Support generating portable Containerfiles. (#31)

README.md

@@ -79,12 +79,13 @@ Arguments:
 Options:
   -b, --base <base>    Flavor of the base image
   -t, --tag <tag>      Name for the built image [default: dotnet-app]
+  -a, --arch <arch>    Target architecture ('x64'/'arm64'/'s390x')
+                       The base image needs to support the selected architecture
   --push               After the build, push the image to the repository
+  --portable           Avoid using features that make the Containerfile not portable
+  --context <context>  Context directory for the build [default: .]
   --as-file <as-file>  Generates a Containerfile with the specified name
   --print              Print the Containerfile
-  --arch <arch>        Target architecture ('x64'/'arm64'/'s390x')
-                       The base image needs to support the selected architecture
-  --context <context>  Context directory for the build [default: .]
   --version            Show version information
   -?, -h, --help       Show help and usage information
 ```

src/build-image/BuildCommand.cs

@@ -13,28 +13,40 @@ public BuildCommand() :
         var asfileOption = new Option<string>( "--as-file", "Generates a Containerfile with the specified name");
         var printOption = new Option<bool>("--print", "Print the Containerfile") { Arity = ArgumentArity.Zero };
         var pushOption = new Option<bool>("--push", "After the build, push the image to the repository") { Arity = ArgumentArity.Zero };
-        var archOption = new Option<string>(new[] { "--arch" }, $"Target architecture ('x64'/'arm64'/'s390x')\nThe base image needs to support the selected architecture");
+        var archOption = new Option<string>(new[] { "--arch", "-a" }, $"Target architecture ('x64'/'arm64'/'s390x')\nThe base image needs to support the selected architecture");
         var contextOption = new Option<string>(new[] { "--context" }, getDefaultValue: () => ".", "Context directory for the build");
+        var portableOption = new Option<bool>("--portable", "Avoid using features that make the Containerfile not portable") { Arity = ArgumentArity.Zero };
 
+        var projectArg = new Argument<string>("PROJECT", getDefaultValue: () => ".", ".NET project to build");
+        Add(projectArg);
+
+        // note: order determines the help order
         Add(baseOption);
         Add(tagOption);
-        Add(pushOption);
-        Add(asfileOption);
-        Add(printOption);
         Add(archOption);
+
+        Add(pushOption);
+
+        Add(portableOption);
         Add(contextOption);
 
-        var projectArg = new Argument<string>("PROJECT", getDefaultValue: () => ".", ".NET project to build");
-        Add(projectArg);
+        Add(asfileOption);
+        Add(printOption);
 
         this.SetHandler((IConsole console,
-                         string? os, string tag, string? asfile, string project, bool push, bool print, string? arch, string? context) => Handle(console, os, tag, asfile, project, push, print, arch, context),
-                        baseOption, tagOption, asfileOption, projectArg, pushOption, printOption, archOption, contextOption);
+                         string? os, string tag, string? asfile, string project, bool push, bool print, string? arch, string? context, bool portable) => Handle(console, os, tag, asfile, project, push, print, arch, context, portable),
+                        baseOption, tagOption, asfileOption, projectArg, pushOption, printOption, archOption, contextOption, portableOption);
     }
 
-    public static int Handle(IConsole console, string? baseFlavor, string? tag, string? asfile, string project, bool push, bool print, string? arch, string? contextDir)
+    public static int Handle(IConsole console, string? baseFlavor, string? tag, string? asfile, string project, bool push, bool print, string? arch, string? contextDir, bool portable)
     {
-        ContainerEngine? containerEngine = ContainerEngine.TryCreate();
+        ContainerEngineFeature disabledFeatures = ContainerEngineFeature.None;
+        if (portable)
+        {
+            disabledFeatures = ContainerEngineFeature.All;
+        }
+
+        ContainerEngine? containerEngine = ContainerEngine.TryCreate(disabledFeatures);
         if (containerEngine is null && asfile is null)
         {
             console.Error.WriteLine("Install podman or docker to build images.");

src/build-image/ContainerEngine.cs

@@ -3,18 +3,33 @@
 using System.Diagnostics;
 using System.Text;
 
+[Flags]
+enum ContainerEngineFeature
+{
+    None = 0,
+    CacheMounts,
+    All = CacheMounts
+}
+
 class ContainerEngine
 {
     public const string Docker = "docker";
     public const string Podman = "podman";
 
     public string Command { get; }
     public Version Version { get; }
+    private ContainerEngineFeature _disabledFeatures;
+
+    private bool IsDisabled(ContainerEngineFeature feature) => (_disabledFeatures & ContainerEngineFeature.CacheMounts) != 0;
 
     public bool SupportsCacheMount
     {
         get
         {
+            if (IsDisabled(ContainerEngineFeature.CacheMounts))
+            {
+                return false;
+            }
             if (Command == Podman)
             {
                 return Version.Major >= 4;
@@ -31,13 +46,14 @@ public bool SupportsCacheMountSELinuxRelabling
         }
     }
 
-    private ContainerEngine(string command, Version version)
+    private ContainerEngine(string command, Version version, ContainerEngineFeature disabledFeatures)
     {
         Command = command;
         Version = version;
+        _disabledFeatures = disabledFeatures;
     }
 
-    public static ContainerEngine? TryCreate()
+    public static ContainerEngine? TryCreate(ContainerEngineFeature disableFeatures = ContainerEngineFeature.None)
     {
         string? command = null;
         Version? version = null;
@@ -67,7 +83,7 @@ private ContainerEngine(string command, Version version)
             return null;
         }
 
-        return new ContainerEngine(command, version ?? new Version());
+        return new ContainerEngine(command, version ?? new Version(), disableFeatures);
     }
 
     public bool TryBuild(IConsole console, string dockerFileName, string tag, string contextDir)
@@ -90,9 +106,9 @@ private ProcessCommand GetBuildCommand(string dockerFileName, string tag, string
             Arguments = { "build", "-f", dockerFileName, "-t", tag, contextDir }
         };
 
-        if (Command == Docker)
+        if (Command == Docker && !IsDisabled(ContainerEngineFeature.CacheMounts))
         {
-            // Support cache mounts.
+            // Enable cache mount support.
             command.EnvironmentVariables.Add(("DOCKER_BUILDKIT", "1"));
         }