Tk421 Tk421 - 6 months ago 66x
Java Question

File diff against the last commit with JGit

I am trying to use JGit to get the differences of a file from the last commit to the most recent uncommitted changes. How can I do this with JGit? (using the command line would be the output of

git diff HEAD

Following several discussions (link1, link2) I come with a piece of code that is able to find the files that are uncommited, but it I cannot get the difference of the files

Repository db = new FileRepository("/path/to/git");
Git git = new Git(db);

AbstractTreeIterator oldTreeParser = this.prepareTreeParser(db, Constants.HEAD);

List<DiffEntry> diff = git.diff().setOldTree(oldTreeParser).call();

for (DiffEntry entry : diff) {
System.out.println("Entry: " + entry + ", from: " + entry.getOldId() + ", to: " + entry.getNewId());
DiffFormatter formatter = new DiffFormatter(System.out);



The following setup works for me:

DiffFormatter formatter = new DiffFormatter( System.out );
formatter.setRepository( git.getRepository() );
AbstractTreeIterator commitTreeIterator = prepareTreeParser( git.getRepository(),  Constants.HEAD );
FileTreeIterator workTreeIterator = new FileTreeIterator( git.getRepository() );
List<DiffEntry> diffEntries = formatter.scan( commitTreeIterator, workTreeIterator );

for( DiffEntry entry : diffEntries ) {
  System.out.println( "Entry: " + entry + ", from: " + entry.getOldId() + ", to: " + entry.getNewId() );
  formatter.format( entry );

The uncommitted changes are made accessible trough the FileTreeIterator. Using formatter.scan() instead of the DiffCommand has the advantage that the formatter is set up properly to handle the FileTreeIterator. Otherwise you will get MissingObjectExceptions as the formatter tries to locate changes from the work tree in the repository.