sagemathgh-36292: Fix sync labels issues for step 2 going live comple…

…tion

    
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Unfortunately the fix in sagemath#36213 has
not been completed properly. There is still a `return` from the
`get_review_decision` method which is not `None` where it should be.

This is fixed here. Sorry for this unnecessary trouble and my lack of
attention!

In a next step this PR fixes a bug which has been noticed by an
accidentally activation of the `unlabeled` trigger (see
sagemath#36292 (comment)).
Simultanously the `labeled`-trigger has been disabled. This is an
unrealistic setting which was not covered by the code.

Explicitely, a state label could not be removed even though other state
labels where set (examples  sagemath#36128
and sagemath#36020). This PR leads to the
following changes of behavior:

1. The reaction on the `unlabeled`-event is reduced to the case of the
last label
2. The `unlabeled`-event will not lead to a rejection of the removal any
more
3. Instead of a warning comment a hint comment is posted.

We found a way to test the bot a little more realistically (see
soehms#11). Additional problems emerged and
were also resolved. This led to the following changes in the workflow:


4. A bug in `actor_valid` is fixed (see
soehms#10 (comment))
5. Preparing to use our own bot user (e.g.
[sagemathadmins](https://github.com/sagemathadmins)) (see
soehms#11 (comment))
6. Waiver of observing the `reviewDecision` feature provided by GitHub
(see 2. in
soehms#11 (comment))
7. Allow the user to revert his decision of label selection (see
soehms#11 (comment))
8. Don't reject label addition any more, except in the case where the
author tries to set `s: positive review` to his own PR which has no
reviews from others (see
soehms#11 (comment))
9. Dismiss stale reviews of the bot after a push to the branch and on
submission of a new review which is more than just a comment (see
soehms#11 (comment)).

Despite the fact that the testing was now more realistic, it is still
not guaranteed that the bot's behavior in `sagemath/sage` will be
completely covered by our testing.

The changes in this PR cannot be activated immediately after merging
into the develop branch due to a bug in the GitHub web interface
observed during testing in soehms#11 (see
soehms#11 (comment) and
soehms#11 (comment)). The
problem is that the panel at the top right of the webpage that contains
the labels does not update immediately after the bot changes the labels.
Since this might cause confusion, I'll create a bug report about it. The
going-live of the sync bot will be stalled at least until we received an
answer.

This PR changes the following flowcharts from
sagemath#35172 :

##### What happens when adding `s: needs review` to a PR?

```mermaid
---
title: add the needs review label
---
flowchart LR

%% vertices

    trigger([label\n 's: needs review'\n added])
    mark_as_ready([mark as\n ready for\n review])
    remove_other_labels([remove other\n state labels])
    warning_about_label_addition([warning\n about label\n addition])
    needs_review_valid[[needs review\n valid?]]
    is_draft{is PR\n a draft?}

%% edges

    trigger --> needs_review_valid
    needs_review_valid -- true ---> remove_other_labels
    needs_review_valid -- false ---> is_draft
    is_draft -- yes ---> mark_as_ready
    is_draft -- no ---> warning_about_label_addition
    mark_as_ready --> remove_other_labels
```


The warning is posted as a comment which will be deleted after 5
minutes.




```mermaid
---
title: needs review valid?
---
flowchart LR

%% vertices

    needs_review_valid([needs review\n valid?])
    true([true])
    false([false])
    latest_review_by_actor{latest review\n by actor}
    needs_work_valid[[needs work\n valid?]]
    positive_review_valid[[positive review\n valid?]]
    is_draft{is PR\n a draft?}

%% edges

    needs_review_valid ---> is_draft
    is_draft -- yes ---> false
    is_draft -- no ---> latest_review_by_actor
    latest_review_by_actor -- yes ---> true
    latest_review_by_actor -- no ---> needs_work_valid
    needs_work_valid -- true ---> false
    needs_work_valid -- false ---> positive_review_valid
    positive_review_valid -- true ---> false
    positive_review_valid -- false ---> true
```

```mermaid
---
title: needs work valid?
---
flowchart LR

%% vertices

    needs_work_valid([needs work\n valid?])
    true([true])
    false([false])
    latest_review_request_changes{latest proper\n review requests\n
changes?}

%% edges

    needs_work_valid  --> latest_review_request_changes
    latest_review_request_changes -- yes ---> true
    latest_review_request_changes -- no ---> false
```


```mermaid
---
title: positive review valid?
---
flowchart LR

%% vertices

    positive_review_valid([positive review\n valid?])
    true([true])
    false([false])
    latest_proper_review_approved{latest proper\n review\n approved?}

%% edges

    positive_review_valid  --> latest_proper_review_approved
    latest_proper_review_approved -- yes ---> true
    latest_proper_review_approved -- no ---> false
```

Here, proper means that the review is more than a comment.

