.revisions {
    float: right;
    background-color: silver;
    padding: 1em;
}

#form-revisions {
    display: none;
}

#form-revisions ~ label.form-revisions::after {
    content: "...";
}

#form-revisions:checked ~ label.form-revisions::after {
    content: ":";
}

#form-revisions:checked ~ .revision-list {
    display: block;
}

.revision-list {
    display: none;
}

.revision-list .revision {
    display: block;
}

.revision-list span.revision {
    font-weight: bold;
}