Fix DirCacheCheckout to return CheckoutConflictException

Problem occurs when the checkout wants to create a file 'd/f' but
the workingtree contains a dirty file 'd'. In order to create d/f the
file 'd' would have to be deleted and since the file is dirty that
content would be lost. This should lead to a CheckoutConflictException
for d/f when failOnConflict was set to true.

This fix also changes jgit checkout semantics to be more like native
gits checkout semantics. If during a checkout jgit wants to delete a
folder but finds that the working tree contains a dirty file at this
path then JGit will now throw an exception instead of silently keeping
the dirty file. Like in this example:

	git init
	touch b
	git add b
	git commit -m addB
	mkdir a
	touch a/c
	git add a/c
	git commit -m addAC
	rm -fr a
	touch a
	git checkout HEAD~

Change-Id: I9089123179e09dd565285d50b0caa308d290cccd
Signed-off-by: Rüdiger Herrmann <ruediger.herrmann@gmx.de>
Also-by: Rüdiger Herrmann <ruediger.herrmann@gmx.de>

1 files changed, 28 insertions, 4 deletions

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/dircache/DirCacheCheckout.java b/org.eclipse.jgit/src/org/eclipse/jgit/dircache/DirCacheCheckout.java
index 12ceb74abb..ab61c59378 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/dircache/DirCacheCheckout.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/dircache/DirCacheCheckout.java
@@ -718,10 +718,23 @@ public class DirCacheCheckout {
 			return;
 		}
 
-		// if we have no file at all then there is nothing to do
-		if ((ffMask & 0x222) == 0
-				&& (f == null || FileMode.TREE.equals(f.getEntryFileMode())))
-			return;
+		if ((ffMask & 0x222) == 0) {
+			// HEAD, MERGE and index don't contain a file (e.g. all contain a
+			// folder)
+			if (f == null || FileMode.TREE.equals(f.getEntryFileMode())) {
+				// the workingtree entry doesn't exist or also contains a folder
+				// -> no problem
+				return;
+			} else {
+				// the workingtree entry exists and is not a folder
+				if (!idEqual(h, m)) {
+					// Because HEAD and MERGE differ we will try to update the
+					// workingtree with a folder -> return a conflict
+					conflict(name, null, null, null);
+				}
+				return;
+			}
+		}
 
 		if ((ffMask == 0x00F) && f != null && FileMode.TREE.equals(f.getEntryFileMode())) {
 			// File/Directory conflict case #20
@@ -1004,6 +1017,17 @@ public class DirCacheCheckout {
 		}
 	}
 
+	private static boolean idEqual(AbstractTreeIterator a,
+			AbstractTreeIterator b) {
+		if (a == b) {
+			return true;
+		}
+		if (a == null || b == null) {
+			return false;
+		}
+		return a.getEntryObjectId().equals(b.getEntryObjectId());
+	}
+
 	/**
 	 * A conflict is detected - add the three different stages to the index
 	 * @param path the path of the conflicting entry