Add support for Central Package Management (CPM)

This means, if you manage common dependencies for many different projects,
you can leverage NuGet's Central Package Management (CPM) features to do
all of this from a single, central location.

Fixes #29.

Signed-off-by: klw1imb <wolfgang.klenk2@bosch.com>

Author: msz-bd

src/nuget-inspector/ProjectFileProcessor.cs

@@ -1,4 +1,5 @@
 using Microsoft.Build.Evaluation;
+using NuGet.Build.Tasks;
 using NuGet.Common;
 using NuGet.Frameworks;
 using NuGet.LibraryModel;
@@ -136,6 +137,52 @@ public virtual List<PackageReference> GetPackageReferences()
             globalProperties: properties,
             toolsVersion: null);
 
+        var globalPackageReferences = new List<PackageReference>();
+        var centralPackageVersions = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
+        var manageCentrally = project.GetPropertyValue("ManagePackageVersionsCentrally");
+        if (string.Equals(manageCentrally, "true", StringComparison.OrdinalIgnoreCase))
+        {
+            foreach (ProjectItem item in project.GetItems("GlobalPackageReference"))
+            {
+                var packageName = item.EvaluatedInclude;
+                var version = item.GetMetadataValue("Version");
+
+                if (!string.IsNullOrWhiteSpace(packageName) && !string.IsNullOrWhiteSpace(version))
+                {
+                    if (VersionRange.TryParse(version, out var versionRange))
+                    {
+                        var packageRef = new PackageReference(
+                            identity: new PackageIdentity(packageName, null),
+                            targetFramework: ProjectFramework,
+                            userInstalled: false,
+                            developmentDependency: false,
+                            requireReinstallation: false,
+                            allowedVersions: versionRange);
+
+                        globalPackageReferences.Add(packageRef);
+
+                        if (Config.TRACE)
+                            Console.WriteLine($"    Global package reference: {packageName} = {version}");
+                    }
+                }
+            }
+            references.AddRange(globalPackageReferences);
+
+            foreach (ProjectItem item in project.GetItems("PackageVersion"))
+            {
+                var packageName = item.EvaluatedInclude;
+                var version = item.GetMetadataValue("Version");
+
+                if (!string.IsNullOrWhiteSpace(packageName) && !string.IsNullOrWhiteSpace(version))
+                {
+                    centralPackageVersions[packageName] = version;
+
+                    if (Config.TRACE)
+                        Console.WriteLine($"    Central package version: {packageName} = {version}");
+                }
+            }
+        }
+
         foreach (ProjectItem reference in project.GetItems(itemType: "PackageReference"))
         {
             var name = reference.EvaluatedInclude;
@@ -185,15 +232,32 @@ public virtual List<PackageReference> GetPackageReferences()
                 continue;
             }
 
-            var version_metadata = reference.Metadata.FirstOrDefault(predicate: meta => meta.Name == "Version");
+            ProjectMetadata? version_metadata = reference.Metadata.FirstOrDefault(predicate: meta => meta.Name == "Version");
+            ProjectMetadata? versionOverride_metadata = reference.Metadata.FirstOrDefault(predicate: meta => meta.Name == "VersionOverride");
             VersionRange? version_range;
-            if (version_metadata is not null)
+            if (versionOverride_metadata is not null)
+            {
+                // VersionOverride takes precedence
+                VersionRange.TryParse(
+                    versionOverride_metadata.EvaluatedValue, 
+                    allowFloating: true, 
+                    out version_range);
+                if (Config.TRACE)
+                    Console.WriteLine($"    Applied VersionOverride for {name}: {versionOverride_metadata.EvaluatedValue}");
+            }
+            else if (version_metadata is not null)
             {
                 _ = VersionRange.TryParse(
                     value: version_metadata.EvaluatedValue,
                     allowFloating: true,
                     versionRange: out version_range);
             }
+            else if (centralPackageVersions.TryGetValue(name, out var centralVersionString))
+            {
+                VersionRange.TryParse(centralVersionString, out version_range);
+                if (Config.TRACE)
+                    Console.WriteLine($"    Applied central version for {name}: {centralVersionString}");
+            }
             else
             {
                 if (Config.TRACE)
@@ -211,31 +275,13 @@ public virtual List<PackageReference> GetPackageReferences()
                 // }
             }
 
-            PackageReference packref;
-
-            if (version_range == null)
-            {
-                if (Config.TRACE)
-                    Console.WriteLine($"    Project reference without version range: {name}");
-
-                packref = new PackageReference(
-                    identity: new PackageIdentity(id: name, version: null),
-                    targetFramework: ProjectFramework,
-                    userInstalled: false,
-                    developmentDependency: false,
-                    requireReinstallation: false,
-                    allowedVersions: VersionRange.All);
-            }
-            else
-            {
-                packref = new PackageReference(
-                    identity: new PackageIdentity(id: name, version: null),//(NuGetVersion?)version_range.MinVersion),
-                    targetFramework: ProjectFramework,
-                    userInstalled: false,
-                    developmentDependency: false,
-                    requireReinstallation: false,
-                    allowedVersions: version_range);
-            }
+            var packref = new PackageReference(
+                identity: new PackageIdentity(name, null),
+                targetFramework: ProjectFramework,
+                userInstalled: false,
+                developmentDependency: false,
+                requireReinstallation: false,
+                allowedVersions: version_range ?? VersionRange.All);
             references.Add(item: packref);
 
             if (Config.TRACE)