[doc/release] clarification about local usage of opam repository

doc/release/website.tex

@@ -154,8 +154,8 @@ You'll need a GitHub account to create a pull request on the official opam repos
 \item Create a new directory: \\
   \texttt{packages/frama-c/frama-c.<version>} \\
 \item Copy the file \texttt{opam/opam} from the release
- to the opam repository clone in
- \texttt{packages/frama-c/frama-c.<version>/opam}.
+ to the opam repository clone in: \\
+ \texttt{packages/frama-c/frama-c.<version>/opam}
 \item Compute the MD5sum of the .tar.gz file and update the \texttt{opam} file
 with the following entry:
 \begin{verbatim}
@@ -175,6 +175,11 @@ opam install frama-c
 \end{verbatim}
 (of course, if you already create a local switch before and it uses your
 local version of the repository, you just have to switch to it).
+
+\textbf{Note:} uncommitted changes are ignored by \texttt{opam repository};
+you have to locally commit them before \texttt{opam update} will take them into
+account.
+
 \item Create a branch with any name you want (e.g. frama-c.<version>) and push it to your remote Github
 \item Create a pull request to opam-repository. If all tests pass,
   someone from opam should merge it for you.