Keep the database files, logs and binaries out of the build context (closes #120)

The daemon's database is db.sqlite with its -wal and -shm files, which
the .db patterns in .dockerignore and .gitignore did not match, so a
database left in the clone shipped in the image's source archive.
.dockerignore now also excludes the logs and the .exe, .dll, .so and
.dylib files .gitignore already ignores. A test opens a database and
checks that .dockerignore has an any-depth pattern for each of its
files.

Model: opus-5-5

internal/database/dockerignore_internal_test.go

@@ -0,0 +1,61 @@
+package database
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"git.eeqj.de/sneak/routewatch/internal/config"
+	"git.eeqj.de/sneak/routewatch/internal/logger"
+)
+
+// TestDockerignoreExcludesDatabaseFiles checks that .dockerignore keeps the
+// database file, and the WAL and shared-memory files SQLite writes next to it,
+// out of the build context wherever they sit in the clone. The image ships the
+// whole build context as a source archive.
+func TestDockerignoreExcludesDatabaseFiles(t *testing.T) {
+	t.Parallel()
+
+	db, err := New(&config.Config{StateDir: t.TempDir()}, logger.New())
+	if err != nil {
+		t.Fatalf("failed to create database: %v", err)
+	}
+	defer func() { _ = db.Close() }()
+
+	data, err := os.ReadFile("../../.dockerignore")
+	if err != nil {
+		t.Fatalf("failed to read .dockerignore: %v", err)
+	}
+
+	// Docker reads `**/` as any number of directories and the rest of the
+	// pattern as filepath.Match does, so `**/` followed by a pattern that
+	// matches a file's name excludes that file at any depth.
+	var anyDepth []string
+
+	for line := range strings.Lines(string(data)) {
+		pattern, ok := strings.CutPrefix(strings.TrimSpace(line), "**/")
+		if ok {
+			anyDepth = append(anyDepth, pattern)
+		}
+	}
+
+	name := filepath.Base(db.path)
+
+	for _, file := range []string{name, name + "-wal", name + "-shm"} {
+		excluded := false
+
+		for _, pattern := range anyDepth {
+			matched, err := filepath.Match(pattern, file)
+			if err != nil {
+				t.Fatalf("bad .dockerignore pattern **/%s: %v", pattern, err)
+			}
+
+			excluded = excluded || matched
+		}
+
+		if !excluded {
+			t.Errorf(".dockerignore has no **/ pattern that excludes %s", file)
+		}
+	}
+}