Added dirty-detection to WorkingTreeIterator

Added possibility to compare the current entry of a WorkingTreeIterator
to a given DirCacheEntry. This is done to detect whether an entry
in the index is dirty or not. 'Dirty' means that the file in the working tree
is different from what's in the index. Merge algorithms will make use of
this to detect conflicts.

Change-Id: I3ff847f4bf392553dcbd6ee236c6ca32a13eedeb
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit/src/org/eclipse/jgit/treewalk/WorkingTreeIterator.java

@@ -1,5 +1,7 @@
 /*
  * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
+ * Copyright (C) 2010, Christian Halstrick <christian.halstrick@sap.com>
+ * Copyright (C) 2010, Matthias Sohn <matthias.sohn@sap.com>
  * and other copyright owners as documented in the project's IP log.
  *
  * This program and the accompanying materials are made available
@@ -55,9 +57,12 @@ import java.util.Arrays;
 import java.util.Comparator;
 
 import org.eclipse.jgit.JGitText;
+import org.eclipse.jgit.dircache.DirCache;
+import org.eclipse.jgit.dircache.DirCacheEntry;
 import org.eclipse.jgit.errors.CorruptObjectException;
 import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.FileMode;
+import org.eclipse.jgit.util.FS;
 
 /**
  * Walks a working directory tree as part of a {@link TreeWalk}.
@@ -363,6 +368,71 @@ public abstract class WorkingTreeIterator extends AbstractTreeIterator {
 		return entries[ptr];
 	}
 
+	/**
+	 * Checks whether this entry differs from a given entry from the
+	 * {@link DirCache}.
+	 *
+	 * File status information is used and if status is same we consider the
+	 * file identical to the state in the working directory. Native git uses
+	 * more stat fields than we have accessible in Java.
+	 *
+	 * @param entry
+	 *            the entry from the dircache we want to compare against
+	 * @param forceContentCheck
+	 *            True if the actual file content should be checked if
+	 *            modification time differs.
+	 * @param checkFilemode
+	 *            whether the executable-bit in the filemode should be checked
+	 *            to detect modifications
+	 * @param fs
+	 *            The filesystem this repo uses. Needed to find out whether the
+	 *            executable-bits are supported
+	 *
+	 * @return true if content is most likely different.
+	 */
+	public boolean isModified(DirCacheEntry entry, boolean forceContentCheck,
+			boolean checkFilemode, FS fs) {
+		if (entry.isAssumeValid())
+			return false;
+
+		if (entry.isUpdateNeeded())
+			return true;
+
+		if (getEntryLength() != entry.getLength())
+			return true;
+
+		// determine difference in mode-bits of file and index-entry. In the
+		// bitwise presentation of modeDiff we'll have a '1' when the two modes
+		// differ at this position.
+		int modeDiff = getEntryRawMode() ^ entry.getRawMode();
+		// ignore the executable file bits if checkFilemode tells me to do so.
+		// Ignoring is done by setting the bits representing a EXECUTABLE_FILE
+		// to '0' in modeDiff
+		if (!checkFilemode)
+			modeDiff &= ~FileMode.EXECUTABLE_FILE.getBits();
+		if (modeDiff != 0)
+			// report a modification if the modes still (after potentially
+			// ignoring EXECUTABLE_FILE bits) differ
+			return true;
+
+		// Git under windows only stores seconds so we round the timestamp
+		// Java gives us if it looks like the timestamp in index is seconds
+		// only. Otherwise we compare the timestamp at millisecond precision.
+		long cacheLastModified = entry.getLastModified();
+		long fileLastModified = getEntryLastModified();
+		if (cacheLastModified % 1000 == 0)
+			fileLastModified = fileLastModified - fileLastModified % 1000;
+		if (forceContentCheck) {
+			if (fileLastModified == cacheLastModified)
+				return false; // Same time, don't check content.
+			else
+				return !getEntryObjectId().equals(entry.getObjectId());
+		} else {
+			// No content check forced, assume dirty if stat differs.
+			return fileLastModified != cacheLastModified;
+		}
+	}
+
 	/** A single entry within a working directory tree. */
 	protected static abstract class Entry {
 		byte[] encodedName;