Fix "jgit checkout -f" to overwrite dirty worktree files

CheckoutCommand had a setForce() method. But this didn't correspond
to native git's 'git checkout -f' option. Deprecate the old setForce()
method and move its implementation to a new method setForceRefUpdate()
and use it to implement the -B option in the CLI class Checkout.

Add a setForced() method and use it to fix the associated '-f' option of
the CLI Checkout class to behave like native git's 'git checkout -f'
which overwrites dirty worktree files during checkout.

This is still not fully matching native git's behavior: updating
additionally dirty index entries is not done yet.

Bug: 530771
Change-Id: I776b78eb623b6ea0aca42f681788f2e4b1667f15
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

2 files changed, 86 insertions, 14 deletions

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/api/CheckoutCommand.java b/org.eclipse.jgit/src/org/eclipse/jgit/api/CheckoutCommand.java
index 455a2e665f..e05f6f1bd6 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/api/CheckoutCommand.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/api/CheckoutCommand.java
@@ -162,7 +162,9 @@ public class CheckoutCommand extends GitCommand<Ref> {
 
 	private String name;
 
-	private boolean force = false;
+	private boolean forceRefUpdate = false;
+
+	private boolean forced = false;
 
 	private boolean createBranch = false;
 
@@ -269,7 +271,11 @@ public class CheckoutCommand extends GitCommand<Ref> {
 			try {
 				dco = new DirCacheCheckout(repo, headTree, dc,
 						newCommit.getTree());
-				dco.setFailOnConflict(!force);
+				dco.setFailOnConflict(true);
+				dco.setForce(forced);
+				if (forced) {
+					dco.setFailOnConflict(false);
+				}
 				dco.setProgressMonitor(monitor);
 				try {
 					dco.checkout();
@@ -286,7 +292,7 @@ public class CheckoutCommand extends GitCommand<Ref> {
 				ref = null;
 			String toName = Repository.shortenRefName(name);
 			RefUpdate refUpdate = repo.updateRef(Constants.HEAD, ref == null);
-			refUpdate.setForceUpdate(force);
+			refUpdate.setForceUpdate(forceRefUpdate);
 			refUpdate.setRefLogMessage(refLogMessage + " to " + toName, false); //$NON-NLS-1$
 			Result updateResult;
 			if (ref != null)
@@ -666,10 +672,54 @@ public class CheckoutCommand extends GitCommand<Ref> {
 	 *            set to a new start-point; if false, the existing branch will
 	 *            not be changed
 	 * @return this instance
+	 * @deprecated this method was badly named comparing its semantics to native
+	 *             git's checkout --force option, use
+	 *             {@link #setForceRefUpdate(boolean)} instead
 	 */
+	@Deprecated
 	public CheckoutCommand setForce(boolean force) {
+		return setForceRefUpdate(force);
+	}
+
+	/**
+	 * Specify to force the ref update in case of a branch switch.
+	 *
+	 * In releases prior to 5.2 this method was called setForce() but this name
+	 * was misunderstood to implement native git's --force option, which is not
+	 * true.
+	 *
+	 * @param forceRefUpdate
+	 *            if <code>true</code> and the branch with the given name
+	 *            already exists, the start-point of an existing branch will be
+	 *            set to a new start-point; if false, the existing branch will
+	 *            not be changed
+	 * @return this instance
+	 * @since 5.3
+	 */
+	public CheckoutCommand setForceRefUpdate(boolean forceRefUpdate) {
+		checkCallable();
+		this.forceRefUpdate = forceRefUpdate;
+		return this;
+	}
+
+	/**
+	 * Allow a checkout even if the workingtree or index differs from HEAD. This
+	 * matches native git's '--force' option.
+	 *
+	 * JGit releases before 5.2 had a method <code>setForce()</code> offering
+	 * semantics different from this new <code>setForced()</code>. This old
+	 * semantic can now be found in {@link #setForceRefUpdate(boolean)}
+	 *
+	 * @param forced
+	 *            if set to <code>true</code> then allow the checkout even if
+	 *            workingtree or index doesn't match HEAD. Overwrite workingtree
+	 *            files and index content with the new content in this case.
+	 * @return this instance
+	 * @since 5.3
+	 */
+	public CheckoutCommand setForced(boolean forced) {
 		checkCallable();
-		this.force = force;
+		this.forced = forced;
 		return this;
 	}
 
