Leave out of the build context what the app's .dockerignore names (closes #274)

Docker does not apply an app's `.dockerignore` to a build context sent as a tar, which is how upaas sends it, so every file in the clone, `.git/config` included, reached the build.

upaas now reads the ignore file as `docker build` does, with the `ignorefile` reader of `github.com/moby/patternmatcher`, and leaves those files out of the tar: an ignore file named after the Dockerfile and next to it, such as `Dockerfile.dockerignore`, otherwise `.dockerignore` at the root of the clone. The Dockerfile path is read as a path inside the clone, and the Dockerfile (or the lowercase `dockerfile` Docker builds when `Dockerfile` is missing) and the ignore file always stay in. An app without an ignore file builds as before.

Not handled: a Dockerfile that is a symlink to an ignored file fails the build.

Model: opus-5-5
Co-authored-by: clawbot <sneak+clawbot@sneak.cloud>

README.md

@@ -268,6 +268,12 @@ upaas fails the deploy instead of building. A Dockerfile that uses
 `RUN --network` needs Docker Engine 23.0 or later unless its `# syntax=` line
 names Dockerfile frontend 1.3 or later, such as `docker/dockerfile:1`.
 
+The build context leaves out the files the app's ignore file names, as
+`docker build` does: `<Dockerfile>.dockerignore` next to the app's Dockerfile if
+there is one, otherwise `.dockerignore` at the root of the repository. The
+Dockerfile and `.dockerignore` are always sent, even when the ignore file names
+them.
+
 Session secrets are automatically generated on first startup and persisted to
 `$UPAAS_DATA_DIR/session.key`.
 

TODO.md

@@ -20,6 +20,30 @@ regress.
 
 # Completed Steps
 
+- 2026-10-03: An app's build context leaves out the files its `.dockerignore`
+  names, such as `.git/config`, as `docker build` does; before, every file in
+  the clone was sent. An ignore file next to the Dockerfile,
+  `<Dockerfile>.dockerignore`, is read instead when there is one. The Dockerfile
+  and `.dockerignore` are always sent. An ignore file that cannot be read, or
+  holds a pattern Docker rejects, fails the build (#274).
+
+- 2026-10-03: `make test`, and so `docker build .`, fits a machine with 4 GiB of
+  memory: tests hash passwords with 1 MiB instead of upaasd's 64 MiB, so
+  `GOMAXPROCS=4 make test` peaks at about 1.4 GiB instead of 2.7 GiB. upaasd
+  still hashes with 64 MiB, and one test hashes and verifies a password at that
+  cost (#261).
+
+- 2026-10-02: In a window too narrow for the top bar, such as 390 px, the New
+  App and Logout buttons move to a second row instead of running into "by
+  @sneak"; the bar keeps a gap between its two sides at every width (#272).
+
+- 2026-10-02: App names may contain dots, such as `sneak.berlin`: lowercase
+  letters and numbers joined by single dots or by hyphens, 2 to 63 characters.
+  Docker accepts every such name in the image name `upaas-<name>`; a dot needs a
+  letter or number on both sides because Docker requires it. The new and edit
+  app forms check the same rule; browsers ignored their old pattern, which was
+  not a valid regular expression there (#260).
+
 - 2026-10-02: On the Applications list, a long repository URL now wraps within
   its column instead of making the table wider than its card, which cut off the
   Actions column and the Deploy buttons. In a window too narrow for the table,

go.mod

@@ -4,6 +4,7 @@ go 1.25
 
 require (
 	github.com/99designs/basicauth-go v0.0.0-20230316000542-bf6f9cbbf0f8
+	github.com/distribution/reference v0.6.0
 	github.com/docker/docker v27.3.1+incompatible
 	github.com/docker/go-connections v0.6.0
 	github.com/go-chi/chi/v5 v5.2.3
@@ -14,6 +15,7 @@ require (
 	github.com/joho/godotenv v1.5.1
 	github.com/mattn/go-sqlite3 v1.14.32
 	github.com/moby/buildkit v0.16.0
+	github.com/moby/patternmatcher v0.6.0
 	github.com/oklog/ulid/v2 v2.1.1
 	github.com/prometheus/client_golang v1.23.2
 	github.com/spf13/viper v1.21.0
@@ -39,7 +41,6 @@ require (
 	github.com/containerd/ttrpc v1.2.5 // indirect
 	github.com/containerd/typeurl/v2 v2.2.0 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
-	github.com/distribution/reference v0.6.0 // indirect
 	github.com/docker/go-units v0.5.0 // indirect
 	github.com/felixge/httpsnoop v1.0.4 // indirect
 	github.com/fsnotify/fsnotify v1.9.0 // indirect
@@ -60,7 +61,6 @@ require (
 	github.com/klauspost/compress v1.18.2 // indirect
 	github.com/moby/docker-image-spec v1.3.1 // indirect
 	github.com/moby/locker v1.0.1 // indirect
-	github.com/moby/patternmatcher v0.6.0 // indirect
 	github.com/moby/sys/sequential v0.6.0 // indirect
 	github.com/moby/sys/signal v0.7.1 // indirect
 	github.com/moby/sys/user v0.4.0 // indirect

