Allow to resolve a conflict by checking out a file

DirCacheEditor unconditionally applied a PathEdit to all stages in the
index. This gives wrong results if one wants to check out a file from
some commit to resolve a conflict: JGit would update the working tree
file multiple times (once per stage), and set all stages to point to
the checked-out blob.

C git replaces the stages by the entry for the checked-out file.

To support this, add a DirCacheEntry.setStage() method so that
CheckoutCommand can force the stage to zero. In DirCacheEditor, keep
only the zero stage if the PathEdit re-set the stage.

Bug: 568038
Change-Id: Ic7c635bb5aaa06ffaaeed50bc5e45702c56fc6d1
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

3 files changed, 79 insertions, 2 deletions

diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/api/PathCheckoutCommandTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/api/PathCheckoutCommandTest.java
index e0a1c1d61b..f52b715d39 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/api/PathCheckoutCommandTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/api/PathCheckoutCommandTest.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2011, Kevin Sawicki <kevin@github.com> and others
+ * Copyright (C) 2011, 2020 Kevin Sawicki <kevin@github.com> and others
  *
  * This program and the accompanying materials are made available under the
  * terms of the Eclipse Distribution License v. 1.0 which is available at
@@ -24,6 +24,7 @@ import org.eclipse.jgit.dircache.DirCacheEntry;
 import org.eclipse.jgit.errors.NoWorkTreeException;
 import org.eclipse.jgit.junit.RepositoryTestCase;
 import org.eclipse.jgit.lib.ConfigConstants;
+import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.ObjectReader;
 import org.eclipse.jgit.lib.RepositoryState;
 import org.eclipse.jgit.lib.StoredConfig;
@@ -310,6 +311,16 @@ public class PathCheckoutCommandTest extends RepositoryTestCase {
 	}
 
 	@Test
+	public void testCheckoutFileWithConflict() throws Exception {
+		setupConflictingState();
+		assertEquals('[' + FILE1 + ']',
+				git.status().call().getConflicting().toString());
+		git.checkout().setStartPoint(Constants.HEAD).addPath(FILE1).call();
+		assertEquals("3", read(FILE1));
+		assertTrue(git.status().call().isClean());
+	}
+
+	@Test
 	public void testCheckoutOursWhenNoBase() throws Exception {
 		String file = "added.txt";
 
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/dircache/DirCacheEntryTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/dircache/DirCacheEntryTest.java
index 5477f565f4..8e84dfa318 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/dircache/DirCacheEntryTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/dircache/DirCacheEntryTest.java
@@ -242,6 +242,46 @@ public class DirCacheEntryTest {
 	}
 
 	@Test
+	public void testSetStage() {
+		DirCacheEntry e = new DirCacheEntry("some/path", DirCacheEntry.STAGE_1);
+		e.setAssumeValid(true);
+		e.setCreationTime(2L);
+		e.setFileMode(FileMode.EXECUTABLE_FILE);
+		e.setLastModified(EPOCH.plusMillis(3L));
+		e.setLength(100L);
+		e.setObjectId(ObjectId
+				.fromString("0123456789012345678901234567890123456789"));
+		e.setUpdateNeeded(true);
+		e.setStage(DirCacheEntry.STAGE_2);
+
+		assertTrue(e.isAssumeValid());
+		assertEquals(2L, e.getCreationTime());
+		assertEquals(
+				ObjectId.fromString("0123456789012345678901234567890123456789"),
+				e.getObjectId());
+		assertEquals(FileMode.EXECUTABLE_FILE, e.getFileMode());
+		assertEquals(EPOCH.plusMillis(3L), e.getLastModifiedInstant());
+		assertEquals(100L, e.getLength());
+		assertEquals(DirCacheEntry.STAGE_2, e.getStage());
+		assertTrue(e.isUpdateNeeded());
+		assertEquals("some/path", e.getPathString());
+
+		e.setStage(DirCacheEntry.STAGE_0);
+
+		assertTrue(e.isAssumeValid());
+		assertEquals(2L, e.getCreationTime());
+		assertEquals(
+				ObjectId.fromString("0123456789012345678901234567890123456789"),
+				e.getObjectId());
+		assertEquals(FileMode.EXECUTABLE_FILE, e.getFileMode());
+		assertEquals(EPOCH.plusMillis(3L), e.getLastModifiedInstant());
+		assertEquals(100L, e.getLength());
+		assertEquals(DirCacheEntry.STAGE_0, e.getStage());
+		assertTrue(e.isUpdateNeeded());
+		assertEquals("some/path", e.getPathString());
+	}
+
+	@Test
 	public void testCopyMetaDataWithStage() {
 		copyMetaDataHelper(false);
 	}
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/dircache/DirCachePathEditTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/dircache/DirCachePathEditTest.java
index 39a1f01803..5778d28d6f 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/dircache/DirCachePathEditTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/dircache/DirCachePathEditTest.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2011, Robin Rosenberg and others
+ * Copyright (C) 2011, 2020 Robin Rosenberg and others
  *
  * This program and the accompanying materials are made available under the
  * terms of the Eclipse Distribution License v. 1.0 which is available at
@@ -124,6 +124,32 @@ public class DirCachePathEditTest {
 	}
 
 	@Test
+	public void testPathEditWithStagesAndReset() throws Exception {
+		DirCache dc = DirCache.newInCore();
+		DirCacheBuilder builder = new DirCacheBuilder(dc, 3);
+		builder.add(createEntry("a", DirCacheEntry.STAGE_1));
+		builder.add(createEntry("a", DirCacheEntry.STAGE_2));
+		builder.add(createEntry("a", DirCacheEntry.STAGE_3));
+		builder.finish();
+
+		DirCacheEditor editor = dc.editor();
+		PathEdit edit = new PathEdit("a") {
+
+			@Override
+			public void apply(DirCacheEntry ent) {
+				ent.setStage(DirCacheEntry.STAGE_0);
+			}
+		};
+		editor.add(edit);
+		editor.finish();
+
+		assertEquals(1, dc.getEntryCount());
+		DirCacheEntry entry = dc.getEntry(0);
+		assertEquals("a", entry.getPathString());
+		assertEquals(DirCacheEntry.STAGE_0, entry.getStage());
+	}
+
+	@Test
 	public void testFileReplacesTree() throws Exception {
 		DirCache dc = DirCache.newInCore();
 		DirCacheEditor editor = dc.editor();