in src/main/kotlin/com/jetbrains/interactiveRebase/services/ActionService.kt [208:220]
fun checkValidParent(): Boolean {
if (modelService.branchInfo.getActualSelectedCommitsSize() != 1) return true
var commit = modelService.getLastSelectedCommit()
if (commit == modelService.getCurrentCommits().last()) {
return false
}
commit = getParent()
return !commit.isCollapsed && commit.getChangesAfterPick().filterIsInstance<DropCommand>().isEmpty()
}