Externalize error messages used in DfsGarbageCollector

Change-Id: I11631afb33a2bb29d994551a0be8775bbe277300
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties

 fileIsTooBigForThisConvenienceMethod=File is too big for this convenience method ({0} bytes).
 fileIsTooLarge=File is too large: {0}
 fileModeNotSetForPath=FileMode not set for path {0}
+findingGarbage=Finding garbage
 flagIsDisposed={0} is disposed.
 flagNotFromThis={0} not from this.
 flagsAlreadyCreated={0} flags already created.
 submoduleExists=Submodule ''{0}'' already exists in the index
 submoduleParentRemoteUrlInvalid=Cannot remove segment from remote url ''{0}''
 submodulesNotSupported=Submodules are not supported
+supportOnlyPackIndexVersion2=Only support index version 2
 symlinkCannotBeWrittenAsTheLinkTarget=Symlink "{0}" cannot be written as the link target cannot be read from within Java.
 systemConfigFileInvalid=Systen wide config file {0} is invalid {1}
 tagAlreadyExists=tag ''{0}'' already exists

org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java

 	/***/ public String fileIsTooBigForThisConvenienceMethod;
 	/***/ public String fileIsTooLarge;
 	/***/ public String fileModeNotSetForPath;
+	/***/ public String findingGarbage;
 	/***/ public String flagIsDisposed;
 	/***/ public String flagNotFromThis;
 	/***/ public String flagsAlreadyCreated;
 	/***/ public String submoduleExists;
 	/***/ public String submodulesNotSupported;
 	/***/ public String submoduleParentRemoteUrlInvalid;
+	/***/ public String supportOnlyPackIndexVersion2;
 	/***/ public String symlinkCannotBeWrittenAsTheLinkTarget;
 	/***/ public String systemConfigFileInvalid;
 	/***/ public String tagAlreadyExists;

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsGarbageCollector.java

 import java.util.Map;
 import java.util.Set;
 
+import org.eclipse.jgit.internal.JGitText;
 import org.eclipse.jgit.internal.storage.dfs.DfsObjDatabase.PackSource;
 import org.eclipse.jgit.internal.storage.file.PackIndex;
 import org.eclipse.jgit.internal.storage.pack.PackExt;
 		if (pm == null)
 			pm = NullProgressMonitor.INSTANCE;
 		if (packConfig.getIndexVersion() != 2)
-			throw new IllegalStateException("Only index version 2");
+			throw new IllegalStateException(
+					JGitText.get().supportOnlyPackIndexVersion2);
 
 		ctx = (DfsReader) objdb.newReader();
 		try {
 				RevWalk pool = new RevWalk(ctx)) {
 			pw.setDeltaBaseAsOffset(true);
 			pw.setReuseDeltaCommits(true);
-			pm.beginTask("Finding garbage", objectsBefore());
+			pm.beginTask(JGitText.get().findingGarbage, objectsBefore());
 			for (DfsPackFile oldPack : packsBefore) {
 				PackIndex oldIdx = oldPack.getPackIndex(ctx);
 				for (PackIndex.MutableEntry ent : oldIdx) {