[analyzer] Update the documentation to show the command line option

[george.karpenkov]

Summary

There seems to be a very large amount of confusion on how to analyze just a single file from the command line. I think we should document this case, even if it's not the most supported workflow (as open-source users would find that in tutorials anyway)

[NoQ]

www/analyzer/faq.html

246–248

Ew. Should we support this in a better way, i.e. by adding a user-friendly driver flag?

Or just tell them to always use -o where (does it also require -Xclang)?

[NoQ]

www/analyzer/faq.html

233–234

Suggesting: "You can append --analyze to any compilation command. This would tell Clang to perform analysis instead of compilation. In other words, all usual clang flags...".

255–256

... but it won't generate index.html, which, according to my little observations, most novice users would expect to see. I still feel that we should recommend just pre-pending scan-build to the clang command as the first option.

[dcoughlin]

We don't consider --analyze to be public UI, which is why it is not documented. The supported interface to the analyzer is scan-build.

www/analyzer/faq.html

null?</a></li>
   <li><a href="#unused_ivar">How do I tell the static analyzer that I don't care about a specific unused instance variable in Objective C?</a></li>
   <li><a href="#unlocalized_string">How do I tell the static analyzer that I don't care about a specific unlocalized string?</a></li>
   <li><a href="#dealloc_mrr">How do I tell the analyzer that my instance variable does not need to be released in -dealloc under Manual Retain/Release?</a></li>
   <li><a href="#decide_nullability">How do I decide whether a method's return type should be _Nullable or _Nonnull?</a></li>
   <li><a href="#nullability_intentional_violation">How do I tell the analyzer that I am intentionally violating nullability?</a></li>
   <li><a href="#use_assert">The analyzer assumes that a loop body is never entered.  How can I tell it that the loop body will be entered at least once?</a></li>
   <li><a href="#suppress_issue">How can I suppress a specific analyzer warning?</a></li>
   <li><a href="#exclude_code">How can I selectively exclude code the analyzer examines?</a></li>
+  <li><a href="#run_on_single_file">How can I run the analyzer on a single file from the command line?</a></li>
 </ol>
 
 
 <h4 id="custom_assert" class="faq">Q: How do I tell the analyzer that I do not want the bug being
 reported here since my custom error handler will safely end the execution before
 the bug is reached?</h4>
 
 <img src="images/example_custom_assert.png" alt="example custom assert">

 #endif
 </pre>
 
 This usage is discouraged because it makes the code dead to the analyzer from 
 now on. Instead, we prefer that users file bugs against the analyzer when it flags 
 false positives.
 </p>
 
+<h4 id="run_on_single_file" class="faq">Q: How can I run the analyzer on a single file from command line?</h4>
+
+<p>The clang command line option <tt>--analyze</tt> enables usage on a single
+file:</p>
+
+<pre class="code_example">
+clang --analyze myfile.c
+</pre>
+
+<p>All usual clang flags may be used,
+e.g. a custom include directory may be specified:</p>
+
+<pre class="code_example">
+clang --analyze -Iinclude myotherfile.c
+</pre>
+
+<p>HTML reports can be generated by passing a command line flag:</p>
+
+<pre class="code_example">
+clang --analyze -Xclang -analyzer-output=html mythirdfile.c
+</pre>
+
+<p>By default, HTML reports are generated in a folder <tt>myfile.plist</tt>,
+where <tt>myfile</tt> is replaced with a filename of the analyzed translation
+unit.</p>
+
 </div>
 </div>
 </body>
 </html>
 

www/analyzer/scan-build.html

 <tt>clang</tt> or <tt>gcc</tt> (depending on the platform) to compile your 
 code and then executes the static analyzer to analyze your code.</p>
 
 <p>This &quot;poor man's interposition&quot; works amazingly well in many cases
 and falls down in others. Please consult the information on this page on making
 the best use of <b>scan-build</b>, which includes getting it to work when the
 aforementioned hack fails to work.</p>
 
+<h3>But what if I just need to analyze single file?</h3>
+
+<p>This FAQ
+<a href="/faq.html#run_on_single_file">answer</a>
+has all the details.<p>
+
 </td>
 <td style="padding-left:10px; text-align:center">
   <img src="images/scan_build_cmd.png" width="450px" alt="scan-build"><br>
   <a href="images/analyzer_html.png"><img src="images/analyzer_html.png" width="450px" alt="analyzer in browser"></a>
 <br><b>Viewing static analyzer results in a web browser</b>
 </td></tr></table>
 
 <h2>Contents</h2>