[MSITE-1016] site:stage should function without a URL specified in the POM

**[Claude Warren](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=claudenw)** opened **[MSITE-1016](https://issues.apache.org/jira/browse/MSITE-1016?redirect=false)** and commented

Note: actual version is 3.8.6

**Documentation states:**

> By default, the site will be staged in a directory `{}target/staging/{`}.

**Issue description:**

When I try to run site:stage without a site entry in the pom distrobutionManagement section I get an error that says the site entry must be specified.

> Specifying
> \
> \
> \staging\
> \
> \

Will yield an error that states the URL must be specified. Entering an invalid URL solves the problem.

> \
> > > \
> > > \staging\
> > > \invalid:url\
> > > \
> > > \

The above is literally the text in my pom file.

**Desired setup:**

I would like to see the URL be optional so that I can trigger the site:stage goal without having to specify the URL in the pom and without having to specify the stagingDirectory on the command line.

I would also like this better documented.

---

**Affects:** 3.20.0

**Issue Links:**
- [RAT-409](https://issues.apache.org/jira/browse/RAT-409) Site generation does not work without package
(_**"is caused by"**_)

Start with the site:stage goal and the POM distributionManagement site configuration described in the issue. Check how stagingDirectory and the site URL are required, then verify the documented default staging behavior. Done means site:stage works without a site URL or command-line stagingDirectory, and the documentation explains the setup.

Written by the indexing model from the issue text.