[SCM-801] Correct SCM URLs mangled in children

**[Caleb Cushing](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=xenoterracide)** opened **[SCM-801](https://issues.apache.org/jira/browse/SCM-801?redirect=false)** and commented

http://stackoverflow.com/a/26753032/206466

a lot of git repositories require the repository name to end it .git, only for a few services could this configuration ever be correct.

Because I know asking for the behavior to stop auto appending would break backwards compatibility, instead I'd like to see a field added that would allow us to override the behavior, so that we don't have to duplicate this section in every sub pom.

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**Issue Links:**
- [MPIR-234](https://issues.apache.org/jira/browse/MPIR-234) SCM-link in site of multimodule projects should not append module name by default (at least for git)
(_**"duplicates"**_)
- [MPIR-290](https://issues.apache.org/jira/browse/MPIR-290) improve git support: remove directory info (after '.git') for "git clone"

Start by reviewing the linked MPIR-234 and MPIR-290 issues, then trace the child SCM URL construction described in this issue. Determine where the module name is appended and how an override could preserve existing behavior. Done means Git repository URLs can opt out of the mangling without requiring duplicated configuration in every sub-POM.

Written by the indexing model from the issue text.