[Draft] Present HEAD commit from source branch instead of merged commit in PreBuildMerge plugin

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

@@ -1163,7 +1163,13 @@ public EnvVars getEnvironment() {
         for (GitSCMExtension ext : extensions) {
             rev = ext.decorateRevisionToBuild(this,build,git,listener,marked,rev);
         }
-        Build revToBuild = new Build(marked, rev, build.getNumber(), null);
+
+        Revision revToDisplay = rev;
+        for (GitSCMExtension ext : extensions) {
+            revToDisplay = ext.decorateRevisionToDisplay(revToDisplay, marked);
+        }
+
+        Build revToBuild = new Build(marked, rev, build.getNumber(), null, revToDisplay);
         buildData.saveBuild(revToBuild);
 
         if (buildData.getBuildsByBranchName().size() >= 100) {

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

@@ -28,6 +28,7 @@ public class UserMergeOptions extends AbstractDescribableImpl<UserMergeOptions>
     private final String mergeTarget;
     private String mergeStrategy;
     private MergeCommand.GitPluginFastForwardMode fastForwardMode;
+    private DisplayRevision displayRevision;
 
     /**
      * @deprecated use the new constructor that allows to set the fast forward mode.
@@ -40,18 +41,24 @@ public UserMergeOptions(String mergeRemote, String mergeTarget, String mergeStra
         this(mergeRemote, mergeTarget, mergeStrategy, MergeCommand.GitPluginFastForwardMode.FF);
     }
 
+    public UserMergeOptions(String mergeRemote, String mergeTarget, String mergeStrategy,
+                            MergeCommand.GitPluginFastForwardMode fastForwardMode) {
+        this(mergeRemote, mergeTarget, mergeStrategy, MergeCommand.GitPluginFastForwardMode.FF, DisplayRevision.MERGED);
+    }
+
     /**
      * @param mergeRemote remote name used for merge
      * @param mergeTarget remote branch to be merged into current branch
      * @param mergeStrategy merge strategy
      * @param fastForwardMode fast forward mode
      */
     public UserMergeOptions(String mergeRemote, String mergeTarget, String mergeStrategy,
-            MergeCommand.GitPluginFastForwardMode fastForwardMode) {
+            MergeCommand.GitPluginFastForwardMode fastForwardMode, DisplayRevision displayRevision) {
         this.mergeRemote = mergeRemote;
         this.mergeTarget = mergeTarget;
         this.mergeStrategy = mergeStrategy;
         this.fastForwardMode = fastForwardMode;
+        this.displayRevision = displayRevision;
     }
 
     @DataBoundConstructor
@@ -124,13 +131,26 @@ public void setFastForwardMode(MergeCommand.GitPluginFastForwardMode fastForward
         this.fastForwardMode = fastForwardMode;
     }
 
+    public DisplayRevision getDisplayRevision() {
+        for (DisplayRevision revision : DisplayRevision.values())
+            if (revision.equals(displayRevision))
+                return revision;
+        return DisplayRevision.MERGED;
+    }
+
+    @DataBoundSetter
+    public void setDisplayRevision(DisplayRevision displayRevision) {
+        this.displayRevision = displayRevision;
+    }
+
     @Override
     public String toString() {
         return "UserMergeOptions{" +
                 "mergeRemote='" + mergeRemote + '\'' +
                 ", mergeTarget='" + mergeTarget + '\'' +
                 ", mergeStrategy='" + getMergeStrategy().name() + '\'' +
                 ", fastForwardMode='" + getFastForwardMode().name() + '\'' +
+                ", displayRevision='" + getDisplayRevision().name() + '\'' +
                 '}';
     }
 
@@ -148,12 +168,13 @@ public boolean equals(Object o) {
         return Objects.equals(mergeRemote, that.mergeRemote)
                 && Objects.equals(mergeTarget, that.mergeTarget)
                 && Objects.equals(mergeStrategy, that.mergeStrategy)
-                && Objects.equals(fastForwardMode, that.fastForwardMode);
+                && Objects.equals(fastForwardMode, that.fastForwardMode)
+                && Objects.equals(displayRevision, that.displayRevision);
     }
 
     @Override
     public int hashCode() {
-        return Objects.hash(mergeRemote, mergeTarget, mergeStrategy, fastForwardMode);
+        return Objects.hash(mergeRemote, mergeTarget, mergeStrategy, fastForwardMode, displayRevision);
     }
 
