Allow cherry-picking merge commits

If the commit to be cherry-picked is a merge commit, ask the user to
choose the parent commit to define the changes to be applied. Then
pass on the chosen parent (index) to JGit's CherryPickCommand.

Bug: 531953
Change-Id: I1d9eb551d6db5ad39a4a5d96a0196cfd3f4f4e95
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

4 files changed, 90 insertions, 16 deletions

diff --git a/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/UIText.java b/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/UIText.java
index f756b82360..57404310e8 100644
--- a/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/UIText.java
+++ b/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/UIText.java
@@ -1220,6 +1220,9 @@ public class UIText extends NLS {
 	public static String CherryPickHandler_CherryPickFailedMessage;
 
 	/** */
+	public static String CherryPickHandler_CherryPickMergeMessage;
+
+	/** */
 	public static String CherryPickHandler_CouldNotDeleteFile;
 
 	/** */
@@ -5130,6 +5133,9 @@ public class UIText extends NLS {
 	public static String CommitSelectDialog_WindowTitle;
 
 	/** */
+	public static String CommitSelectDialog_ChooseParentTitle;
+
+	/** */
 	public static String CommitSelectionDialog_BuildingCommitListMessage;
 
 	/** */
diff --git a/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/commit/command/CherryPickHandler.java b/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/commit/command/CherryPickHandler.java
index 4ff37efee8..0b372c4551 100644
--- a/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/commit/command/CherryPickHandler.java
+++ b/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/commit/command/CherryPickHandler.java
@@ -38,6 +38,7 @@ import org.eclipse.egit.ui.internal.UIRepositoryUtils;
 import org.eclipse.egit.ui.internal.UIText;
 import org.eclipse.egit.ui.internal.branch.LaunchFinder;
 import org.eclipse.egit.ui.internal.commit.RepositoryCommit;
+import org.eclipse.egit.ui.internal.dialogs.CommitSelectDialog;
 import org.eclipse.egit.ui.internal.handler.SelectionHandler;
 import org.eclipse.jface.dialogs.IDialogConstants;
 import org.eclipse.jface.dialogs.MessageDialog;
@@ -74,18 +75,46 @@ public class CherryPickHandler extends SelectionHandler {
 	@Override
 	public Object execute(ExecutionEvent event) throws ExecutionException {
 		RevCommit commit = getSelectedItem(RevCommit.class, event);
-		if (commit == null)
+		if (commit == null) {
 			return null;
+		}
 		Repository repo = getSelectedItem(Repository.class, event);
-		if (repo == null)
+		if (repo == null) {
 			return null;
-		final Shell parent = getPart(event).getSite().getShell();
+		}
+		final Shell shell = getPart(event).getSite().getShell();
 
-		if (!confirmCherryPick(parent, repo, commit))
+		int parentIndex = -1;
+		if (commit.getParentCount() > 1) {
+			// Merge commit: select parent
+			List<RevCommit> parents = new ArrayList<>();
+			String branch = null;
+			try {
+				for (RevCommit parent : commit.getParents()) {
+					parents.add(repo.parseCommit(parent));
+				}
+				branch = repo.getBranch();
+			} catch (Exception e) {
+				Activator.handleError(e.getLocalizedMessage(), e, true);
+				return null;
+			}
+			CommitSelectDialog selectCommit = new CommitSelectDialog(shell,
+					parents, getLaunchMessage(repo));
+			selectCommit.create();
+			selectCommit.setTitle(UIText.CommitSelectDialog_ChooseParentTitle);
+			selectCommit.setMessage(MessageFormat.format(
+					UIText.CherryPickHandler_CherryPickMergeMessage,
+					commit.abbreviate(7).name(), branch));
+			if (selectCommit.open() != Window.OK) {
+				return null;
+			}
+			parentIndex = parents.indexOf(selectCommit.getSelectedCommit());
+		} else if (!confirmCherryPick(shell, repo, commit)) {
 			return null;
+		}
 
 		try {
-			if (!UIRepositoryUtils.handleUncommittedFiles(repo, parent))
+			if (!UIRepositoryUtils.handleUncommittedFiles(repo, shell))
 				return null;
 		} catch (GitAPIException e) {
 			Activator.logError(e.getMessage(), e);
@@ -93,6 +122,8 @@ public class CherryPickHandler extends SelectionHandler {
 		}
 
 		final CherryPickOperation op = new CherryPickOperation(repo, commit);
+		op.setMainlineIndex(parentIndex);
+
 		Job job = new Job(MessageFormat.format(
 				UIText.CherryPickHandler_JobName, Integer.valueOf(1))) {
 			@Override
@@ -102,13 +133,15 @@ public class CherryPickHandler extends SelectionHandler {
 					CherryPickResult cherryPickResult = op.getResult();
 					RevCommit newHead = cherryPickResult.getNewHead();
 					if (newHead != null
-							&& cherryPickResult.getCherryPickedRefs().isEmpty())
-						showNotPerformedDialog(parent);
+							&& cherryPickResult.getCherryPickedRefs()
+									.isEmpty()) {
+						showNotPerformedDialog(shell);
+					}
 					if (newHead == null) {
 						CherryPickStatus status = cherryPickResult.getStatus();
 						switch (status) {
 						case CONFLICTING:
-							showConflictDialog(parent);
+							showConflictDialog(shell);
 							break;
 						case FAILED:
 							showFailure(cherryPickResult);
@@ -126,8 +159,9 @@ public class CherryPickHandler extends SelectionHandler {
 