##### What happens when adding s: needs work to a PR?


```mermaid
---
title: add the needs work label
---
flowchart LR

%% vertices

    trigger([label\n 's: needs work'\n added])
    request_changes([request changes])
    remove_other_labels([remove other\n state labels])
    warning_about_label_addition([warning\n about label\n addition])
    needs_work_valid[[needs work\n valid?]]
    is_draft{is PR\n a draft?}

%% edges

    trigger --> needs_work_valid
    needs_work_valid -- true ---> remove_other_labels
    needs_work_valid -- false ---> is_draft
    is_draft -- yes ---> warning_about_label_addition
    is_draft -- no ---> request_changes
    request_changes --> remove_other_labels
```

##### What happens when adding `s: positive review` to a PR?

```mermaid
---
title: add the positive review label
---
flowchart LR

%% vertices

    trigger([label\n 's: positive review'\n added])
    positive_review_valid[[positive review\n valid?]]
    approve_pr([approve])
    remove_other_labels([remove other\n state labels])
    actor_valid[[actor valid?]]
    approve_allowed[[approve\n allowed?]]
    warning_about_label_addition([warning\n about label\n addition])
    reject_label_addition[[reject\n label\n addition]]

%% edges

    trigger --> positive_review_valid
    positive_review_valid -- yes ---> remove_other_labels
    positive_review_valid -- no ---> actor_valid
    actor_valid -- yes ---> approve_allowed
    actor_valid -- no ---> reject_label_addition
    approve_allowed -- yes ---> approve_pr
    approve_allowed -- no ---> warning_about_label_addition
    approve_pr --> remove_other_labels
```

The boxes `actor_valid` and `reject_label_addition` are unchanged.


```mermaid
---
title: approve allowed?
---
flowchart LR

%% vertices

    trigger([approve\n allowed?])
    true([true])
    false([false])
    review_of_others_request_changes{changes\n requested by\n someone\n
else exists?}

%% edges

    trigger --> review_of_others_request_changes
    review_of_others_request_changes -- yes ---> false
    review_of_others_request_changes -- no ---> true
```

Here, only reviews of someone else are considered which are more recent
than any commit.



##### What happens when a state label is added to an issue?


```mermaid
---
title: add a state label to an issue
---
flowchart LR

%% vertices

    trigger([label added])
    warning_about_label_addition([warning\n about label\n addition])
    nothing([do nothing])
    is_needs_info{is label\n 's: needs info'?}

%% edges

    trigger --> is_needs_info
    is_needs_info -- yes --->  nothing
    is_needs_info -- no --->  warning_about_label_addition
```

##### What happens when removing a state label from a PR?

```mermaid
---
title: remove a state label
---
flowchart LR

%% vertices

    trigger([label removed])
    nothing([do nothing])
    hint_about_label_removal([hint\n about label\n removal])
    other_state_label{other state\n labels exist?}
    is_needs_info{is label\n 's: needs info'?}

%% edges

    trigger --> other_state_label
    other_state_label -- yes ---> nothing
    other_state_label -- no ---> is_needs_info
    is_needs_info -- yes --->  nothing
    is_needs_info -- no ---> hint_about_label_removal
```

The hint is postet as a comment which will be deleted after 5 minutes.

##### What happens when adding a priority label?

```mermaid
---
title: add a priority label
---
flowchart LR

%% vertices

    trigger([label added])
    remove_other_labels([remove other\n priority labels])

%% edges

    trigger --> remove_other_labels
```

##### What happens when removing a priority label?


```mermaid
---
title: remove a priority label
---
flowchart LR

%% vertices

    trigger([label removed])
    nothing([do nothing])
    hint_about_label_removal([hint\n about label\n removal])
    other_prio_label{other priority\n labels exist?}

%% edges

    trigger --> other_prio_label
    other_prio_label -- yes ---> nothing
    other_prio_label -- no ---> hint_about_label_removal
```

##### What happens when a PR is approved?

```mermaid
---
title: approve
---
flowchart LR

%% vertices

    trigger([approve\n])
    select_positive_review(['s: positive review'\n label selected])
    nothing([do nothing])
    positive_review_valid[[positive review\n valid?]]
    pending_review_requests{pending\n review requests\n exists?}
    actor_authorized{is actor\n a member of\n Triage?}

%% edges

    trigger ---> pending_review_requests
    pending_review_requests -- yes ---> nothing
    pending_review_requests -- no ---> actor_authorized
    actor_authorized -- yes ---> positive_review_valid
    actor_authorized -- no ---> nothing
    positive_review_valid -- true ---> select_positive_review
    positive_review_valid -- false ---> nothing
```


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### ⌛ Dependencies

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URL: sagemath#36292
Reported by: Sebastian Oehms
Reviewer(s): Kwankyu Lee