace, launcher, listener, false) : new EnvVars();
 

src/test/java/hudson/plugins/git/GitSCMTest.java

@@ -2630,6 +2630,30 @@ public void testPolling_CanDoRemotePollingIfOneBranchButMultipleRepositories() t
 		assertFalse(pollingResult.hasChanges());
 	}
 
+    @Test
+    public void testPolling_CanDoRemotePollingIfMultipleBranches() throws Exception {
+        assumeTrue("Test class max time " + MAX_SECONDS_FOR_THESE_TESTS + " exceeded", isTimeAvailable());
+        FreeStyleProject project = createFreeStyleProject();
+        List<BranchSpec> branchSpecs = Arrays.asList(
+                new BranchSpec("*/master"),
+                new BranchSpec("*/stable"));
+        GitSCM scm = new GitSCM(createRemoteRepositories(),
+                                branchSpecs, null, null,
+                                Collections.emptyList());
+        project.setScm(scm);
+        assertFalse("scm should not require workspace for polling", scm.requiresWorkspaceForPolling());
+
+        commit("commitFile1", johnDoe, "Commit number 1");
+        git.branch("stable");
+
+        FreeStyleBuild first_build = project.scheduleBuild2(0, new Cause.UserIdCause()).get();
+        r.assertBuildStatus(Result.SUCCESS, first_build);
+
+        first_build.getWorkspace().deleteContents();
+        PollingResult pollingResult = scm.poll(project, null, first_build.getWorkspace(), listener, null);
+        assertFalse(pollingResult.hasChanges());
+    }
+
     @Issue("JENKINS-24467")
     @Test
     public void testPolling_environmentValueAsEnvironmentContributingAction() throws Exception {

src/test/java/hudson/plugins/git/GitSCMUnitTest.java

@@ -261,6 +261,30 @@ public void testRequiresWorkspaceForPollingMultiBranch() throws Exception {
         List<BranchSpec> branches = new ArrayList<>();
         branches.add(new BranchSpec("master"));
         branches.add(new BranchSpec("origin/master"));
+        GitSCM bigGitSCM = new GitSCM(createRepoList(repoURL, null),
+                branches,
+                null, null, Collections.emptyList());
+        assertFalse(bigGitSCM.requiresWorkspaceForPolling());
+    }
+
+    @Test
+    public void testRequiresWorkspaceForPollingMultiBranchWithWildcardRemoteName() throws Exception {
+        /* Multi-branch use case */
+        List<BranchSpec> branches = new ArrayList<>();
+        branches.add(new BranchSpec("master"));
+        branches.add(new BranchSpec("*/master"));
+        GitSCM bigGitSCM = new GitSCM(createRepoList(repoURL, null),
+                branches,
+                null, null, Collections.emptyList());
+        assertFalse(bigGitSCM.requiresWorkspaceForPolling());
+    }
+
+    @Test
+    public void testRequiresWorkspaceForPollingMultiBranchWithWildcardSuffix() throws Exception {
+        /* Multi-branch use case */
+        List<BranchSpec> branches = new ArrayList<>();
+        branches.add(new BranchSpec("master"));
+        branches.add(new BranchSpec("*/stable*"));
         GitSCM bigGitSCM = new GitSCM(createRepoList(repoURL, null),
                 branches,
                 null, null, Collections.emptyList());
@@ -275,7 +299,7 @@ public void testRequiresWorkspaceForPollingEmptyBranchName() throws Exception {
         GitSCM bigGitSCM = new GitSCM(createRepoList(repoURL, null),
                 Collections.singletonList(new BranchSpec("${A}")),
                 null, null, Collections.emptyList());
-        assertTrue(bigGitSCM.requiresWorkspaceForPolling(env));
+        assertTrue(bigGitSCM.requiresWorkspaceForPolling(env, null));
     }
 
     @Test