DOC: Rewrite "Work on an issue" section

Make that section more understandable and actionable
for people unfamiliar with the GitHub interface and
the pull request process.

Author: timhoffm

doc/devel/contribute.rst

@@ -154,12 +154,19 @@ Work on an issue
 ----------------
 
 In general, the Matplotlib project does not assign issues. Issues are
-"assigned" or "claimed" by opening a PR; there is no other assignment
-mechanism. If you have opened such a PR, please comment on the issue thread to
-avoid duplication of work. Please check if there is an existing PR for the
-issue you are addressing. If there is, try to work with the author by
+"assigned" or "claimed" by
+:ref:`proposing a solution via a pull request <how-to-pull-request>` (PR).
+We ask PR authors to
+`link the PR to the issue
+<https://docs.github.com/en/issues/tracking-your-work-with-issues/linking-a-pull-request-to-an-issue>`_.
+Such links are be displayed in the discussion thread as well as the sidebar
+on the issue page on GitHub.
+
+Before starting to work on an issue, please check if there is already
+a linked PR. If there is, try to work with the author by
 submitting reviews of their code or commenting on the PR rather than opening
-a new PR; duplicate PRs are subject to being closed.  However, if the existing
+a new PR; duplicate PRs are unnecessary concurrent work and thus are subject
+to being closed.  However, if the existing
 PR is an outline, unlikely to work, or stalled, and the original author is
 unresponsive, feel free to open a new PR referencing the old one.
 
@@ -183,7 +190,7 @@ our code consistent and mitigating the impact of changes.
 * :ref:`pr-guidelines`
 
 Code is contributed through pull requests, so we recommend that you start at
-:ref:`how-to-contribute` If you get stuck, please reach out on the
+:ref:`how-to-pull-request` If you get stuck, please reach out on the
 :ref:`contributor_incubator`
 
 .. _contribute_documentation:
@@ -236,7 +243,7 @@ Instructions and guidelines for contributing documentation are found in:
 * :doc:`tag_guidelines`
 
 Documentation is contributed through pull requests, so we recommend that you start
-at :ref:`how-to-contribute`. If that feels intimidating, we encourage you to
+at :ref:`how-to-pull-request`. If that feels intimidating, we encourage you to
 `open an issue`_ describing what improvements you would make. If you get stuck,
 please reach out on the :ref:`contributor_incubator`
 
@@ -260,7 +267,7 @@ please follow the :doc:`/project/citing` guidelines.
 If you have developed an extension to Matplotlib, please consider adding it to our
 `third party package <https://github.com/matplotlib/mpl-third-party>`_  list.
 
-.. _how-to-contribute:
+.. _how-to-pull-request:
 
 How to contribute via pull request
 ==================================

doc/devel/index.rst

@@ -81,7 +81,7 @@ New contributors
 
       :octicon:`git-pull-request;1em;sd-text-info` :ref:`How do I claim an issue? <managing_issues_prs>`
 
-      :octicon:`codespaces;1em;sd-text-info` :ref:`How do I start a pull request? <how-to-contribute>`
+      :octicon:`codespaces;1em;sd-text-info` :ref:`How do I start a pull request? <how-to-pull-request>`
 
    .. grid-item::