private void reword()

in org.eclipse.egit.core/src/org/eclipse/egit/core/op/RewordCommitOperation.java [105:235]
119 lines of code
28 McCabe index (conditional complexity)

	private void reword(IProgressMonitor monitor, RevWalk walk)
			throws IOException, CoreException {
		SubMonitor progress = SubMonitor.convert(monitor, MessageFormat.format(
				CoreText.RewordCommitOperation_rewording,
				Utils.getShortObjectId(commit)), 100);

		commit = walk.parseCommit(commit);
		if (newMessage.equals(commit.getFullMessage())) {
			// Nothing to do.
			return;
		}
		Ref ref = repository.exactRef(Constants.HEAD);
		if (ref == null) {
			// No HEAD: cannot reword
			throw new TeamException(CoreText.RewordCommitOperation_noHead);
		}
		headId = ref.getObjectId();
		if (headId == null || ObjectId.zeroId().equals(headId)) {
			throw new TeamException(CoreText.RewordCommitOperation_noHead);
		}
		String headName = ref.isSymbolic() ? ref.getLeaf().getName()
				: headId.name();
		Deque<RevCommit> commits = new LinkedList<>();
		walk.setRetainBody(true);
		if (!commit.getId().equals(headId)) {
			walk.sort(RevSort.TOPO);
			walk.sort(RevSort.COMMIT_TIME_DESC, true);
			walk.markStart(walk.parseCommit(headId));
			for (RevCommit p : commit.getParents()) {
				RevCommit parsed = walk.parseCommit(p);
				walk.markUninteresting(parsed);
			}
			RevCommit c;
			while ((c = walk.next()) != null) {
				if (c.getId().equals(commit.getId())) {
					break;
				}
				commits.push(c);
			}
			if (c == null) {
				throw new TeamException(MessageFormat.format(
						CoreText.RewordCommitOperation_notReachable,
						Utils.getShortObjectId(commit)));
			}
		}
		progress.worked(10);
		progress.setWorkRemaining(commits.size() + 2);
		PersonIdent committer = new PersonIdent(repository);
		// Rewrite the message
		CommitBuilder builder = copy(commit, commit.getParents(), committer,
				newMessage);
		// Signature will be invalid for the new commit. Try to re-sign.
		File gpgProgram = GitSettings.getGpgExecutable();
		GpgConfig gpgConfig = new GpgConfig(repository.getConfig()) {

			@Override
			public String getProgram() {
				return gpgProgram != null ? gpgProgram.getAbsolutePath()
						: super.getProgram();
			}
		};
		boolean signAllCommits = gpgConfig.isSignCommits();
		GpgSigner gpgSigner = GpgSetup.getDefault();
		if (gpgSigner != null
				&& (signAllCommits || commit.getRawGpgSignature() != null)) {
			gpgSigner = sign(builder, gpgSigner, gpgConfig, committer, commit);
		}
		Map<ObjectId, ObjectId> rewritten = new HashMap<>();
		String newCommitId = null;
		try (ObjectInserter inserter = repository.newObjectInserter()) {
			ObjectId newCommit = inserter.insert(builder);
			rewritten.put(commit.getId(), newCommit);
			newCommitId = newCommit.name();
			progress.worked(1);
			// Now rewrite all others: fill in new parents
			for (RevCommit c : commits) {
				RevCommit[] parents = c.getParents();
				ObjectId[] newParents = new ObjectId[parents.length];
				int i = 0;
				boolean hadNew = false;
				for (RevCommit p : parents) {
					ObjectId newId = rewritten.get(p.getId());
					if (newId != null) {
						hadNew = true;
					}
					newParents[i++] = newId != null ? newId : p.getId();
				}
				if (!hadNew) {
					continue;
				}
				committer = new PersonIdent(committer); // Update when
				builder = copy(c, newParents, committer, c.getFullMessage());
				if (gpgSigner != null
						&& (signAllCommits || c.getRawGpgSignature() != null)) {
					gpgSigner = sign(builder, gpgSigner, gpgConfig, committer,
							c);
				}
				rewritten.put(c.getId(), inserter.insert(builder));
				progress.worked(1);
			}
			inserter.flush();
		}
		// Update HEAD, and write ORIG_HEAD
		ObjectId newHeadId = rewritten.get(headId);
		RefUpdate ru = repository.updateRef(Constants.HEAD);
		ru.setExpectedOldObjectId(headId);
		ru.setNewObjectId(newHeadId);
		ru.setForceUpdate(true);
		ru.setRefLogMessage("rebase finished: returning to " + headName //$NON-NLS-1$
				+ " after having reworded commit " + newCommitId, false); //$NON-NLS-1$
		switch (ru.update(walk)) {
		case NEW:
		case NO_CHANGE:
		case FORCED:
		case FAST_FORWARD:
			break;
		default:
			throw new TeamException(MessageFormat.format(
					CoreText.RewordCommitOperation_cannotUpdateHead,
					Utils.getShortObjectId(commit)));
		}
		ObjectId origHead = ru.getOldObjectId();
		if (origHead != null) {
			// TODO: JGit should handle ORIG_HEAD as a ref to guard against
			// concurrent modifications, or there should be a way to copy
			// the old head ObjectId atomically to ORIG_HEAD on the HEAD
			// update.
			repository.writeOrigHead(origHead);
		}
		progress.worked(1);
	}