doc: add 2020.2.1 release notes

doc/2020.2.html

@@ -10,6 +10,7 @@
 	  <li><a href="#checks-new">New checks</a></li>
 	  <li><a href="#checks-changed">Changed checks</a></li>
   </ul></li>
+  <li><a href="#2020.2.1">Staticcheck 2020.2.1 release notes</a></li>
 </ul>
 
 <h2 id="performance-improvements">Performance improvements</h2>
@@ -560,3 +561,21 @@ <h3 id="checks-changed">Changed checks</h3>
   <li>Incorrect position information in various checks have been fixed</li>
   <li>Crashes in various checks have been fixed</li>
 </ul>
+
+<h2 id="2020.2.1">Staticcheck 2020.2.1 release notes</h2>
+
+<p>
+  This release eliminates some false negatives as well as false positives, makes the <code>staticcheck</code> command less noisy and fixes a potential security issue.
+</p>
+
+<ul>
+  <li>{{ check "SA4020" }} no longer claims that <code>case nil</code> is an unreachable case in a type switch.</li>
+  <li>{{ check "S1025" }} no longer marks uses of Printf as unnecessary when the printed types implement the <code>fmt.Formatter</code> interface.</li>
+  <li>Various checks may now detect bugs in conditional code that were previously missed. This was a regression introduced in Staticcheck 2020.1.</li>
+  <li>The <code>staticcheck</code> command no longer reminds the user of the <code>-explain</code> flag every time problems are found. This was deemed too noisy.</li>
+  <li>
+	We've updated our dependency on <code>golang.org/x/tools</code> to guard against arbitrary code execution on Windows.
+	Note that to be fully safe, you will also have to update your installation of Go.
+	See the <a href="https://blog.golang.org/path-security">Command PATH security in Go</a> article by the Go authors for more information on this potential vulnerability.
+  </li>
+</ul>

doc/staticcheck.html

@@ -22,12 +22,12 @@ <h2 id="installation">Installation</h2>
 <p>
   If you use Go modules, you can simply run <code>go get honnef.co/go/tools/cmd/staticcheck</code> to obtain the latest released version.
   If you're still using a GOPATH-based workflow, then the above command will instead fetch the master branch.
-  It is suggested that you explicitly check out the latest release tag instead, which is currently <code>2020.2</code>.
+  It is suggested that you explicitly check out the latest release tag instead, which is currently <code>2020.2.1</code>.
   One way of doing so would be as follows:
 </p>
 
 <pre><code>cd $GOPATH/src/honnef.co/go/tools/cmd/staticcheck
-git checkout 2020.2
+git checkout 2020.2.1
 go get
 go install
 </code></pre>