Clean Before Checkout

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

@@ -0,0 +1,46 @@
+package hudson.plugins.git.extensions.impl;
+
+import hudson.Extension;
+import hudson.model.AbstractBuild;
+import hudson.model.BuildListener;
+import hudson.model.TaskListener;
+import hudson.plugins.git.GitException;
+import hudson.plugins.git.GitSCM;
+import hudson.plugins.git.extensions.GitSCMExtension;
+import hudson.plugins.git.extensions.GitSCMExtensionDescriptor;
+
+import org.jenkinsci.plugins.gitclient.CloneCommand;
+import org.jenkinsci.plugins.gitclient.FetchCommand;
+import org.jenkinsci.plugins.gitclient.GitClient;
+import org.kohsuke.stapler.DataBoundConstructor;
+
+import java.io.IOException;
+
+/**
+ * git-clean before the checkout.
+ *
+ * @author David S Wang
+ */
+public class CleanBeforeCheckout extends GitSCMExtension {
+    @DataBoundConstructor
+    public CleanBeforeCheckout() {
+    }
+
+    @Override
+    public void decorateFetchCommand(GitSCM scm, GitClient git, TaskListener listener, FetchCommand cmd) throws IOException, InterruptedException, GitException {
+        listener.getLogger().println("Cleaning workspace");
+        git.clean();
+        // TODO: revisit how to hand off to SubmoduleOption
+        for (GitSCMExtension ext : scm.getExtensions()) {
+            ext.onClean(scm, git);
+        }
+    }
+
+    @Extension
+    public static class DescriptorImpl extends GitSCMExtensionDescriptor {
+        @Override
+        public String getDisplayName() {
+            return "Clean before checkout";
+        }
+    }
+}

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

@@ -0,0 +1,8 @@
+<div>
+  Clean up the workspace before every checkout by deleting all untracked files and directories,
+  including those which are specified in <tt>.gitignore</tt>.
+  It also resets all <em>tracked</em> files to their versioned state.
+  This ensures that the workspace is
+  in the same state as if you cloned and checked out in a brand-new empty directory, and ensures
+  that your build is not affected by the files generated by the previous build.
+</div>

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

@@ -4,6 +4,7 @@
 import hudson.FilePath;
 import hudson.model.*;
 import hudson.plugins.git.extensions.GitSCMExtension;
+import hudson.plugins.git.extensions.impl.CleanBeforeCheckout;
 import hudson.plugins.git.extensions.impl.DisableRemotePoll;
 import hudson.plugins.git.extensions.impl.PathRestriction;
 import hudson.plugins.git.extensions.impl.RelativeTargetDirectory;

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

@@ -8,6 +8,7 @@
 import hudson.plugins.git.browser.GithubWeb;
 import hudson.plugins.git.extensions.GitSCMExtension;
 import hudson.plugins.git.extensions.impl.AuthorInChangelog;
+import hudson.plugins.git.extensions.impl.CleanBeforeCheckout;
 import hudson.plugins.git.extensions.impl.LocalBranch;
 import hudson.plugins.git.extensions.impl.PreBuildMerge;
 import hudson.plugins.git.extensions.impl.RelativeTargetDirectory;
@@ -29,10 +30,10 @@
 import com.google.common.collect.Collections2;
 
 import hudson.util.StreamTaskListener;
+
 import org.apache.commons.io.FileUtils;
 import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.PersonIdent;
-
 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.Repository;
 import org.jenkinsci.plugins.gitclient.Git;
@@ -234,6 +235,36 @@ public void testBasicExcludedRegion() throws Exception {
         assertFalse("scm polling should not detect any more changes after build", project.poll(listener).hasChanges());
     }
 
+    public void testCleanBeforeCheckout() throws Exception {
+    	FreeStyleProject p = setupProject("master", false, null, null, "Jane Doe", null);
+        ((GitSCM)p.getScm()).getExtensions().add(new CleanBeforeCheckout());
+        final String commitFile1 = "commitFile1";
+        final String commitFile2 = "commitFile2";
+        commit(commitFile1, johnDoe, janeDoe, "Commit number 1");
+        commit(commitFile2, johnDoe, janeDoe, "Commit number 2");
+        final FreeStyleBuild firstBuild = build(p, Result.SUCCESS, commitFile1);
+        final String branch1 = "Branch1";
+        final String branch2 = "Branch2";
+        List<BranchSpec> branches = new ArrayList<BranchSpec>();
+        branches.add(new BranchSpec("master"));
+        branches.add(new BranchSpec(branch1));
+        branches.add(new BranchSpec(branch2));
+        git.branch(branch1);
+        git.checkout(branch1);
+        p.poll(listener).hasChanges();
+        assertTrue(firstBuild.getLog().contains("Cleaning"));
+        assertTrue(firstBuild.getLog().indexOf("Cleaning") > firstBuild.getLog().indexOf("Cloning")); //clean should be after clone
+        assertTrue(firstBuild.getLog().indexOf("Cleaning") < firstBuild.getLog().indexOf("Checking out")); //clean before checkout
+        assertTrue(firstBuild.getWorkspace().child(commitFile1).exists());
+        git.checkout(branch1);
+        final FreeStyleBuild secondBuild = build(p, Result.SUCCESS, commitFile2);
+        p.poll(listener).hasChanges();
+        assertTrue(secondBuild.getLog().contains("Cleaning"));
+        assertTrue(secondBuild.getLog().indexOf("Cleaning") < secondBuild.getLog().indexOf("Fetching upstream changes")); 
+        assertTrue(secondBuild.getWorkspace().child(commitFile2).exists());
+
+
+    }
     @Bug(value = 8342)
     public void testExcludedRegionMultiCommit() throws Exception {
         // Got 2 projects, each one should only build if changes in its own file