Prune deleted folders of repo diff report using Java

Sometimes the contents of deleted folders are not relevant. Just showing the top level deleted folder or dir is enough. For example, in a branch diff against trunk, folder moves are shown as adds and deletes. But in a diff report, the whole sub node of the deleted folder is output.

In the particular report I was creating everything under the deleted directories was just noise. How to prune that?

BTW, I searched the SVN docs and found no support for this kind of pruning. I also looked at the Git docs to see if it was different, but also found no mention of this use-case.

Example scenario:

d1 (modified)
├ d2 (deleted)
   ┝ d3 (deleted)

If we create a deleted prune report of the above, it would contain, d1 modified, and d1/d2 deleted. It would not contain d1/d2/d3.

The algorithm in psuedocode

boolean deleting := false
String deletePath = “”

for each path{
    if deleting then 
            if path starts with deletePath then
                skip path
            else
                deleting = false
                deletePath = “”
                result.add(path)
            endif       
    else
        if path is directory and it is deleted then
            deleting = true
            deletePath = path
        endif
        
        result.add(path)
        
    endif
}

This can be implemented at the script level, for example, using Groovy or some other language.

SvnKit Scenario

In an Subversion Console application I wrote using ReactJS, I used SvnKit at the server side to interface to the Subversion server. Future blog post will discuss this single-page app. One of the React components was a Diff table.

Using the SvnKit library I generated an svn diff summary list. This is a list of SvnDiffStatus objects: List. Among other things, these object contain a path string of the respective resource.

To prune the excess deleted folders I first attempted to create an Object tree structure, then I gave up on that (too slow), finally a co-worker suggested I just sort the paths and do a simple contains comparison. Wow, how did I miss that? I guess I was sidetracked by “Objects” and didn’t use simple scripting techniques.

So to prune the folders we sort and prune the results of an SvnDiffSummary object, svnDiff::
List list = pruneDeletedFolders(sortDiffList(((Receiver)svnDiff.getReceiver()).getEntries()));

Where Receiver is an implementation of ISvnObjectReceiver.

(The SvnDiff entries may already be sorted, but the SvnKit API docs do not specify this).

Sort the diff list using Guava

	private List<SvnDiffStatus> sortDiffList(List<SvnDiffStatus> list) {
		return new Ordering<SvnDiffStatus>() {
			@Override
			public int compare(SvnDiffStatus left, SvnDiffStatus right) {
				return left.getPath().compareTo(right.getPath());
			}
		}.sortedCopy(list);
	}

prune the list

	private List<SvnDiffStatus> pruneDeletedFolders(List<SvnDiffStatus> list){
		String deletedPath = "";
		boolean isDeleting = false;
		
		List<SvnDiffStatus> prunedList = new ArrayList<>();

		for (Iterator<SvnDiffStatus> iterator = list.iterator(); iterator.hasNext();) {
			SvnDiffStatus diff = iterator.next();
			String path = diff.getPath();
			if (isDeleting) {
				if (path.startsWith(deletedPath)) {
					// skip this diff
				} else {
					isDeleting = false;
					deletedPath = "";
					prunedList.add(diff);
				}
			} else {
				if (isDirectory(diff) && isStatusDeleted(diff)) {
					isDeleting = true;
					deletedPath = path;
				}

				prunedList.add(diff);
			}
		}

		return prunedList;

	}

Links

• SVNKit
• ReactJS
• Guava
• Subversion
• Git