internal/docker/buildcontext.go

@@ -0,0 +1,114 @@
+package docker
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/docker/docker/pkg/archive"
+	"github.com/moby/patternmatcher"
+	"github.com/moby/patternmatcher/ignorefile"
+)
+
+// defaultDockerfileName is the Dockerfile Docker builds when none is named.
+const defaultDockerfileName = "Dockerfile"
+
+// defaultDockerignoreName is the ignore file at the root of a build context,
+// read when the Dockerfile has no ignore file of its own.
+const defaultDockerignoreName = ".dockerignore"
+
+// tarBuildContext returns a tar of the build context in contextDir that leaves
+// out the files the app's ignore file names, as docker build does; Docker does
+// not apply the ignore file to a build context sent as a tar. dockerfile is
+// the path of the Dockerfile inside contextDir.
+func tarBuildContext(contextDir, dockerfile string) (io.ReadCloser, error) {
+	excludes, err := readDockerignore(contextDir, dockerfile)
+	if err != nil {
+		return nil, err
+	}
+
+	return archive.TarWithOptions(contextDir, &archive.TarOptions{
+		ExcludePatterns: excludes,
+	})
+}
+
+// readDockerignore returns the patterns of the files to leave out of the
+// build context in contextDir, read as docker build reads them for the
+// Dockerfile at dockerfile: from <dockerfile>.dockerignore next to the
+// Dockerfile if there is one, otherwise from .dockerignore at the root of the
+// context. Without either file there are no patterns.
+func readDockerignore(contextDir, dockerfile string) ([]string, error) {
+	// Docker reads the Dockerfile path as a path inside the build context:
+	// cleaned, with a leading / and any .. that would lead out of the context
+	// dropped, so ./Dockerfile and /Dockerfile both name the Dockerfile at the
+	// root.
+	dockerfile = strings.TrimPrefix(filepath.Join("/", dockerfile), "/")
+	if dockerfile == "" {
+		dockerfile = defaultDockerfileName
+	}
+
+	// Reading through os.Root keeps the read inside the build context, even
+	// when the ignore file is a symlink.
+	root, err := os.OpenRoot(contextDir)
+	if err != nil {
+		return nil, err
+	}
+
+	defer func() { _ = root.Close() }()
+
+	// When a Dockerfile named Dockerfile is missing, Docker builds a
+	// lowercase dockerfile in the same directory instead, and docker build
+	// then reads dockerfile.dockerignore as its ignore file.
+	if filepath.Base(dockerfile) == defaultDockerfileName {
+		lowercase := filepath.Join(filepath.Dir(dockerfile), "dockerfile")
+
+		_, dockerfileErr := root.Lstat(dockerfile)
+		_, lowercaseErr := root.Lstat(lowercase)
+
+		if errors.Is(dockerfileErr, fs.ErrNotExist) && lowercaseErr == nil {
+			dockerfile = lowercase
+		}
+	}
+
+	name := dockerfile + defaultDockerignoreName
+
+	file, err := root.Open(name)
+	if errors.Is(err, fs.ErrNotExist) {
+		name = defaultDockerignoreName
+		file, err = root.Open(name)
+	}
+
+	if errors.Is(err, fs.ErrNotExist) {
+		return nil, nil
+	}
+
+	if err != nil {
+		return nil, fmt.Errorf("failed to read %s: %w", name, err)
+	}
+
+	defer func() { _ = file.Close() }()
+
+	excludes, err := ignorefile.ReadAll(file)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read %s: %w", name, err)
+	}
+
+	// Like the docker command line, never leave out .dockerignore or the
+	// Dockerfile: Docker reads the Dockerfile from the context.
+	for _, keep := range []string{defaultDockerignoreName, filepath.ToSlash(dockerfile)} {
+		excluded, err := patternmatcher.MatchesOrParentMatches(keep, excludes)
+		if err != nil {
+			return nil, fmt.Errorf("invalid pattern in %s: %w", name, err)
+		}
+
+		if excluded {
+			excludes = append(excludes, "!"+keep)
+		}
+	}
+
+	return excludes, nil
+}

