[SCM-929] Release plugin does not work with central repository and always performs clone operation

**[Alexander Betaev](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=infestator)** opened **[SCM-929](https://issues.apache.org/jira/browse/SCM-929?redirect=false)** and commented

Plugin cannot work with repositories as if they were central ones. It pushes and updates data from central repo.
Please take a look at the patch here: SCM-631
Also look at MRELEA[SE-707](https://issues.apache.org/jira/browse/SE-707) issue. The patch from attachment enables usage of ${project.scm.developerConnection} var.

The attached patch makes plugin to work with repository as if it was central. The following arguments were used for manual testing:

```
mvn -f parent/pom.xml -DpushChanges=false -DscmPerformLocalUpdate=true -Dproject.scm.developerConnection=scm:hg:file://\${basedir}/../ release:prepare
mvn -f parent/pom.xml -DpushChanges=false -DscmPerformLocalUpdate=true -Dproject.scm.developerConnection=scm:hg:file://\${basedir}/../ release:perform
```

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**Attachments:**
- [maven-release-plugin.patch](https://issues.apache.org/jira/secure/attachment/12718064/maven-release-plugin.patch) (_10.57 kB_)
- [maven-release-plugin.patch](https://issues.apache.org/jira/secure/attachment/12718136/maven-release-plugin.patch) (_10.04 kB_)
- [maven-scm.patch](https://issues.apache.org/jira/secure/attachment/12718061/maven-scm.patch) (_6.62 kB_)
- [maven-test-project.tar.bz2](https://issues.apache.org/jira/secure/attachment/12718232/maven-test-project.tar.bz2) (_4.10 kB_)

Start by reviewing the attached maven-release-plugin.patch and maven-scm.patch, then reproduce the two Maven commands given in the issue using the supplied SCM settings. Compare the behavior with the referenced SCM-631 and MRELEASE-707 patches. Done means release:prepare and release:perform work with a central repository without always cloning and use the developer connection value as described.

Written by the indexing model from the issue text.