Path problems in git-for-windows bash

I am currently evaluating `mvnd` on Windows and found a strange path problem.

When executing `mvn clean verify` from CMD, PowerShell, or git-for-windows-bash, then I can build my sample project just fine.

When executing `mvnd clean verify` *from CMD or PowerShell*, then I still can build my sample project just fine (and, BTW, much faster).

But when ececuting `mvnd clean verify` *from git-for-windows-bash*, then apparently the buildnumber-maven-plugin is unable to find the git binary (which is in particularly weird as this is git-for-windows-bash actually!):

```
[ERROR] Failed to execute goal org.codehaus.mojo:buildnumber-maven-plugin:1.4:create (default) on project jakarta.ws.rs-api: Cannot get the branch information from the scm repository :
[ERROR] Exception while executing SCM command.: Error while executing command. Error while executing process. Cannot run program "git" (in directory "C:\Users\markus\git\jaxrs-api-master\jaxrs-api"): CreateProcess error=2, System cannot find the specified file
```

Is this a bug of `mvnd` or is there something the installation instructions are missing?

Reproduce `mvnd clean verify` from git-for-windows-bash and compare it with the working CMD and PowerShell runs. Start with mvnd's handling of the `git` executable and the buildnumber-maven-plugin error; done means the sample project builds successfully from that shell without the reported CreateProcess error.

Written by the indexing model from the issue text.