Add URLs to add, and a migrate command that deletes originals

add now downloads http(s) URLs (with a Chrome user agent) through a
private temporary file, and treats ".", ".." and "/" as "this folder's
contents" so the destination folder is no longer dropped for "..".

migrate is add followed by deleting each original and any directories
left empty. It asks on the terminal before overwriting anything already
in the vault, refusing when there is no terminal, unless --yes is given.

Adding or migrating a directory skips the vault and key file if they
live inside it, so migrate can never ingest or delete them.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

vault_test.go

@@ -9,9 +9,12 @@ import (
 	"crypto/rand"
 	"io"
 	"io/fs"
+	"net/http"
+	"net/http/httptest"
 	"os"
 	"os/exec"
 	"path/filepath"
+	"slices"
 	"testing"
 	"time"
 )
@@ -295,3 +298,78 @@ func TestFiller(t *testing.T) {
 		t.Fatalf("filler objects total %d, largest %d", total, largest)
 	}
 }
+
+// TestAddTree migrates "." holding the vault and key: structure is kept,
+// originals and emptied directories go, the vault and key are left alone.
+// A URL download is then added under a folder.
+func TestAddTree(t *testing.T) {
+	dir := t.TempDir()
+	keyPath := filepath.Join(dir, "key")
+	if err := writeKeyFile(keyPath, "pass", ""); err != nil {
+		t.Fatal(err)
+	}
+	if err := initStore(filepath.Join(dir, "store"), 0); err != nil {
+		t.Fatal(err)
+	}
+	s := newTestStore(t, keyPath, "pass")
+	os.MkdirAll(filepath.Join(dir, "a", "b"), 0o755)
+	os.WriteFile(filepath.Join(dir, "x"), []byte("x"), 0o600)
+	os.WriteFile(filepath.Join(dir, "a", "b", "y"), []byte("y"), 0o600)
+	t.Chdir(dir)
+
+	var skip []os.FileInfo
+	for _, p := range []string{"store", "key"} {
+		fi, _ := os.Stat(p)
+		skip = append(skip, fi)
+	}
+	cat, _ := s.catalogue()
+	if err := addPath(s, cat, "x", "d", false, skip, nil); err != nil {
+		t.Fatal(err)
+	}
+	// Migrating over d/x must ask first, and a no must leave everything.
+	var asked []string
+	no := func(names []string) bool { asked = names; return false }
+	if err := addPath(s, cat, ".", "d", true, skip, no); err == nil || !slices.Equal(asked, []string{"d/x"}) {
+		t.Fatalf("migrate over d/x: err %v, asked %v", err, asked)
+	}
+	if _, err := os.Stat("x"); err != nil || len(cat) != 1 {
+		t.Fatalf("declined migrate changed things: %v, %d stored", err, len(cat))
+	}
+	if err := addPath(s, cat, ".", "d", true, skip, func([]string) bool { return true }); err != nil {
+		t.Fatal(err)
+	}
+	var got []string
+	for name := range cat {
+		got = append(got, name)
+	}
+	slices.Sort(got)
+	if !slices.Equal(got, []string{"d/a/b/y", "d/x"}) {
+		t.Fatalf("stored %v", got)
+	}
+	var left []string
+	entries, _ := os.ReadDir(".")
+	for _, e := range entries {
+		left = append(left, e.Name())
+	}
+	if !slices.Equal(left, []string{"key", "store"}) {
+		t.Fatalf("left behind %v", left)
+	}
+
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.UserAgent() != chromeUA {
+			http.Error(w, "bad agent", http.StatusForbidden)
+			return
+		}
+		io.WriteString(w, "body")
+	}))
+	defer srv.Close()
+	if err := addURL(s, cat, srv.URL+"/files/page.html", "web"); err != nil {
+		t.Fatal(err)
+	}
+	if err := s.get("web/page.html", "out"); err != nil {
+		t.Fatal(err)
+	}
+	if b, _ := os.ReadFile("out"); string(b) != "body" {
+		t.Fatalf("downloaded %q", b)
+	}
+}