[Doc] Revamp userman's chapter on reporting errors (BTS -> Gitlab)

doc/userman/user-errors.tex

 \chapter{Reporting Errors}
 \label{user-errors}
 
-If \FramaC crashes or behaves abnormally, you are invited to report a bug \via
-the \FramaC Bugs Tracking System (BTS) located at
-\url{http://bts.frama-c.com}. 
+If \FramaC crashes or behaves abnormally, you are invited to report an issue
+\via the \FramaC Gitlab repository, located at \url{https://git.frama-c.com}.
+The {\em New Issue} page (\url{https://git.frama-c.com/pub/frama-c/issues/new})
+allows creating a new report, but you will need an account.
 
 \begin{important}
-Opening a BTS account is required for such a task. 
+  Unless you have an account provided by the \FramaC team, you need to sign in
+  using a Github account, as shown in Figure~\ref{fig:gitlab-login}.
 \end{important}
 
-Bug reports can be marked as public or private.
-Public bug reports can be read by anyone and are indexed by search
-engines. Private bug reports are only shown to \FramaC developers. 
-
-Reporting a new issue opens a webpage similar to the one shown in
-Figure~\ref{fig:bts}.
 \begin{figure}[htbp]
 \begin{center}
-\includegraphics[width=\textwidth]{bts.pdf}
+\includegraphics[width=\textwidth]{gitlab-login.png}
 \end{center}
-\caption{The BTS Bugs Reporting Page}
-\label{fig:bts}
+\caption{The \FramaC Gitlab login page. Note that no direct account creation
+  is possible; you need to sign in via Github unless the \FramaC team
+  provided you an account.}
+\label{fig:gitlab-login}
 \end{figure}
-This page also has a link to an advanced bugs reporting page that allows you to
-write a more detailed report. The different fields of these forms shall be
-filled \emph{in English}\footnote{French is also a possible language choice for private entries.}
-as precisely as possible, in order for the maintenance team to understand and
-track the problem down easily.
-
-Below are some recommendations for this purpose\footnote{You can also have a
-  look at the associated \FramaC wiki:
-  \url{http://bts.frama-c.com/dokuwiki/doku.php?id=mantis:frama-c:start}.}:
-
-\begin{description}
-
-\item[Category:] select as appropriate.
-
-\item[Reproducibility:] select as appropriate.
-
-\item[Severity:] select the level of severity. Levels are shown in increasing
-  order of severity.
-
-\item[Profile or Platform, OS and OS Version:] enter your hardware and OS
-  characteristics.
-
-\item[Product Version and Product Build] this can be obtained with the
-  command \texttt{frama-c -version}\optionidx{-}{version}, see
-  Section~\ref{sec:version}.
-
-\item[Summary:] give a brief one line description of the nature of your bug.
 
-\item[Description:] first, explain the \textit{actual behavior}, that is what
-  you actually observe on your system. Then, describe your \textit{expected
-    behavior} of \FramaC, that is the results you expect instead. A ``bug'' is
-  sometimes due to a misunderstanding of the tool's behaviour or a
-  misunderstanding of its results, so providing both behaviors is an essential
-  part of the report. Please do clearly separate both parts in the description.
+When creating a new issue, choose the \texttt{bug\_report} template next to
+{\em Title}, then enter the title and fill the template.
 
-\item[Steps to reproduce:] provide everything necessary for a maintainer to
-  reproduce the bug: input files, commands used, sequence of actions, \etc.  If
-  the bug appears through the \FramaC GUI, it may be useful to attach the
-  generated journal (see Section~\ref{sec:journal}). Beware that this journal
-  \textbf{does not} replace nor contain the input files, that must be added to
-  the bug report too (see below).
+Bug reports can be marked as public or confidential.
+Public bug reports can be read by anyone and may be indexed by search
+engines. Confidential bug reports are only shown to \FramaC developers.
 
-\item[Additional Information:] any extra information that might help the
-  maintainer.
-
-\item[Industrial:] set it to \texttt{true} if you have a maintenance contract
-  with the \FramaC development team.
-
-\item[Upload File:] click on the \texttt{Browse} button to select a file for
-  uploading.  Typically, this is an archive that contains all files necessary
-  for reproducing your problem. It can include \C source files, shell scripts
-  to run \FramaC with your options and environment, a \FramaC journal,
-  \etc. Please check the size of the archive in order to keep it manageable:
-  leave out any object code or executable files that can be easily rebuilt
-  automatically (by a shell script for instance).
-
-\item[View Status:] set it to \texttt{private} if your bug should not be
-  visible by others users. Only yourself and the \FramaC developers will be
-  able to see your bug report.
-
-\item[Report Stay:] tick if this report shall remain open for further
-  additions.
+Reporting a new issue opens a webpage similar to the one shown in
+Figure~\ref{fig:gitlab-bug-report}.
+\begin{figure}[htbp]
+\begin{center}
+\includegraphics[width=\textwidth]{gitlab-bug-report.png}
+\end{center}
+\caption{The Gitlab new issue page, with the \texttt{bug\_report} template.
+  The checkbox at the bottom enables marking the issue as private, so that
+  only \FramaC developers can see it.}
+\label{fig:gitlab-bug-report}
+\end{figure}
 
-\end{description}
+Please fill the template as precisely as possible,
+\emph{in English}\footnote{French is also a possible language choice for
+  private entries.}, which helps the \FramaC team more quickly understand,
+reproduce and respond to the issue. The form uses Markdown syntax and you can
+attach source files and screenshots to the issue.
 
-After submitting the report you will be notified by e-mail about its progress
-and enter interactive mode on the BTS if necessary.
+Replies and updates concerning your issue are sent by e-mail by Gitlab.
 
 %% Local Variables:
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doc/userman/user-intro.tex

@@ -53,6 +53,6 @@ The remainder of this manual is organized in several chapters.
   the platform.
 \item[Chapter~\ref{user-gui}] gives a detailed description of the graphical
   user interface of \FramaC.
-\item[Chapter~\ref{user-errors}] explains how to report errors \via the
-  \FramaC's Bug Tracking System.
+\item[Chapter~\ref{user-errors}] explains how to report errors \via \FramaC's
+  public Gitlab repository.
 \end{description}