     @Extension
@@ -175,5 +196,15 @@ public Map<String, Object> customInstantiate(Map<String, Object> arguments) {
         }
 
     }
+    public static enum DisplayRevision {
+        MERGED,
+        SOURCE_BRANCH;
+
+        private DisplayRevision() {
+        }
 
+        public String toString() {
+            return this.name().toLowerCase(Locale.ENGLISH);
+        }
+    }
 }

src/main/java/hudson/plugins/git/extensions/GitSCMExtension.java

@@ -372,4 +372,9 @@ public boolean enableMultipleRevisionDetection() {
     public GitSCMExtensionDescriptor getDescriptor() {
         return (GitSCMExtensionDescriptor) super.getDescriptor();
     }
+
+    //What should be API of this method?
+    public Revision decorateRevisionToDisplay(Revision revToDisplay, Revision marked) {
+        return revToDisplay;
+    }
 }

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

@@ -128,6 +128,12 @@ public Revision decorateRevisionToBuild(GitSCM scm, Run<?, ?> build, GitClient g
         return mergeRevision;
     }
 
+    @Override
+    //What should be API of this method?
+    public Revision decorateRevisionToDisplay(Revision revToDisplay, Revision marked) {
+        return options.getDisplayRevision() == UserMergeOptions.DisplayRevision.SOURCE_BRANCH ? marked : revToDisplay;
+    }
+
     @Override
     public void decorateMergeCommand(GitSCM scm, Run<?, ?> build, GitClient git, TaskListener listener, MergeCommand cmd) throws IOException, InterruptedException, GitException {
         if (options.getMergeStrategy() != null) {

src/main/java/hudson/plugins/git/opt/PreBuildMergeOptions.java

@@ -1,7 +1,9 @@
 package hudson.plugins.git.opt;
 
+import hudson.plugins.git.UserMergeOptions;
 import org.eclipse.jgit.transport.RemoteConfig;
 import org.jenkinsci.plugins.gitclient.MergeCommand;
+import org.kohsuke.stapler.DataBoundSetter;
 import org.kohsuke.stapler.export.Exported;
 import org.kohsuke.stapler.export.ExportedBean;
 
@@ -33,6 +35,8 @@ public class PreBuildMergeOptions implements Serializable {
 
     public MergeCommand.GitPluginFastForwardMode fastForwardMode = MergeCommand.GitPluginFastForwardMode.FF;
 
+    public UserMergeOptions.DisplayRevision displayRevision = UserMergeOptions.DisplayRevision.MERGED;
+
     public RemoteConfig getMergeRemote() {
         return mergeRemote;
     }
@@ -74,6 +78,18 @@ public void setFastForwardMode(MergeCommand.GitPluginFastForwardMode fastForward
       this.fastForwardMode = fastForwardMode;
     }
 
+    @Exported
+    public UserMergeOptions.DisplayRevision getDisplayRevision() {
+        for (UserMergeOptions.DisplayRevision revision : UserMergeOptions.DisplayRevision.values())
+            if (revision.equals(displayRevision))
+                return revision;
+        return UserMergeOptions.DisplayRevision.MERGED;
+    }
+
+    public void setDisplayRevision(UserMergeOptions.DisplayRevision displayRevision) {
+        this.displayRevision = displayRevision;
+    }
+
     @Exported
     public String getRemoteBranchName() {
         return (mergeRemote == null) ? null : mergeRemote.getName() + "/" + mergeTarget;

src/main/java/hudson/plugins/git/util/Build.java

@@ -48,6 +48,8 @@ public class Build implements Serializable, Cloneable {
      */
     public Revision revision;
 
+    public Revision displayRevision;
+
     public int      hudsonBuildNumber;
     public Result   hudsonBuildResult;
 
@@ -56,6 +58,15 @@ public class Build implements Serializable, Cloneable {
     public Build(Revision marked, Revision revision, int buildNumber, Result result) {
         this.marked = marked;
         this.revision = revision;
+        this.displayRevision = revision;
+        this.hudsonBuildNumber = buildNumber;
+        this.hudsonBuildResult = result;
+    }
+
+    public Build(Revision marked, Revision revision, int buildNumber, Result result, Revision displayRevision) {
+        this.marked = marked;
+        this.revision = revision;
+        this.displayRevision = displayRevision;
         this.hudsonBuildNumber = buildNumber;
         this.hudsonBuildResult = result;
     }
@@ -139,4 +150,9 @@ public Object readResolve() throws IOException {
             marked = revision;
         return this;
     }
+
+    @Exported
+    public Revision getDisplayRevision() {
+        return displayRevision;
+    }
 }

src/main/java/hudson/plugins/git/util/BuildData.java

@@ -253,6 +253,16 @@ public Build getLastBuildOfBranch(String branch) {
         return lastBuild==null?null:lastBuild.revision;
     }
 