internal/docker/buildcontext_test.go

@@ -0,0 +1,326 @@
+package docker //nolint:testpackage // tests the unexported performBuild
+
+import (
+	"archive/tar"
+	"errors"
+	"io"
+	"log/slog"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"slices"
+	"strings"
+	"testing"
+
+	"github.com/docker/docker/client"
+)
+
+// File names used in more than one test build context, as constants to
+// satisfy the goconst linter.
+const (
+	testMainGo              = "main.go"
+	testSecretFile          = "secret.txt"
+	testDeployDockerfile    = "deploy/Dockerfile"
+	testLowercaseDockerfile = "dockerfile"
+)
+
+// TestPerformBuildFollowsDockerignore runs builds against a fake Docker API
+// and checks which files the build context sent to it holds.
+func TestPerformBuildFollowsDockerignore(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name       string
+		dockerfile string
+		files      map[string]string // path in the context: contents
+		want       []string          // files sent in the build context
+	}{
+		{
+			name:       "no ignore file",
+			dockerfile: defaultDockerfileName,
+			files:      map[string]string{defaultDockerfileName: "", testMainGo: ""},
+			want:       []string{defaultDockerfileName, testMainGo},
+		},
+		{
+			name:       "excludes and re-includes",
+			dockerfile: defaultDockerfileName,
+			files: map[string]string{
+				defaultDockerignoreName: "secret.txt\n*.md\n!README.md\n",
+				defaultDockerfileName:   "",
+				"NOTES.md":              "",
+				"README.md":             "",
+				testMainGo:              "",
+				testSecretFile:          "",
+			},
+			want: []string{
+				defaultDockerignoreName, defaultDockerfileName, "README.md", testMainGo,
+			},
+		},
+		{
+			name:       "keeps the Dockerfile and .dockerignore",
+			dockerfile: defaultDockerfileName,
+			files: map[string]string{
+				defaultDockerignoreName: "Dockerfile\n.dockerignore\nsecret.txt\n",
+				defaultDockerfileName:   "",
+				testMainGo:              "",
+				testSecretFile:          "",
+			},
+			want: []string{defaultDockerignoreName, defaultDockerfileName, testMainGo},
+		},
+		{
+			name:       "an ignore file next to the Dockerfile wins over .dockerignore",
+			dockerfile: testDeployDockerfile,
+			files: map[string]string{
+				defaultDockerignoreName:          "main.go\n",
+				testDeployDockerfile:             "",
+				"deploy/Dockerfile.dockerignore": "secret.txt\n",
+				testMainGo:                       "",
+				testSecretFile:                   "",
+			},
+			want: []string{
+				defaultDockerignoreName,
+				testDeployDockerfile,
+				"deploy/Dockerfile.dockerignore",
+				testMainGo,
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			contextDir := t.TempDir()
+			writeFiles(t, contextDir, tt.files)
+
+			got, err := buildContextFiles(t, contextDir, tt.dockerfile)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			if !slices.Equal(got, tt.want) {
+				t.Errorf("build context holds %q, want %q", got, tt.want)
+			}
+		})
+	}
+}
+
+// TestPerformBuildKeepsLowercaseDockerfile checks that when the Dockerfile
+// named Dockerfile is missing, the lowercase dockerfile Docker builds instead
+// stays in the build context, and its own ignore file is read.
+func TestPerformBuildKeepsLowercaseDockerfile(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name  string
+		files map[string]string // path in the context: contents
+		want  []string          // files sent in the build context
+	}{
+		{
+			name: "kept when the ignore file names it",
+			files: map[string]string{
+				defaultDockerignoreName: "*\n",
+				testLowercaseDockerfile: "",
+			},
+			want: []string{defaultDockerignoreName, testLowercaseDockerfile},
+		},
+		{
+			name: "its own ignore file wins over .dockerignore",
+			files: map[string]string{
+				defaultDockerignoreName:   "main.go\n",
+				testLowercaseDockerfile:   "",
+				"dockerfile.dockerignore": "secret.txt\n",
+				testMainGo:                "",
+				testSecretFile:            "",
+			},
+			want: []string{
+				defaultDockerignoreName,
+				testLowercaseDockerfile,
+				"dockerfile.dockerignore",
+				testMainGo,
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			contextDir := t.TempDir()
+			writeFiles(t, contextDir, tt.files)
+
+			got, err := buildContextFiles(t, contextDir, defaultDockerfileName)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			if !slices.Equal(got, tt.want) {
+				t.Errorf("build context holds %q, want %q", got, tt.want)
+			}
+		})
+	}
+}
+
+// TestPerformBuildReadsDockerfilePathInsideContext checks that ./Dockerfile
+// and /Dockerfile name the Dockerfile at the root of the context, as Docker
+// reads them, so an ignore file that names the Dockerfile does not leave it
