[MRELEASE-512] SCM information should be validated

**[Paul Benedict](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=paul4christ79)** opened **[MRELEASE-512](https://issues.apache.org/jira/browse/MRELEASE-512?redirect=false)** and commented

The plugin does not currently validate the SCM connection info. When preparing a release with invalid info, the project gets built, the transformed POM is committed, but the branching/tagging is doomed -- leaving the user having to perform a rollback.

I would like this plugin to automatically invoke `scm:validate`:
http://maven.apache.org/scm/maven-scm-plugin/validate-mojo.html

The earlier phase the better for validation. There's no point in compiling the project if the connection strings are wrong.

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**Affects:** 2.0-beta-8

**Issue Links:**
- [MRELEASE-986](https://issues.apache.org/jira/browse/MRELEASE-986) release:branch doesn't check if current project is located at it's scm location
(_**"is duplicated by"**_)
- [SCM-741](https://issues.apache.org/jira/browse/SCM-741) scm:validate for svn should offer a way to check the current directory actually matches what's declared in the pom

- [MRELEASE-484](https://issues.apache.org/jira/browse/MRELEASE-484) release:rollback fails after branch with NPE and complaint about missing scm URL

- [MRELEASE-494](https://issues.apache.org/jira/browse/MRELEASE-494) Should fail during release:prepare if scm:url doesn't match working copy

- [MRELEASE-445](https://issues.apache.org/jira/browse/MRELEASE-445) Validate tagBase before starting

8 votes, 10 watchers

Start with the release:prepare flow and the Maven SCM validate mojo described in the issue. Determine where SCM validation can run before project compilation and transformed-POM commits; done means invalid SCM connection information fails the release early and avoids those side effects.

Written by the indexing model from the issue text.