Fix rebase > continue when nothing left to commit.refs/changes/59/4959/7

If after resolving all conflicts nothing is left to commit, return
an according result, so that downstreams (EGit, ...) can behave like
cgit, and display a nice message informing the user.

Currently, EGit displays a "HEAD advanced fast forward" message, which
is absolutely not helpful at all.

This is the basic API revamping required to get that state communicated
to the outside world (EGit).

Bug: 336812
Change-Id: If2665005cf54a5b51c0fe80bad019fa42b0205af

3 files changed, 82 insertions, 3 deletions

diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/api/RebaseCommandTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/api/RebaseCommandTest.java
index 672f4d8..648ef6f 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/api/RebaseCommandTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/api/RebaseCommandTest.java
@@ -503,6 +503,55 @@ public class RebaseCommandTest extends RepositoryTestCase {
 	}
 
 	@Test
+	public void testStopOnConflictAndContinueWithNoDeltaToMaster()
+			throws Exception {
+		// create file1 on master
+		RevCommit firstInMaster = writeFileAndCommit(FILE1, "Add file1", "1",
+				"2", "3");
+		// change in master
+		writeFileAndCommit(FILE1, "change file1 in master", "1master", "2", "3");
+
+		checkFile(FILE1, "1master", "2", "3");
+		// create a topic branch based on the first commit
+		createBranch(firstInMaster, "refs/heads/topic");
+		checkoutBranch("refs/heads/topic");
+		// we have the old content again
+		checkFile(FILE1, "1", "2", "3");
+
+		// change first line (conflicting)
+		writeFileAndCommit(FILE1,
+				"change file1 in topic\n\nThis is conflicting", "1topic", "2",
+				"3", "4topic");
+
+		RebaseResult res = git.rebase().setUpstream("refs/heads/master").call();
+		assertEquals(Status.STOPPED, res.getStatus());
+
+		// continue should throw a meaningful exception
+		try {
+			res = git.rebase().setOperation(Operation.CONTINUE).call();
+			fail("Expected Exception not thrown");
+		} catch (UnmergedPathsException e) {
+			// expected
+		}
+
+		// merge the file; the second topic commit should go through
+		writeFileAndAdd(FILE1, "1master", "2", "3");
+
+		res = git.rebase().setOperation(Operation.CONTINUE).call();
+		assertNotNull(res);
+		assertEquals(Status.NOTHING_TO_COMMIT, res.getStatus());
+		assertEquals(RepositoryState.REBASING_INTERACTIVE,
+				db.getRepositoryState());
+
+		git.rebase().setOperation(Operation.SKIP).call();
+
+		ObjectId headId = db.resolve(Constants.HEAD);
+		RevWalk rw = new RevWalk(db);
+		RevCommit rc = rw.parseCommit(headId);
+		assertEquals("change file1 in master", rc.getFullMessage());
+	}
+
+	@Test
 	public void testStopOnConflictAndFailContinueIfFileIsDirty()
 			throws Exception {
 		// create file1 on master
@@ -775,8 +824,15 @@ public class RebaseCommandTest extends RepositoryTestCase {
 
 		res = git.rebase().setOperation(Operation.CONTINUE).call();
 		assertNotNull(res);
-		assertEquals(Status.OK, res.getStatus());
-		assertEquals(RepositoryState.SAFE, db.getRepositoryState());
+
+		// nothing to commit. this leaves the repo state in rebase, so that the
+		// user can decide what to do. if he accidentally committed, reset soft,
+		// and continue, if he really has nothing to commit, skip.
+		assertEquals(Status.NOTHING_TO_COMMIT, res.getStatus());
+		assertEquals(RepositoryState.REBASING_INTERACTIVE,
+				db.getRepositoryState());
+
+		git.rebase().setOperation(Operation.SKIP).call();
 
 		ObjectId headId = db.resolve(Constants.HEAD);
 		RevWalk rw = new RevWalk(db);
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/api/RebaseCommand.java b/org.eclipse.jgit/src/org/eclipse/jgit/api/RebaseCommand.java
index ae73cac..936f5ca 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/api/RebaseCommand.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/api/RebaseCommand.java
@@ -220,9 +220,19 @@ public class RebaseCommand extends GitCommand<RebaseResult> {
 			if (monitor.isCancelled())
 				return abort(RebaseResult.ABORTED_RESULT);
 
-			if (operation == Operation.CONTINUE)
+			if (operation == Operation.CONTINUE) {
 				newHead = continueRebase();
 
+				if (newHead == null) {
+					// continueRebase() returns null only if no commit was
+					// neccessary. This means that no changes where left over
+					// after resolving all conflicts. In this case, cgit stops
+					// and displays a nice message to the user, telling him to
+					// either do changes or skip the commit instead of continue.
+					return RebaseResult.NOTHING_TO_COMMIT_RESULT;
+				}
+			}
+
 			if (operation == Operation.SKIP)
 				newHead = checkoutCurrentHead();
 
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/api/RebaseResult.java b/org.eclipse.jgit/src/org/eclipse/jgit/api/RebaseResult.java
index e389d99..4739f16 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/api/RebaseResult.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/api/RebaseResult.java
@@ -109,6 +109,16 @@ public class RebaseResult {
 			public boolean isSuccessful() {
 				return true;
 			}
+		},
+
+		/**
+		 * Continue with nothing left to commit (possibly want skip).
+		 */
+		NOTHING_TO_COMMIT {
+			@Override
+			public boolean isSuccessful() {
+				return false;
+			}
 		};
 
 		/**
@@ -127,6 +137,9 @@ public class RebaseResult {
 	static final RebaseResult FAST_FORWARD_RESULT = new RebaseResult(
 			Status.FAST_FORWARD);
 
+	static final RebaseResult NOTHING_TO_COMMIT_RESULT = new RebaseResult(
+			Status.NOTHING_TO_COMMIT);
+
 	private final Status status;
 
 	private final RevCommit currentCommit;