+// out.
+func TestPerformBuildReadsDockerfilePathInsideContext(t *testing.T) {
+	t.Parallel()
+
+	for _, dockerfile := range []string{"./Dockerfile", "/Dockerfile"} {
+		t.Run(dockerfile, func(t *testing.T) {
+			t.Parallel()
+
+			contextDir := t.TempDir()
+			writeFiles(t, contextDir, map[string]string{
+				defaultDockerignoreName: "Dockerfile\nsecret.txt\n",
+				defaultDockerfileName:   "",
+				testMainGo:              "",
+				testSecretFile:          "",
+			})
+
+			got, err := buildContextFiles(t, contextDir, dockerfile)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			want := []string{defaultDockerignoreName, defaultDockerfileName, testMainGo}
+			if !slices.Equal(got, want) {
+				t.Errorf("build context holds %q, want %q", got, want)
+			}
+		})
+	}
+}
+
+// TestPerformBuildFailsOnMalformedDockerignore checks that a pattern the
+// docker command line would reject fails the build.
+func TestPerformBuildFailsOnMalformedDockerignore(t *testing.T) {
+	t.Parallel()
+
+	contextDir := t.TempDir()
+	writeFiles(t, contextDir, map[string]string{defaultDockerignoreName: "[\n"})
+
+	_, err := buildContextFiles(t, contextDir, defaultDockerfileName)
+
+	want := "failed to create build context: " +
+		"invalid pattern in .dockerignore: syntax error in pattern"
+	if err == nil || err.Error() != want {
+		t.Errorf("got error %v, want %q", err, want)
+	}
+}
+
+// TestPerformBuildFailsOnUnreadableDockerignore checks that an ignore file
+// that cannot be read, here because it is a directory, fails the build.
+func TestPerformBuildFailsOnUnreadableDockerignore(t *testing.T) {
+	t.Parallel()
+
+	contextDir := t.TempDir()
+
+	err := os.Mkdir(filepath.Join(contextDir, defaultDockerignoreName), 0o750)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = buildContextFiles(t, contextDir, defaultDockerfileName)
+
+	want := "failed to create build context: failed to read .dockerignore: "
+	if err == nil || !strings.HasPrefix(err.Error(), want) {
+		t.Errorf("got error %v, want one starting %q", err, want)
+	}
+}
+
+// writeFiles writes files, a map of paths inside dir to their contents,
+// creating the directories they are in.
+func writeFiles(t *testing.T, dir string, files map[string]string) {
+	t.Helper()
+
+	for name, contents := range files {
+		path := filepath.Join(dir, name)
+
+		err := os.MkdirAll(filepath.Dir(path), 0o750)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		err = os.WriteFile(path, []byte(contents), 0o600)
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+}
+
+// buildContextFiles runs a build of contextDir against a fake Docker API and
+// returns the names of the files in the build context sent to it, sorted.
+func buildContextFiles(t *testing.T, contextDir, dockerfile string) ([]string, error) {
+	t.Helper()
+
+	sent := make(chan []string, 1)
+
+	srv := httptest.NewServer(http.HandlerFunc(
+		func(w http.ResponseWriter, r *http.Request) {
+			switch {
+			case strings.HasSuffix(r.URL.Path, "/version"):
+				_, _ = w.Write([]byte(`{"Version":"27.3.1","ApiVersion":"1.47"}`))
+			case strings.HasSuffix(r.URL.Path, "/session"):
+				serveSession(t, w, r, make(chan string, 1))
+			case strings.HasSuffix(r.URL.Path, "/build"):
+				sent <- tarFileNames(t, r.Body)
+			default:
+				t.Errorf("unexpected request to %s", r.URL.Path)
+			}
+		},
+	))
+	t.Cleanup(srv.Close)
+
+	dockerAPI, err := client.NewClientWithOpts(
+		client.WithHost("tcp://" + srv.Listener.Addr().String()),
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	c := &Client{docker: dockerAPI, log: slog.Default()}
+
+	_, err = c.performBuild(t.Context(), BuildImageOptions{
+		ContextDir:     contextDir,
+		DockerfilePath: dockerfile,
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	return <-sent, nil
+}
+
+// tarFileNames returns the names of the regular files in the tar read from r,
+// sorted.
+func tarFileNames(t *testing.T, r io.Reader) []string {
+	t.Helper()
+
+	var names []string
+
+	reader := tar.NewReader(r)
+
+	for {
+		header, err := reader.Next()
+		if errors.Is(err, io.EOF) {
+			break
+		}
+
+		if err != nil {
+			t.Errorf("reading the build context: %v", err)
+
+			return nil
+		}
+
+		if header.Typeflag == tar.TypeReg {
+			names = append(names, header.Name)
+		}
+	}
+
+	slices.Sort(names)
+
+	return names
+}

internal/docker/client.go

@@ -25,7 +25,6 @@ import (
 	"github.com/docker/docker/api/types/network"
 	"github.com/docker/docker/api/types/versions"
 	"github.com/docker/docker/client"
-	"github.com/docker/docker/pkg/archive"
 	"github.com/docker/docker/pkg/jsonmessage"
 	"github.com/docker/docker/pkg/stdcopy"
 	"github.com/docker/go-connections/nat"
@@ -660,7 +659,7 @@ func (c *Client) performBuild(
 	}
 