+    /**
+     * Gets revision of the previous build to display.
+     * @return display revision of the last build.
+     *    May be null will be returned if nothing has been checked out (e.g. due to wrong repository or branch)
+     */
+    @Exported
+    public @CheckForNull Revision getLastBuiltDisplayRevision() {
+        return lastBuild==null?null:lastBuild.getDisplayRevision();
+    }
+
     @Exported
     public Map<String,Build> getBuildsByBranchName() {
         return buildsByBranchName;

src/main/resources/hudson/plugins/git/UserMergeOptions/config.jelly

@@ -16,4 +16,9 @@
           ${it.toString()}
       </f:enum>
   </f:entry>
+  <f:entry title="${%Revision to display}" field="displayRevision">
+        <f:enum>
+            ${it.toString()}
+        </f:enum>
+    </f:entry>
 </j:jelly>

src/main/resources/hudson/plugins/git/util/BuildData/index.jelly

@@ -8,7 +8,7 @@
 	<l:main-panel>
 	<h1>${%Git Build Data}</h1>
 
-	<strong>${%Revision}</strong>: ${it.lastBuild.SHA1.name()}
+	<strong>${%Revision}</strong>: ${it.lastBuiltDisplayRevision.sha1.name()}
 	<j:if test="${!empty(it.scmName)}"><br/><strong>${%SCM}</strong>: ${it.scmName}</j:if>
 	<j:if test="${!empty(it.remoteUrls)}">
 		<j:forEach var="remoteUrl" items="${it.remoteUrls}">
@@ -21,7 +21,7 @@
 		</j:forEach>
 	</j:if>
 	<ul>
-	<j:forEach var="branch" items="${it.lastBuild.revision.branches}">
+	<j:forEach var="branch" items="${it.lastBuiltDisplayRevision.branches}">
 	<li>${branch.name}</li>
 	</j:forEach>
 	</ul>

src/main/resources/hudson/plugins/git/util/BuildData/summary.jelly

@@ -4,7 +4,7 @@
 	xmlns:f="/lib/form" xmlns:i="jelly:fmt">
 	<t:summary icon="/plugin/git/icons/git-logo.svg">
 
-	<strong>${%Revision}</strong>: ${it.lastBuiltRevision.sha1.name()}
+	<strong>${%Revision}</strong>: ${it.lastBuiltDisplayRevision.sha1.name()}
 	<j:if test="${!empty(it.scmName)}"><br/><strong>${%SCM}</strong>: ${it.scmName}</j:if>
 	<j:if test="${!empty(it.remoteUrls)}">
 		<j:forEach var="remoteUrl" items="${it.remoteUrls}">
@@ -17,7 +17,7 @@
 		</j:forEach>
 	</j:if>
         <ul>
-        <j:forEach var="branch" items="${it.lastBuiltRevision.branches}">
+        <j:forEach var="branch" items="${it.lastBuiltDisplayRevision.branches}">
           <j:if test="${branch!=''}">
             <li>${branch.name}</li>
           </j:if>

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

@@ -11,9 +11,17 @@
 import hudson.plugins.git.extensions.GitSCMExtensionTest;
 import hudson.plugins.git.util.BuildData;
 import nl.jqno.equalsverifier.EqualsVerifier;
+import org.eclipse.jgit.lib.AnyObjectId;
+import org.eclipse.jgit.lib.ObjectId;
 import org.jenkinsci.plugins.gitclient.MergeCommand;
 import org.junit.Test;
 
+import java.io.File;
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
 import static org.junit.Assert.*;
 
 /**
@@ -26,21 +34,101 @@ public class PreBuildMergeTest extends GitSCMExtensionTest
     private TestGitRepo repo;
 
     private String MASTER_FILE = "commitFileBase";
+    private String INTEGRATION_FILE = "branchFile";
+
+    private String initCommit;
 
     public void before() throws Exception {
         repo = new TestGitRepo("repo", tmp.newFolder(), listener);
         project = setupBasicProject(repo);
         // make an initial commit to master
-        repo.commit(MASTER_FILE, repo.johnDoe, "Initial Commit");
+        initCommit = repo.commit(MASTER_FILE, repo.johnDoe, "Initial Commit");
         // create integration branch
         repo.git.branch("integration");
     }
 
