feat: build-on-node — git checkouts, remote image builds, image transport (#60)

Git-sourced deploys never materialized a checkout: sourcePath was
build_path resolved against the server cwd, so builds consumed the
backend's own directory. Remote placement could only run
registry-pulled images.

- internal/source: per-deployment checkout (init/fetch/checkout) at
  branch or commit; GIT_ASKPASS keeps tokens out of argv, .git/config,
  and the build context; dumb-transport and SHA-refusal fallbacks;
  build_path validated inside the checkout.
- BuildManager.PackageContext: produces the same tar context Build
  ships to the daemon — generated Dockerfile at tar root, .git
  excluded. Fixes nixpacks passing the Dockerfile path as content.
- Agent artifact endpoint: GET /api/agents/artifacts/:id streams
  build contexts and docker-save tarballs behind agent-token auth;
  hex-validated ids, per-deployment cleanup, boot-time purge.
- Agent commands: build_image (docker build -, --build-arg values via
  process env, not argv) and load_image (docker load for containr-*
  rollback tags no registry serves).
- Deployment flow: remote git builds package context → artifact →
  node docker-builds the deployment tag; remote rollbacks of local
  tags export via SaveImage → artifact → node docker-loads.

Verified end-to-end: agent-pinned git service built on the node
(build_image → create_container → deployed) and rollback shipped a
docker-save tarball (load_image → deployed). Artifact auth returns
401/404 correctly; workspaces and blobs are removed after deploy.

Authored By: TDvorak <[email protected]>

app/backend/internal/build/dockerfile.go

@@ -539,12 +539,16 @@ func createBuildContext(sourcePath, dockerfileContent string) (io.ReadCloser, er
 		return nil, err
 	}
 
-	// Add source files to tar
+	// Add source files to tar. The checkout's .git metadata is never build
+	// context — it bloats the tar and ships clone URLs to remote daemons.
 	err = filepath.Walk(sourcePath, func(file string, fi os.FileInfo, err error) error {
 		if err != nil {
 			return err
 		}
 		if fi.IsDir() {
+			if fi.Name() == ".git" {
+				return filepath.SkipDir
+			}
 			return nil
 		}
 

app/backend/internal/build/manager.go

@@ -3,6 +3,8 @@ package build
 import (
 	"context"
 	"fmt"
+	"io"
+	"os"
 	"path/filepath"
 	"time"
 
@@ -92,6 +94,75 @@ func (bm *BuildManager) Build(ctx context.Context, req *types.BuildRequest) (*ty
 	}
 }
 
+// PackageContext produces the same build-context tar Build would hand the
+// local daemon, without building it. Node agents download the tar and run
+// docker build themselves — the Dockerfile lands at the tar root.
+func (bm *BuildManager) PackageContext(ctx context.Context, req *types.BuildRequest) (io.ReadCloser, error) {
+	if req.BuildType == "" {
+		detectedType, err := bm.DetectBuildType(ctx, req.SourcePath)
+		if err != nil {
+			return nil, fmt.Errorf("failed to detect build type: %w", err)
+		}
+		req.BuildType = string(detectedType)
+	}
+
+	var dockerfileContent string
+	switch BuildType(req.BuildType) {
+	case BuildTypeDockerfile:
+		name, err := bm.dockerfileBuilder.DetectDockerfile(ctx, req.SourcePath)
+		if err != nil {
+			return nil, fmt.Errorf("failed to detect Dockerfile: %w", err)
+		}
+		path := filepath.Join(req.SourcePath, name)
+		if optimized, err := bm.dockerfileBuilder.OptimizeDockerfile(ctx, path); err == nil {
+			path = optimized
+		}
+		data, err := os.ReadFile(path)
+		if err != nil {
+			return nil, fmt.Errorf("failed to read Dockerfile: %w", err)
+		}
+		dockerfileContent = string(data)
+	case BuildTypeRailpack:
+		if err := bm.railpackBuilder.DetectRailpack(ctx, req.SourcePath); err != nil {
+			return nil, fmt.Errorf("Railpack cannot build this project: %w", err)
+		}
+		content, err := bm.railpackBuilder.generateDockerfile(ctx, req.SourcePath, &RailpackConfig{
+			BuildCmd: req.BuildCommand,
+			StartCmd: req.StartCommand,
+			Env:      req.Environment,
+		})
+		if err != nil {
+			return nil, fmt.Errorf("failed to generate Dockerfile with Railpack: %w", err)
+		}
+		dockerfileContent = content
+	case BuildTypeNixpacks:
+		plan, err := bm.nixpacksBuilder.GeneratePlan(ctx, req.SourcePath, &NixpacksConfig{
+			BuildCmd: req.BuildCommand,
+			StartCmd: req.StartCommand,
+			Env:      req.Environment,
+		})
+		if err != nil {
+			return nil, fmt.Errorf("failed to generate build plan: %w", err)
+		}
+		path, err := bm.nixpacksBuilder.generateDockerfile(plan)
+		if err != nil {
+			return nil, fmt.Errorf("failed to generate Dockerfile: %w", err)
+		}
+		defer os.Remove(path)
+		data, err := os.ReadFile(path)
+		if err != nil {
+			return nil, fmt.Errorf("failed to read generated Dockerfile: %w", err)
+		}
+		dockerfileContent = string(data)
+	case BuildTypeStatic:
+		dockerfileContent = staticDockerfile
+	default:
+		return nil, fmt.Errorf("unsupported build type for remote packaging: %s", req.BuildType)
+	}
+
+	return createBuildContext(req.SourcePath, dockerfileContent)
+}
+
 // buildPrebuilt handles prebuilt image deployments
 func (bm *BuildManager) buildPrebuilt(ctx context.Context, req *types.BuildRequest) (*types.BuildResponse, error) {
 	if req.PrebuiltImage == "" {

app/backend/internal/build/nixpacks.go

@@ -476,17 +476,22 @@ func (n *NixpacksBuilder) Build(ctx context.Context, req *types.BuildRequest) (*
 	}
 
 	// Create temporary Dockerfile
-	dockerfile, err := n.generateDockerfile(plan)
+	dockerfilePath, err := n.generateDockerfile(plan)
 	if err != nil {
 		return nil, fmt.Errorf("failed to generate Dockerfile: %w", err)
 	}
-	defer os.Remove(dockerfile)
+	defer os.Remove(dockerfilePath)
 
 	// Build Docker image
 	imageName := fmt.Sprintf("%s:%s", req.ImageName, req.ImageTag)
 
-	// Create build context tar
-	buildCtx, err := createBuildContext(req.SourcePath, dockerfile)
+	// Create build context tar — createBuildContext takes the Dockerfile
+	// contents, not its path.
+	dockerfileData, err := os.ReadFile(dockerfilePath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read generated Dockerfile: %w", err)
+	}
+	buildCtx, err := createBuildContext(req.SourcePath, string(dockerfileData))
 	if err != nil {
 		return nil, fmt.Errorf("failed to create build context: %w", err)
 	}