 	// Create tar archive of build context
-	tarArchive, err := archive.TarWithOptions(opts.ContextDir, &archive.TarOptions{})
+	tarArchive, err := tarBuildContext(opts.ContextDir, opts.DockerfilePath)
 	if err != nil {
 		return "", fmt.Errorf("failed to create build context: %w", err)
 	}

internal/handlers/app_name_validation.go

@@ -13,12 +13,15 @@ const (
 	appNameMaxLength = 63
 )
 
-// validAppNameRe matches names containing only lowercase alphanumeric characters and
+// validAppNameRe matches runs of lowercase letters and digits joined by
-// hyphens, starting and ending with an alphanumeric character.
+// single dots or by hyphens, such as "my-app" or "sneak.berlin". Docker
-var validAppNameRe = regexp.MustCompile(`^[a-z0-9][a-z0-9-]*[a-z0-9]$`)
+// accepts every name it allows as the app's image name, upaas-<name>; a
+// dot needs a letter or digit on both sides because Docker requires it.
+// It also keeps the name from being "." or ".." or starting or ending
+// with a dot, so it is safe as a directory and file name. The pattern
+// attribute of the name field on the new and edit app forms is the same.
+var validAppNameRe = regexp.MustCompile(`^[a-z0-9]+((\.|-+)[a-z0-9]+)*$`)
 
-// validateAppName checks that the given app name is safe for use in Docker
-// container names, image tags, and file system paths.
 var (
 	errAppNameLength = errors.New(
 		"app name must be between " +
@@ -26,11 +29,14 @@ var (
 			strconv.Itoa(appNameMaxLength) + " characters",
 	)
 	errAppNamePattern = errors.New(
-		"app name must contain only lowercase letters, numbers, " +
+		"app name must contain only lowercase letters, numbers, hyphens, " +
-			"and hyphens, and must start and end with a letter or number",
+			"and dots, must start and end with a letter or number, " +
+			"and must have a letter or number on both sides of each dot",
 	)
 )
 
+// validateAppName checks that the given app name is safe for use in Docker
+// container names, image tags, and file system paths.
 func validateAppName(name string) error {
 	if len(name) < appNameMinLength || len(name) > appNameMaxLength {
 		return errAppNameLength

internal/handlers/app_name_validation_test.go

@@ -1,7 +1,16 @@
 package handlers //nolint:testpackage // testing unexported validateAppName
 
 import (
+	"bytes"
+	"strconv"
+	"strings"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"sneak.berlin/go/upaas/internal/models"
+	"sneak.berlin/go/upaas/templates"
 )
 