 			@Override
 			public boolean belongsTo(Object family) {
-				if (JobFamilies.CHERRY_PICK.equals(family))
+				if (JobFamilies.CHERRY_PICK.equals(family)) {
 					return true;
+				}
 				return super.belongsTo(family);
 			}
 		};
@@ -137,6 +171,17 @@ public class CherryPickHandler extends SelectionHandler {
 		return null;
 	}
 
+	private String getLaunchMessage(Repository repository) {
+		ILaunchConfiguration launch = LaunchFinder
+				.getRunningLaunchConfiguration(
+						Collections.singleton(repository), null);
+		if (launch != null) {
+			return MessageFormat.format(
+					UIText.LaunchFinder_RunningLaunchMessage, launch.getName());
+		}
+		return null;
+	}
+
 	private boolean confirmCherryPick(final Shell shell,
 			final Repository repository, final RevCommit commit)
 			throws ExecutionException {
@@ -151,12 +196,9 @@ public class CherryPickHandler extends SelectionHandler {
 					"Exception obtaining current repository branch", e); //$NON-NLS-1$
 		}
 
-		ILaunchConfiguration launch = LaunchFinder
-				.getRunningLaunchConfiguration(
-						Collections.singleton(repository), null);
-		if (launch != null) {
-			message += "\n\n" + MessageFormat.format( //$NON-NLS-1$
-					UIText.LaunchFinder_RunningLaunchMessage, launch.getName());
+		String launchMessage = getLaunchMessage(repository);
+		if (launchMessage != null) {
+			message += "\n\n" + launchMessage; //$NON-NLS-1$
 		}
 		final String question = message;
 		shell.getDisplay().syncExec(new Runnable() {
diff --git a/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/dialogs/CommitSelectDialog.java b/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/dialogs/CommitSelectDialog.java
index bed04c36e3..ab122d1ae0 100644
--- a/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/dialogs/CommitSelectDialog.java
+++ b/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/dialogs/CommitSelectDialog.java
@@ -29,6 +29,7 @@ import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.swt.SWT;
 import org.eclipse.swt.widgets.Composite;
 import org.eclipse.swt.widgets.Control;
+import org.eclipse.swt.widgets.Label;
 import org.eclipse.swt.widgets.Shell;
 import org.eclipse.swt.widgets.Table;
 import org.eclipse.swt.widgets.TableColumn;
@@ -40,6 +41,8 @@ import org.eclipse.swt.widgets.TableColumn;
 public class CommitSelectDialog extends TitleAreaDialog {
 	private final List<RevCommit> commits = new ArrayList<>();
 
+	private final String message;
+
 	private RevCommit selected;
 
 	/**
@@ -47,10 +50,26 @@ public class CommitSelectDialog extends TitleAreaDialog {
 	 * @param commits
 	 **/
 	public CommitSelectDialog(Shell parent, List<RevCommit> commits) {
+		this(parent, commits, null);
+	}
+
+	/**
+	 * Creates a new {@link CommitSelectDialog} instance.
+	 *
+	 * @param parent
+	 *            {@link Shell} to use as parent for the dialog
+	 * @param commits
+	 *            to display
+	 * @param message
+	 *            to display
+	 */
+	public CommitSelectDialog(Shell parent, List<RevCommit> commits,
+			String message) {
 		super(parent);
 		setShellStyle(getShellStyle() | SWT.SHELL_TRIM);
 		this.commits.addAll(commits);
 		setHelpAvailable(false);
+		this.message = message;
 	}
 
 	/**
@@ -111,6 +130,11 @@ public class CommitSelectDialog extends TitleAreaDialog {
 				okPressed();
 			}
 		});
+		if (message != null) {
+			Label label = new Label(main, SWT.LEFT | SWT.WRAP);
+			GridDataFactory.fillDefaults().grab(true, false).applyTo(label);
+			label.setText(message);
+		}
 		return main;
 	}
 
diff --git a/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/uitext.properties b/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/uitext.properties
index 1c83f67f1a..6c6f3a20cc 100644
--- a/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/uitext.properties
+++ b/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/uitext.properties
@@ -291,6 +291,7 @@ CherryPickHandler_NoCherryPickPerformedTitle=No cherry-pick performed
 CherryPickHandler_CherryPickConflictsMessage=Cherry-pick could not be completed automatically because of conflicts. Please resolve and commit.
 CherryPickHandler_CherryPickConflictsTitle=Cherry-Pick Conflicts
 CherryPickHandler_CherryPickFailedMessage=Cherry-pick failed
+CherryPickHandler_CherryPickMergeMessage=Cherry-picking merge commit {0} onto branch {1}. Select the parent commit to define which changes are to be cherry-picked.
 CherryPickHandler_CouldNotDeleteFile=Could not delete file
 CherryPickHandler_ErrorMsgTemplate={0} {1}
 CherryPickHandler_IndexDirty=Index is dirty
@@ -1617,10 +1618,11 @@ CommitSearchResult_LabelSingle=''{0}'' - 1 commit match
 CommitSelectDialog_AuthoColumn=Author
 CommitSelectDialog_DateColumn=Date
 CommitSelectDialog_IdColumn=Id
-CommitSelectDialog_Message=Please select a Commit
+CommitSelectDialog_Message=Please select a commit
 CommitSelectDialog_MessageColumn=Message
 CommitSelectDialog_Title=Commit Selection
 CommitSelectDialog_WindowTitle=Commit Selection
+CommitSelectDialog_ChooseParentTitle=Choose Parent Commit
 CommitSelectionDialog_BuildingCommitListMessage=Building commit list
 CommitSelectionDialog_DialogMessage=Please select a commit from the list
 CommitSelectionDialog_DialogTitle={0} commits in repository {1}