Fix applying stash on other commit

Applying a stash on another commit failed because the merge base for the
cherry-pick of the stashed index state was not corectly set.

Bug: 422684
Change-Id: I9355352b2b9a7abefa3248ca3c17a9301177d0d6
Signed-off-by: Stefan Lay <stefan.lay@sap.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/api/StashApplyCommandTest.java

@@ -408,6 +408,93 @@ public class StashApplyCommandTest extends RepositoryTestCase {
 				read(PATH));
 	}
 
+	@Test
+	public void stashedApplyOnOtherBranch() throws Exception {
+		writeTrashFile(PATH, "content\nmore content\n");
+		git.add().addFilepattern(PATH).call();
+		git.commit().setMessage("more content").call();
+		String path2 = "file2.txt";
+		File file2 = writeTrashFile(path2, "content\nmore content\n");
+		git.add().addFilepattern(PATH).call();
+		git.add().addFilepattern(path2).call();
+		git.commit().setMessage("even content").call();
+
+		String otherBranch = "otherBranch";
+		git.branchCreate().setName(otherBranch).call();
+
+		writeTrashFile(PATH, "master content");
+		git.add().addFilepattern(PATH).call();
+		git.commit().setMessage("even content").call();
+
+		git.checkout().setName(otherBranch).call();
+
+		writeTrashFile(PATH, "otherBranch content");
+		git.add().addFilepattern(PATH).call();
+		git.commit().setMessage("even more content").call();
+
+		writeTrashFile(path2, "content\nstashed change\nmore content\n");
+
+		RevCommit stashed = git.stashCreate().call();
+
+		assertNotNull(stashed);
+		assertEquals("content\nmore content\n", read(file2));
+		assertEquals("otherBranch content",
+				read(committedFile));
+		assertTrue(git.status().call().isClean());
+
+		git.checkout().setName("master").call();
+		git.stashApply().call();
+		assertEquals("content\nstashed change\nmore content\n", read(file2));
+		assertEquals("master content",
+				read(committedFile));
+	}
+
+	@Test
+	public void stashedApplyOnOtherBranchWithStagedChange() throws Exception {
+		writeTrashFile(PATH, "content\nmore content\n");
+		git.add().addFilepattern(PATH).call();
+		git.commit().setMessage("more content").call();
+		String path2 = "file2.txt";
+		File file2 = writeTrashFile(path2, "content\nmore content\n");
+		git.add().addFilepattern(PATH).call();
+		git.add().addFilepattern(path2).call();
+		git.commit().setMessage("even content").call();
+
+		String otherBranch = "otherBranch";
+		git.branchCreate().setName(otherBranch).call();
+
+		writeTrashFile(PATH, "master content");
+		git.add().addFilepattern(PATH).call();
+		git.commit().setMessage("even content").call();
+
+		git.checkout().setName(otherBranch).call();
+
+		writeTrashFile(PATH, "otherBranch content");
+		git.add().addFilepattern(PATH).call();
+		git.commit().setMessage("even more content").call();
+
+		writeTrashFile(path2,
+				"content\nstashed change in index\nmore content\n");
+		git.add().addFilepattern(path2).call();
+		writeTrashFile(path2, "content\nstashed change\nmore content\n");
+
+		RevCommit stashed = git.stashCreate().call();
+
+		assertNotNull(stashed);
+		assertEquals("content\nmore content\n", read(file2));
+		assertEquals("otherBranch content", read(committedFile));
+		assertTrue(git.status().call().isClean());
+
+		git.checkout().setName("master").call();
+		git.stashApply().call();
+		assertEquals("content\nstashed change\nmore content\n", read(file2));
+		assertEquals(
+				"[file.txt, mode:100644, content:master content]"
+						+ "[file2.txt, mode:100644, content:content\nstashed change in index\nmore content\n]",
+				indexState(CONTENT));
+		assertEquals("master content", read(committedFile));
+	}
+
 	@Test
 	public void workingDirectoryContentMerge() throws Exception {
 		writeTrashFile(PATH, "content\nmore content\n");

org.eclipse.jgit/src/org/eclipse/jgit/api/StashApplyCommand.java

@@ -185,6 +185,7 @@ public class StashApplyCommand extends GitCommand<ObjectId> {
 							.newMerger(repo, true);
 					ixMerger.setCommitNames(new String[] { "stashed HEAD",
 							"HEAD", "stashed index" });
+					ixMerger.setBase(stashHeadCommit);
 					boolean ok = ixMerger.merge(headCommit, stashIndexCommit);
 					if (ok) {
 						resetIndex(revWalk