 func TestValidateAppName(t *testing.T) {
@@ -18,6 +27,10 @@ func TestValidateAppName(t *testing.T) {
 		{"valid two chars", "ab", false},
 		{"valid complex", "my-cool-app-v2", false},
 		{"valid all numbers", "123", false},
+		{"valid double hyphen", "my--app", false},
+		{"valid domain", "sneak.berlin", false},
+		{"valid two dots", "www.sneak.berlin", false},
+		{"valid dot and hyphen", "my-app.example.com", false},
 		{"empty", "", true},
 		{"single char", "a", true},
 		{"too long", "a" + string(make([]byte, 63)), true},
@@ -36,7 +49,12 @@ func TestValidateAppName(t *testing.T) {
 		{"starts with hyphen", "-myapp", true},
 		{"ends with hyphen", "myapp-", true},
 		{"underscore", "my_app", true},
-		{"dot", "my.app", true},
+		{"two dots in a row", "a..b", true},
+		{"starts with dot", ".a", true},
+		{"ends with dot", "a.", true},
+		{"only dots", "..", true},
+		{"hyphen before dot", "a-.b", true},
+		{"hyphen after dot", "a.-b", true},
 		{"slash", "my/app", true},
 		{"path traversal", "../etc/passwd", true},
 		{"special chars", "app@name!", true},
@@ -54,3 +72,42 @@ func TestValidateAppName(t *testing.T) {
 		})
 	}
 }
+
+func TestValidateAppNameErrorMentionsDots(t *testing.T) {
+	t.Parallel()
+
+	err := validateAppName("a..b")
+
+	require.ErrorIs(t, err, errAppNamePattern)
+	assert.Contains(t, err.Error(), "dots")
+}
+
+// TestAppFormsCheckAppNameLikeServer checks that the name field on the new
+// and edit app forms has the server's pattern and length limits, and that
+// its hint mentions dots.
+func TestAppFormsCheckAppNameLikeServer(t *testing.T) {
+	t.Parallel()
+
+	pattern := strings.TrimSuffix(strings.TrimPrefix(validAppNameRe.String(), "^"), "$")
+
+	pages := map[string]map[string]any{
+		"app_new.html":  {},
+		"app_edit.html": {dataKeyApp: &models.App{}},
+	}
+
+	for page, data := range pages {
+		var out bytes.Buffer
+
+		require.NoError(t, templates.GetParsed().ExecuteTemplate(&out, page, data))
+
+		// The name field and its hint, up to the end of their div.
+		_, field, found := strings.Cut(out.String(), `id="name"`)
+		require.True(t, found, page)
+
+		field, _, _ = strings.Cut(field, "</div>")
+		assert.Contains(t, field, `pattern="`+pattern+`"`, page)
+		assert.Contains(t, field, `minlength="`+strconv.Itoa(appNameMinLength)+`"`, page)
+		assert.Contains(t, field, `maxlength="`+strconv.Itoa(appNameMaxLength)+`"`, page)
+		assert.Contains(t, field, "hyphens, and dots", page)
+	}
+}

internal/handlers/dashboard_layout_test.go

@@ -52,3 +52,26 @@ func TestDashboardTableFitsCard(t *testing.T) {
 	assert.Contains(t, cellTag, "whitespace-normal")
 	assert.Contains(t, cellTag, "break-all")
 }
+
+// TestTopBarWrapsWhenNarrow checks that the top bar keeps a gap between the
+// µPaaS title and the New App and Logout buttons, and puts the buttons on a
+// second row in a window too narrow for one, instead of letting them meet.
+func TestTopBarWrapsWhenNarrow(t *testing.T) {
+	t.Parallel()
+
+	testCtx := setupTestHandlers(t)
+
+	request := httptest.NewRequestWithContext(t.Context(), http.MethodGet, "/", nil)
+	recorder := httptest.NewRecorder()
+
+	testCtx.handlers.HandleDashboard().ServeHTTP(recorder, request)
+
+	require.Equal(t, http.StatusOK, recorder.Code)
+
+	_, afterNav, found := strings.Cut(recorder.Body.String(), `<nav class="app-bar">`)
+	require.True(t, found, "dashboard has no top bar")
+
+	rowTag, _, _ := strings.Cut(strings.TrimSpace(afterNav), ">")
+	assert.Contains(t, rowTag, "flex-wrap")
+	assert.Contains(t, rowTag, "gap-")
+}

internal/handlers/handlers_test.go

@@ -109,6 +109,9 @@ func createAppServices(
 	})
 	require.NoError(t, authErr)
 
+	// 1 MiB per password hash instead of 64 MiB; see auth.Service.ArgonMemory.
+	authSvc.ArgonMemory = 1024
+
 	appSvc, appErr := app.New(fx.Lifecycle(nil), app.ServiceParams{
 		Logger:   logInstance,
 		Database: dbInstance,

internal/service/auth/auth.go

@@ -59,6 +59,13 @@ type ServiceParams struct {
 
 // Service provides authentication functionality.
 type Service struct {
+	// ArgonMemory is the memory each argon2id hash takes, in KiB. New sets
+	// argonMemory, 64 MiB, and upaasd never changes it. Tests lower it, since
+	// many 64 MiB hashes at once under the race detector need more memory
+	// than a 4 GiB build machine has. A hash verifies only with the value it
+	// was made with.
+	ArgonMemory uint32
+
 	log    *slog.Logger
 	db     *database.Database
 	store  *sessions.CookieStore
@@ -77,6 +84,7 @@ func New(_ fx.Lifecycle, params ServiceParams) (*Service, error) {
 	}
 
 	return &Service{
+		ArgonMemory: argonMemory,
 		log:         params.Logger.Get(),
 		db:          params.Database,
 		store:       store,
@@ -97,7 +105,7 @@ func (svc *Service) HashPassword(password string) (string, error) {
 		[]byte(password),
 		salt,
 		argonTime,
-		argonMemory,
+		svc.ArgonMemory,
 		argonThreads,
 		argonKeyLen,
 	)
@@ -132,7 +140,7 @@ func (svc *Service) VerifyPassword(hashedPassword, password string) bool {
 		[]byte(password),
 		salt,
 		argonTime,
-		argonMemory,
+		svc.ArgonMemory,
 		argonThreads,
 		argonKeyLen,
 	)

internal/service/auth/auth_test.go

@@ -65,6 +65,10 @@ func setupTestService(t *testing.T) (*auth.Service, func()) {
 	})
 	require.NoError(t, err)
 
