Severe error in re-deploying servlet - silly error - servlets

Question

I was trying to redeploy a servlet I had recently undeployed but kept getting a org.apache.catalina.LifecycleException. Tomcat wasn't able to load the context properly.
This is what triggered the search:
FAIL - Unable to delete [/var/lib/tomcat7/conf/Catalina/localhost/app.xml].
The continued presence of this file may cause problems.
Here are the errors from the log catalina.out, rearranged to fit the column:
WARNING: Calling stop() on failed component [{0}] to trigger clean-up
did not complete.
org.apache.catalina.LifecycleException:
An invalid Lifecycle transition was attempted ([after_stop]) for
component [org.apache.catalina.startup.FailedContext#13150fc] in state
[FAILED]
WARNING: Error while removing context [/app]
java.lang.ClassCastException:
org.apache.catalina.startup.FailedContext cannot be cast to
org.apache.catalina.core.StandardContext
Scrolling back up, I noticed a whole list of SEVERE errors, beginning with:
SEVERE: Parse error in context.xml for /app
org.xml.sax.SAXParseException;
systemId: file:/etc/tomcat7/Catalina/localhost/app.xml/;
lineNumber: 1;
columnNumber: 1;
Content is not allowed in prolog.
This is not related to Cannot Undeploy a web-app completely in Tomcat 7 or Installing JSTL results in org.xml.sax.SAXParseException: Content is not allowed in prolog, though I wasted quite some time looking through these. Everything seemed to be as it should be, so I was stumped. Eventually, I solved it myself. My answer is below.

Answer 1

It turns out that I had deployed
/path/to/servlet/web/
as the XML Configuration file instead of
/path/to/servlet/website.xml
as Tomcat had been expecting.
A quick check in the saved form content of my other browser revealed this kickself error, so I am posting a Q and A here in the hope that this could save someone some time.
Please be careful when deploying manually, people.