     @Test
     public void testBasicPreMerge() throws Exception {
+        // already existing test
         FreeStyleBuild firstBuild = build(project, Result.SUCCESS);
     }
 
+    @Test
+    public void testDisplayMergedRevision() throws Exception {
+        // add some commits to source and target branch
+        repo.git.checkoutBranch("integration", initCommit);
+        String integrationCommit = repo.commit(INTEGRATION_FILE, repo.johnDoe, "Integration Commit");
+        repo.git.checkoutBranch("master", initCommit);
+        String masterCommit = repo.commit("Master2", repo.johnDoe, "Master2 Commit");
+
+        FreeStyleBuild firstBuild = build(project, Result.SUCCESS);
+
+        // git repository placed in build's workspace
+        TestGitRepo repoInWorkspace = getRepoInWorkspace(firstBuild);
+
+        List<ObjectId> commitsInWorkspace = getCommitsOnHead(repoInWorkspace);
+
+        ObjectId mergeCommit = commitsInWorkspace.remove(0);
+
+        // verify state of workspace fit repo
+        // is it possible to verify merge commit (checking log message?)
+        assertEquals(Arrays.asList(integrationCommit, masterCommit, initCommit),
+                commitsInWorkspace.stream().map(AnyObjectId::name).collect(Collectors.toList()));
+
+        // verify revision displayed
+        assertEquals(GitSCM.class, project.getScm().getClass());
+        GitSCM gitSCM = (GitSCM)project.getScm();
+        BuildData buildData = gitSCM.getBuildData(firstBuild);
+        Revision buildRevision = buildData.getLastBuiltDisplayRevision();
+
+        assertEquals(mergeCommit, buildRevision.getSha1());
+        assertEquals(1, buildRevision.getBranches().size());
+        assertTrue(buildRevision.containsBranchName("origin/integration"));
+    }
+
+    @Test
+    public void testDisplaySourceRevision() throws Exception {
+        // change UserMergeOption
+        GitSCM gitSCM = (GitSCM)project.getScm();
+        gitSCM.getExtensions().get(PreBuildMerge.class).getOptions().setDisplayRevision(UserMergeOptions.DisplayRevision.SOURCE_BRANCH);
+
+        // add some commits to source and target branch
+        repo.git.checkoutBranch("integration", initCommit);
+        String integrationCommit = repo.commit(INTEGRATION_FILE, repo.johnDoe, "Integration Commit");
+        repo.git.checkoutBranch("master", initCommit);
+        String masterCommit = repo.commit("Master2", repo.johnDoe, "Master2 Commit");
+
+        FreeStyleBuild firstBuild = build(project, Result.SUCCESS);
+
+        // git repository placed in build's workspace
+        TestGitRepo repoInWorkspace = getRepoInWorkspace(firstBuild);
+        List<ObjectId> commitsInWorkspace = getCommitsOnHead(repoInWorkspace);
+
+        ObjectId mergeCommit = commitsInWorkspace.remove(0);
+
+        // verify state of workspace fit repo
+        // is it possible to verify merge commit (checking log message?)
+        assertEquals(Arrays.asList(integrationCommit, masterCommit, initCommit),
+                commitsInWorkspace.stream().map(AnyObjectId::name).collect(Collectors.toList()));
+        assertEquals(GitSCM.class, project.getScm().getClass());
+
+        // verify revision displayed
+        BuildData buildData = gitSCM.getBuildData(firstBuild);
+        Revision buildRevision = buildData.getLastBuiltDisplayRevision();
+
+        assertEquals(masterCommit, buildRevision.getSha1().name());
+        assertEquals(1, buildRevision.getBranches().size());
+        assertTrue(buildRevision.containsBranchName("origin/master"));
+    }
+
+    private List<ObjectId> getCommitsOnHead(TestGitRepo repoInWorkspace) throws InterruptedException {
+        return repoInWorkspace.git.revList("HEAD");
+    }
+
+    private TestGitRepo getRepoInWorkspace(FreeStyleBuild firstBuild) throws IOException, InterruptedException {
+        return new TestGitRepo("workspace", new File(firstBuild.getWorkspace().toString()), listener);
+    }
+
     @Test
     public void testFailedMerge() throws Exception {
         FreeStyleBuild firstBuild = build(project, Result.SUCCESS);