+	// 1 MiB per hash instead of 64 MiB; see Service.ArgonMemory. The tests
+	// that use setupAuthService keep 64 MiB.
+	svc.ArgonMemory = 1024
+
 	// t.TempDir() automatically cleans up after test
 	cleanup := func() {}
 
@@ -237,6 +241,21 @@ func TestVerifyPassword(testingT *testing.T) {
 	})
 }
 
+// TestHashPasswordWithUpaasdMemory hashes and verifies a password with the
+// memory New sets, which upaasd uses. setupTestService lowers it.
+func TestHashPasswordWithUpaasdMemory(t *testing.T) {
+	t.Parallel()
+
+	svc := setupAuthService(t, false)
+	require.Equal(t, uint32(64*1024), svc.ArgonMemory)
+
+	hash, err := svc.HashPassword("correctpassword")
+	require.NoError(t, err)
+
+	assert.True(t, svc.VerifyPassword(hash, "correctpassword"))
+	assert.False(t, svc.VerifyPassword(hash, "wrongpassword"))
+}
+
 func TestIsSetupRequired(testingT *testing.T) {
 	testingT.Parallel()
 

internal/service/deploy/deploy_app_name_test.go

@@ -0,0 +1,121 @@
+package deploy_test
+
+import (
+	"context"
+	"log/slog"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"os"
+	"slices"
+	"strings"
+	"testing"
+
+	"github.com/distribution/reference"
+	"github.com/docker/docker/daemon/names"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"sneak.berlin/go/upaas/internal/database"
+	"sneak.berlin/go/upaas/internal/globals"
+	"sneak.berlin/go/upaas/internal/handlers"
+	"sneak.berlin/go/upaas/internal/logger"
+	"sneak.berlin/go/upaas/internal/models"
+	"sneak.berlin/go/upaas/internal/service/app"
+)
+
+// TestDeployAppWithDotInName creates an app named sneak.berlin through the
+// new app form, as a user does, then builds and deploys it against a fake
+// Docker API and checks that Docker accepts the names of the image it
+// builds and of the container it runs, using Docker's own rules for each.
+func TestDeployAppWithDotInName(t *testing.T) {
+	t.Parallel()
+
+	api := &fakeImageAPI{
+		images:   map[string][]string{},
+		shortSHA: "abc1234",
+		nextID:   "sha256:built",
+	}
+	svc, db := newImageTestService(t, api)
+	ctx := context.Background()
+
+	createdApp := createAppWithForm(t, db, "sneak.berlin")
+
+	deployment := models.NewDeployment(db)
+	deployment.AppID = createdApp.ID
+	require.NoError(t, deployment.Save(ctx))
+
+	imageID, err := svc.BuildImage(ctx, createdApp, deployment)
+	require.NoError(t, err)
+	require.NoError(t, svc.DeployContainer(ctx, createdApp, deployment, imageID))
+
+	images, _ := api.state()
+
+	api.mu.Lock()
+	containers := slices.Clone(api.containers)
+	api.mu.Unlock()
+
+	require.Equal(t, map[string][]string{
+		"sha256:built": {"upaas-sneak.berlin:abc1234"},
+	}, images)
+
+	_, err = reference.ParseNormalizedNamed("upaas-sneak.berlin:abc1234")
+	require.NoError(t, err)
+
+	require.Equal(t, []string{"upaas-sneak.berlin"}, containers)
+	assert.Regexp(t, names.RestrictedNamePattern, containers[0])
+
+	assert.DirExists(t, svc.GetBuildDirExported(createdApp.Name))
+}
+
+// createAppWithForm posts the new app form with the given name, which
+// checks the name as it does for a user, and returns the app it created.
+func createAppWithForm(
+	t *testing.T,
+	db *database.Database,
+	name string,
+) *models.App {
+	t.Helper()
+
+	log := logger.NewForTest(slog.New(slog.NewTextHandler(os.Stderr, nil)))
+
+	appSvc, err := app.New(nil, app.ServiceParams{Logger: log, Database: db})
+	require.NoError(t, err)
+
+	globalInstance, err := globals.New(nil)
+	require.NoError(t, err)
+
+	handlersInstance, err := handlers.New(nil, handlers.Params{
+		Logger:   log,
+		Globals:  globalInstance,
+		Database: db,
+		App:      appSvc,
+	})
+	require.NoError(t, err)
+
+	form := url.Values{
+		"name":     {name},
+		"repo_url": {"git@example.com:sneak/" + name + ".git"},
+	}
+	request := httptest.NewRequestWithContext(
+		t.Context(), http.MethodPost, "/apps", strings.NewReader(form.Encode()),
+	)
+	request.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+
+	recorder := httptest.NewRecorder()
+
+	handlersInstance.HandleAppCreate().ServeHTTP(recorder, request)
+
+	// The form redirects to the new app's page; it shows the form again,
+	// with the error, when it refuses the name.
+	require.Equal(t, http.StatusSeeOther, recorder.Code, recorder.Body.String())
+
+	appID, found := strings.CutPrefix(recorder.Header().Get("Location"), "/apps/")
+	require.True(t, found)
+
+	createdApp, err := models.FindApp(t.Context(), db, appID)
+	require.NoError(t, err)
+	require.NotNil(t, createdApp)
+
+	return createdApp
+}