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 ce7485bf1f..307fd3f310 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/dircache/DirCacheCheckout.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/dircache/DirCacheCheckout.java
@@ -155,6 +155,8 @@ public class DirCacheCheckout {
 
 	private boolean failOnConflict = true;
 
+	private boolean force = false;
+
 	private ArrayList<String> toBeDeleted = new ArrayList<>();
 
 	private boolean initialCheckout;
@@ -427,11 +429,11 @@ public class DirCacheCheckout {
 					DirCacheEntry entry = i.getDirCacheEntry();
 					if (entry.getLastModified() == 0)
 						entry.setLastModified(f.getEntryLastModified());
-					keep(entry);
+					keep(entry, f);
 				}
 			} else
 				// The index contains a folder
-				keep(i.getDirCacheEntry());
+				keep(i.getDirCacheEntry(), f);
 		} else {
 			// There is no entry in the merge commit. Means: we want to delete
 			// what's currently in the index and working tree
@@ -821,14 +823,14 @@ public class DirCacheCheckout {
 
 				break;
 			case 0xDFD: // 3 4
-				keep(dce);
+				keep(dce, f);
 				break;
 			case 0xF0D: // 18
 				remove(name);
 				break;
 			case 0xDFF: // 5 5b 6 6b
 				if (equalIdAndMode(iId, iMode, mId, mMode))
-					keep(dce); // 5 6
+					keep(dce, f); // 5 6
 				else
 					conflict(name, dce, h, m); // 5b 6b
 				break;
@@ -858,7 +860,7 @@ public class DirCacheCheckout {
 					conflict(name, dce, h, m); // 9
 				break;
 			case 0xFD0: // keep without a rule
-				keep(dce);
+				keep(dce, f);
 				break;
 			case 0xFFD: // 12 13 14
 				if (equalIdAndMode(hId, hMode, iId, iMode))
@@ -878,7 +880,7 @@ public class DirCacheCheckout {
 					conflict(name, dce, h, m);
 				break;
 			default:
-				keep(dce);
+				keep(dce, f);
 			}
 			return;
 		}
@@ -964,7 +966,7 @@ public class DirCacheCheckout {
 					if (initialCheckout)
 						update(name, mId, mMode);
 					else
-						keep(dce);
+						keep(dce, f);
 				} else
 					conflict(name, dce, h, m);
 			}
@@ -1027,7 +1029,7 @@ public class DirCacheCheckout {
 						// Nothing in Head
 						// Something in Index
 						// -> Merge contains nothing new. Keep the index.
-						keep(dce);
+						keep(dce, f);
 				} else
 					// Merge contains something and it is not the same as Index
 					// Nothing in Head
@@ -1176,7 +1178,7 @@ public class DirCacheCheckout {
 					// to the other one.
 					// -> In all three cases we don't touch index and file.
 
-					keep(dce);
+					keep(dce, f);
 				}
 			}
 		}
@@ -1225,9 +1227,15 @@ public class DirCacheCheckout {
 		}
 	}
 
-	private void keep(DirCacheEntry e) {
+	private void keep(DirCacheEntry e, WorkingTreeIterator f)
+			throws IOException {
 		if (e != null && !FileMode.TREE.equals(e.getFileMode()))
 			builder.add(e);
+		if (force) {
+			if (f.isModified(e, true, this.walk.getObjectReader())) {
+				checkoutEntry(repo, e, this.walk.getObjectReader());
+			}
+		}
 	}
 
 	private void remove(String path) {
@@ -1262,6 +1270,20 @@ public class DirCacheCheckout {
 	}
 
 	/**
+	 * If <code>true</code>, dirty worktree files may be overridden. If
+	 * <code>false</code> dirty worktree files will not be overridden in order
+	 * not to delete unsaved content. This corresponds to native git's 'git
+	 * checkout -f' option. By default this option is set to false.
+	 *
+	 * @param force
+	 *            a boolean.
+	 * @since 5.3
+	 */
+	public void setForce(boolean force) {
+		this.force = force;
+	}
+
+	/**
 	 * This method implements how to handle conflicts when
 	 * {@link #failOnConflict} is false
 	 *