Bookmarklet for Gerrit that displays all changesets for a certain Change-Id. This way you can link commits across different projects.

display-all-changes.js

function getChangeId(container) {
    for (var i in container.childNodes) {
        var node = container.childNodes[i];
        if (node.nodeName === 'P' &&
                node.innerText.indexOf('Change-Id:') === 0) {
            var changeId = node.innerText.substr('Change-Id: '.length, 41);
            return changeId;
        }
    }
    return 'error';
};

function sendRequest(requestData, cb) {
    var xhr = new XMLHttpRequest();
    xhr.open('POST', window.location.origin + '/' + 'gerrit/rpc/ChangeListService');
    xhr.setRequestHeader('Content-type', 'application/json;charset=UTF-8');
    xhr.setRequestHeader('Accept', 'application/json');
    xhr.onreadystatechange = function() {
        if (xhr.readyState !== 4) {
            return;
        }
        var resp = JSON.parse(xhr.responseText);
        cb(resp);
    };
    xhr.send(JSON.stringify(requestData));
}

function createItem(url, infoText) {
    var link = document.createElement('a');
    var info = document.createTextNode(infoText);
    var item = document.createElement('li');

    link.href = url;
    link.innerText = url;
    item.appendChild(link);
    item.appendChild(info);
    return item;
}

function insertItems(container, items) {
    var list = document.createElement('ul');
    for (var i in items) {
        list.appendChild(items[i]);
    }
    container.appendChild(list);
}

function displayAllChanges() {
    var container = document.getElementsByClassName("GJEA35ODLB")[0];
    var changeId = getChangeId(container);
    var requestData = {
        jsonrpc: "2.0",
        method: "allQueryNext",
        params: [changeId, "z", 0],
        id: 2
    };

    sendRequest(requestData, function(resp) {
        var items = resp.result.changes.map(function(change) {
            var url = window.location.origin + '/' + change.id.id;
            var info = ' (' + change.project.key.name + ', ' +
                change.status + ')';
            var item = createItem(url, info);
            return item;
        });
        insertItems(container, items);
    });
}
displayAllChanges();