internal/service/deploy/deploy_images_test.go

@@ -41,6 +41,7 @@ type fakeImageAPI struct {
 	nextID     string              // ID of the image the next build creates
 	removed    []string            // each tag or ID removed
 	forced     bool                // whether a removal was forced
+	containers []string            // name of each named container created
 }
 
 func (api *fakeImageAPI) ServeHTTP(w http.ResponseWriter, r *http.Request) {
@@ -67,6 +68,11 @@ func (api *fakeImageAPI) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	case strings.HasSuffix(r.URL.Path, "/version"):
 		_, _ = w.Write([]byte(`{"Version":"27.3.1","ApiVersion":"1.47"}`))
 	case strings.HasSuffix(r.URL.Path, "/containers/create"):
+		// The git clone's container has no name; the app's has.
+		if containerName := r.URL.Query().Get("name"); containerName != "" {
+			api.containers = append(api.containers, containerName)
+		}
+
 		_, _ = w.Write([]byte(`{"Id":"gitcontainer"}`))
 	case strings.HasSuffix(r.URL.Path, "/logs"):
 		writeCloneOutput(w, api.shortSHA)

internal/service/deploy/export_test.go

@@ -113,6 +113,16 @@ func (svc *Service) BuildImage(
 	return svc.buildImage(ctx, app, deployment)
 }
 
+// DeployContainer exposes deployContainerWithTimeout for testing.
+func (svc *Service) DeployContainer(
+	ctx context.Context,
+	app *models.App,
+	deployment *models.Deployment,
+	imageID docker.ImageID,
+) error {
+	return svc.deployContainerWithTimeout(ctx, app, deployment, imageID)
+}
+
 // BuildContainerOptionsExported exposes buildContainerOptions for testing.
 func (svc *Service) BuildContainerOptionsExported(
 	ctx context.Context,

templates/app_edit.html

@@ -30,10 +30,12 @@
                     name="name"
                     value="{{.App.Name}}"
                     required
-                    pattern="[a-z0-9-]+"
+                    minlength="2"
+                    maxlength="63"
+                    pattern="[a-z0-9]+((\.|-+)[a-z0-9]+)*"
                     class="input"
                 >
-                <p class="text-sm text-gray-500 mt-1">Lowercase letters, numbers, and hyphens only</p>
+                <p class="text-sm text-gray-500 mt-1">Lowercase letters, numbers, hyphens, and dots, such as my-app or example.com</p>
             </div>
 
             <div class="form-group">

templates/app_new.html

@@ -30,11 +30,13 @@
                     name="name"
                     value="{{.Name}}"
                     required
-                    pattern="[a-z0-9-]+"
+                    minlength="2"
+                    maxlength="63"
+                    pattern="[a-z0-9]+((\.|-+)[a-z0-9]+)*"
                     class="input"
                     placeholder="my-app"
                 >
-                <p class="text-sm text-gray-500 mt-1">Lowercase letters, numbers, and hyphens only</p>
+                <p class="text-sm text-gray-500 mt-1">Lowercase letters, numbers, hyphens, and dots, such as my-app or example.com</p>
             </div>
 
             <div class="form-group">

templates/base.html

@@ -26,7 +26,7 @@
 
 {{define "nav"}}
 <nav class="app-bar">
-    <div class="max-w-6xl mx-auto flex justify-between items-center">
+    <div class="max-w-6xl mx-auto flex flex-wrap justify-between items-center gap-3">
         <div class="flex items-center gap-3">
             <a href="/" class="text-xl font-medium text-gray-900 hover:text-primary-600 transition-colors">µPaaS</a>
             <span class="text-sm text-gray-500">by <a href="https://sneak.berlin" class="text-primary-600 hover:text-primary-800">@sneak</a></span>