public void prune()

in org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/GC.java [492:644]
119 lines of code
33 McCabe index (conditional complexity)

	public void prune(Set<ObjectId> objectsToKeep) throws IOException,
			ParseException {
		long expireDate = getExpireDate();

		// Collect all loose objects which are old enough, not referenced from
		// the index and not in objectsToKeep
		Map<ObjectId, File> deletionCandidates = new HashMap<>();
		Set<ObjectId> indexObjects = null;
		File objects = repo.getObjectsDirectory();
		String[] fanout = objects.list();
		if (fanout == null || fanout.length == 0) {
			return;
		}
		pm.beginTask(JGitText.get().pruneLooseUnreferencedObjects,
				fanout.length);
		try {
			for (String d : fanout) {
				checkCancelled();
				pm.update(1);
				if (d.length() != 2)
					continue;
				File dir = new File(objects, d);
				File[] entries = dir.listFiles();
				if (entries == null || entries.length == 0) {
					FileUtils.delete(dir, FileUtils.IGNORE_ERRORS);
					continue;
				}
				for (File f : entries) {
					checkCancelled();
					String fName = f.getName();
					if (fName.length() != Constants.OBJECT_ID_STRING_LENGTH - 2)
						continue;
					if (repo.getFS().lastModifiedInstant(f)
							.toEpochMilli() >= expireDate) {
						continue;
					}
					try {
						ObjectId id = ObjectId.fromString(d + fName);
						if (objectsToKeep.contains(id))
							continue;
						if (indexObjects == null)
							indexObjects = listNonHEADIndexObjects();
						if (indexObjects.contains(id))
							continue;
						deletionCandidates.put(id, f);
					} catch (IllegalArgumentException notAnObject) {
						// ignoring the file that does not represent loose
						// object
					}
				}
			}
		} finally {
			pm.endTask();
		}

		if (deletionCandidates.isEmpty()) {
			return;
		}

		checkCancelled();

		// From the set of current refs remove all those which have been handled
		// during last repack(). Only those refs will survive which have been
		// added or modified since the last repack. Only these can save existing
		// loose refs from being pruned.
		Collection<Ref> newRefs;
		if (lastPackedRefs == null || lastPackedRefs.isEmpty())
			newRefs = getAllRefs();
		else {
			Map<String, Ref> last = new HashMap<>();
			for (Ref r : lastPackedRefs) {
				last.put(r.getName(), r);
			}
			newRefs = new ArrayList<>();
			for (Ref r : getAllRefs()) {
				Ref old = last.get(r.getName());
				if (!equals(r, old)) {
					newRefs.add(r);
				}
			}
		}

		if (!newRefs.isEmpty()) {
			// There are new/modified refs! Check which loose objects are now
			// referenced by these modified refs (or their reflogentries).
			// Remove these loose objects
			// from the deletionCandidates. When the last candidate is removed
			// leave this method.
			ObjectWalk w = new ObjectWalk(repo);
			try {
				for (Ref cr : newRefs) {
					checkCancelled();
					w.markStart(w.parseAny(cr.getObjectId()));
				}
				if (lastPackedRefs != null)
					for (Ref lpr : lastPackedRefs) {
						w.markUninteresting(w.parseAny(lpr.getObjectId()));
					}
				removeReferenced(deletionCandidates, w);
			} finally {
				w.dispose();
			}
		}

		if (deletionCandidates.isEmpty())
			return;

		// Since we have not left the method yet there are still
		// deletionCandidates. Last chance for these objects not to be pruned is
		// that they are referenced by reflog entries. Even refs which currently
		// point to the same object as during last repack() may have
		// additional reflog entries not handled during last repack()
		ObjectWalk w = new ObjectWalk(repo);
		try {
			for (Ref ar : getAllRefs())
				for (ObjectId id : listRefLogObjects(ar, lastRepackTime)) {
					checkCancelled();
					w.markStart(w.parseAny(id));
				}
			if (lastPackedRefs != null)
				for (Ref lpr : lastPackedRefs) {
					checkCancelled();
					w.markUninteresting(w.parseAny(lpr.getObjectId()));
				}
			removeReferenced(deletionCandidates, w);
		} finally {
			w.dispose();
		}

		if (deletionCandidates.isEmpty())
			return;

		checkCancelled();

		// delete all candidates which have survived: these are unreferenced
		// loose objects. Make a last check, though, to avoid deleting objects
		// that could have been referenced while the candidates list was being
		// built (by an incoming push, for example).
		Set<File> touchedFanout = new HashSet<>();
		for (File f : deletionCandidates.values()) {
			if (f.lastModified() < expireDate) {
				f.delete();
				touchedFanout.add(f.getParentFile());
			}
		}

		for (File f : touchedFanout) {
			FileUtils.delete(f,
					FileUtils.EMPTY_DIRECTORIES_ONLY | FileUtils.IGNORE_ERRORS);
		}

		repo.getObjectDatabase().close();
	}