Update-Pog: Skip frozen packages by default

app/Pog/Pog.psm1

@@ -154,10 +154,13 @@ function Update-Pog {
 			[switch]
 		$ManifestCheck,
 			[switch]
-		$Force
+		$Force,
+			### If passed, only update frozen packages, which are otherwise ignored.
+			[switch]
+		$Frozen
 	)
 
-	$ImportedPackages = Get-Pog $PackageName | ? {$_.Version -and $_.ManifestName}
+	$ImportedPackages = Get-Pog $PackageName | ? {$_.Version -and $_.ManifestName -and $_.UserManifest.Frozen -eq $Frozen}
 
 	$RepositoryPackageMap = @{}
 	$ImportedPackages | % ManifestName `

app/Pog/lib_compiled/Pog/src/Pog.PackageUserManifest.cs

@@ -7,6 +7,9 @@ namespace Pog;
 public record PackageUserManifest {
     public readonly string Path;
 
+    /// Indicates whether this package should be updated by `Update-Pog`.
+    public readonly bool Frozen = false;
+
     public PackageUserManifest(string userManifestPath) {
         InstrumentationCounter.UserManifestLoads.Increment();
 
@@ -23,6 +26,10 @@ public PackageUserManifest(string userManifestPath) {
         // parse the raw manifest into properties on this object
         var parser = new HashtableParser(raw);
 
+        if (parser.ParseScalar<bool>("Frozen", false) is {} frozen) {
+            Frozen = frozen;
+        }
+
         if (parser.HasIssues) {
             throw new InvalidPackageManifestStructureException(userManifestPath, parser.Issues);
         }