[JENKINS-42487] Exclude git repository from being polled for changes.

Author: per-bohlin

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

@@ -29,6 +29,7 @@
 import hudson.plugins.git.extensions.impl.PathRestriction;
 import hudson.plugins.git.extensions.impl.LocalBranch;
 import hudson.plugins.git.extensions.impl.PreBuildMerge;
+import hudson.plugins.git.extensions.impl.PollExclusion;
 import hudson.plugins.git.opt.PreBuildMergeOptions;
 import hudson.plugins.git.util.Build;
 import hudson.plugins.git.util.*;
@@ -597,9 +598,17 @@ public PollingResult compareRemoteRevisionWith(Job<?, ?> project, Launcher launc
     private PollingResult compareRemoteRevisionWithImpl(Job<?, ?> project, Launcher launcher, FilePath workspace, final TaskListener listener) throws IOException, InterruptedException {
         // Poll for changes. Are there any unbuilt revisions that Hudson ought to build ?
 
+        if (getExtensions().get(PollExclusion.class) != null) {
+            for (UserRemoteConfig userRemoteConfig: userRemoteConfigs) {
+                    listener.getLogger().println("Polling disabled for " + userRemoteConfig.toString());
+            }
+            return NO_CHANGES;
+        }
+
         listener.getLogger().println("Using strategy: " + getBuildChooser().getDisplayName());
 
         final Run lastBuild = project.getLastBuild();
+
         if (lastBuild == null) {
             // If we've never been built before, well, gotta build!
             listener.getLogger().println("[poll] No previous build, so forcing an initial build.");
@@ -616,7 +625,7 @@ private PollingResult compareRemoteRevisionWithImpl(Job<?, ?> project, Launcher
         final String singleBranch = getSingleBranch(pollEnv);
 
         if (!requiresWorkspaceForPolling(pollEnv)) {
-
+            listener.getLogger().println("Workspace: not required");
             final EnvVars environment = project instanceof AbstractProject ? GitUtils.getPollEnvironment((AbstractProject) project, workspace, launcher, listener, false) : new EnvVars();
 
             GitClient git = createClient(listener, environment, project, Jenkins.getInstance(), null);
@@ -684,13 +693,16 @@ private PollingResult compareRemoteRevisionWithImpl(Job<?, ?> project, Launcher
             return NO_CHANGES;
         }
 
+        listener.getLogger().println("Workspace: required");
+
         final Node node = GitUtils.workspaceToNode(workspace);
         final EnvVars environment = project instanceof AbstractProject ? GitUtils.getPollEnvironment((AbstractProject) project, workspace, launcher, listener) : project.getEnvironment(node, listener);
 
         FilePath workingDirectory = workingDirectory(project,workspace,environment,listener);
 
         // (Re)build if the working directory doesn't exist
         if (workingDirectory == null || !workingDirectory.exists()) {
+            listener.getLogger().println("Workspace missing: Building");
             return BUILD_NOW;
         }
 

src/main/java/hudson/plugins/git/extensions/impl/PollExclusion.java

@@ -0,0 +1,44 @@
+package hudson.plugins.git.extensions.impl;
+
+import hudson.Extension;
+import hudson.model.TaskListener;
+import hudson.plugins.git.GitChangeSet;
+import hudson.plugins.git.GitSCM;
+import hudson.plugins.git.extensions.GitSCMExtension;
+import hudson.plugins.git.extensions.GitSCMExtensionDescriptor;
+import hudson.plugins.git.util.BuildData;
+import org.jenkinsci.plugins.gitclient.GitClient;
+import org.kohsuke.stapler.DataBoundConstructor;
+
+import static hudson.Util.*;
+
+/**
+ * {@link GitSCMExtension} that ignores all commits for the configured repository.
+ *
+ * @author Per Böhlin
+ */
+public class PollExclusion extends GitSCMExtension {
+
+    @DataBoundConstructor
+    public PollExclusion() {
+    }
+
+    @Override
+    public boolean requiresWorkspaceForPolling() {
+        return false;
+    }
+
+    @Override
+    public Boolean isRevExcluded(GitSCM scm, GitClient git, GitChangeSet commit, TaskListener listener, BuildData buildData) {
+        listener.getLogger().println("Ignored commit " + commit.getCommitId() + ": Repository excluded");
+        return true;
+    }
+
+    @Extension
+    public static class DescriptorImpl extends GitSCMExtensionDescriptor {
+        @Override
+        public String getDisplayName() {
+            return "Exclude the repository from polling all together";
+        }
+    }
+}

src/main/resources/hudson/plugins/git/extensions/impl/PollExclusion/help.html

@@ -0,0 +1,11 @@
+<div>
+  If set, and Jenkins is set to poll for changes, this repository will still
+  not be checked for changes. It can be useful in jobs where you want to
+  track changes and get latest commit but still don't want
+  to trigger new builds based on those changes.
+  <p/>
+  This does not require a workspace.
+  <p/>
+  If no builds exists at all, this setting will not prevent a first build from
+  being built.
+</div>

src/test/java/hudson/plugins/git/extensions/impl/PollExclusionTest.java

@@ -0,0 +1,53 @@
+package hudson.plugins.git.extensions.impl;
+
+import hudson.model.FreeStyleProject;
+import hudson.model.Result;
+import hudson.plugins.git.TestGitRepo;
+import hudson.plugins.git.extensions.GitSCMExtension;
+import hudson.plugins.git.extensions.GitSCMExtensionTest;
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+/**
+ * @author Per Böhlin
+ */
+public class PollExclusionTest extends GitSCMExtensionTest{
+
+	FreeStyleProject project;
+	TestGitRepo repo;
+
+	@Override
+	public void before() throws Exception {
+		repo = new TestGitRepo("repo", tmp.newFolder(), listener);
+		project = setupBasicProject(repo);
+	}
+
+	@Override
+	protected GitSCMExtension getExtension() {
+		return new PollExclusion();
+	}
+
+	@Test
+	public void test() throws Exception {
+
+		repo.commit("repo-init", repo.johnDoe, "repo0 initial commit");
+
+		assertTrue("Should always build when there are no builds", project.poll(listener).hasChanges());
+
+		build(project, Result.SUCCESS);
+
+		assertFalse("scm polling should never detect changes for the repository", project.poll(listener).hasChanges());
+
+		repo.commit("repo-init", repo.janeDoe, "second commit");
+
+		assertFalse("scm polling should never detect changes for the repository", project.poll(listener).hasChanges());
+
+		build(project, Result.SUCCESS);
+
+		assertFalse("scm polling should never detect changes for the repository", project.poll(listener).hasChanges());
+
+	}
+}