Investigate issue when NuGet updater pins a transitive dependency

Scenario seen in an internal conversation.

A transitive dependency needed to be pinned to a specific version in `project.csproj`, but the repo was using Central Package Management and the corresponding entry in `Directory.Packages.props` was missing.

E.g., the following change was made in `project.csproj`

``` diff
...
+
...
```

However the following change was expected, but not made in `Directory.Packages.props

``` diff
...
+
...
```

Start by examining the NuGet updater behavior for a project using project.csproj and Central Package Management through Directory.Packages.props. Reproduce the transitive dependency pinning scenario and compare the generated changes; done means the package version entry is placed in Directory.Packages.props rather than only in project.csproj.

Written by the indexing model from the issue text.