Default the manifest to index.mf and keep it out of its own listing (closes #100)

mfer gen now writes index.mf instead of .index.mf, the name fetch
requests and the README calls the standard filename. Given a
directory, check, freshen, list and export look only for index.mf;
.index.mf is no longer recognized. Because index.mf is not hidden, the
scanner now leaves the output file out of the listing by its path: gen
--force over an existing manifest no longer lists the old one, while a
file named index.mf in a subdirectory is still listed.

Model: opus-5-5

.gitignore

@@ -8,7 +8,7 @@ vendor.tzst
 modcache.tzst
 
 # Generated manifest files
-.index.mf
+/index.mf
 
 # Secrets
 .env

Dockerfile

@@ -75,5 +75,7 @@ RUN version="${VERSION:-$(git describe --tags --always)}"; \
 RUN ldd /mfer 2>&1 | grep -q 'not a dynamic executable'
 
 FROM scratch
+# scratch has no CA certificates; fetch needs them to verify HTTPS servers.
+COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
 COPY --from=builder /mfer /mfer
 ENTRYPOINT ["/mfer"]

README.md

@@ -36,12 +36,12 @@ Generate a manifest for a directory tree, verify it later, and fetch a published
 tree by URL:
 
 ```sh
-# Write .index.mf, a manifest of the files under the current directory.
+# Write index.mf, a manifest of the files under the current directory.
 bin/mfer gen .
 
 # Verify the files on disk against the manifest. Exits nonzero if any file
 # is missing or corrupted.
-bin/mfer check .index.mf
+bin/mfer check index.mf
 
 # Download and cryptographically verify a tree published over HTTP: mfer
 # fetches <url>/index.mf, then downloads every file it lists.

internal/cli/check.go

@@ -75,25 +75,22 @@ func safeRateUint64(rate float64) uint64 {
 	return uint64(rate)
 }
 
-// findManifest looks for a manifest file in the given directory.
+// findManifest returns the path of the manifest with the default name in
-// It checks for index.mf and .index.mf, returning the first one found.
+// dir, or an error if there is none.
 func findManifest(fs afero.Fs, dir string) (string, error) {
-	candidates := []string{"index.mf", ".index.mf"}
+	path := filepath.Join(dir, defaultManifestName)
-	for _, name := range candidates {
-		path := filepath.Join(dir, name)
 
 	exists, err := afero.Exists(fs, path)
 	if err != nil {
 		return "", err
 	}
 
-		if exists {
+	if !exists {
-			return path, nil
+		return "", fmt.Errorf("%w in %s (looked for %s)",
-		}
+			errNoManifestFound, dir, defaultManifestName)
 	}
 
-	return "", fmt.Errorf(
+	return path, nil
-		"%w in %s (looked for index.mf and .index.mf)", errNoManifestFound, dir)
 }
 
 // fetchManifestToTemp downloads a manifest URL to a temporary file and

internal/cli/entry_test.go

@@ -638,6 +638,43 @@ func TestGenerateFailsWithoutForceWhenOutputExists(t *testing.T) {
 	assert.Equal(t, "existing", string(content), "original file should be preserved")
 }
 
+// TestGenerateLeavesOutputOutOfListing overwrites an output file inside the
+// scanned tree with --force: the old file is not listed, while a file named
+// index.mf in a subdirectory still is.
+func TestGenerateLeavesOutputOutOfListing(t *testing.T) {
+	t.Parallel()
+
+	for name, output := range map[string]string{
+		"default name":                 "/testdir/index.mf",
+		"other name in a subdirectory": "/testdir/sub/listing.mf",
+	} {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			fs := afero.NewMemMapFs()
+			require.NoError(t, fs.MkdirAll("/testdir/sub", 0o755))
+			writeTestFile(t, fs, "/testdir/readme.txt", "hello")
+			writeTestFile(t, fs, "/testdir/sub/index.mf", "an ordinary file")
+			writeTestFile(t, fs, output, "previous manifest")
+
+			opts := testOpts([]string{
+				testApp, cmdGenerate, "-q", "--force", "-o", output, testDir,
+			}, fs)
+			require.Equal(t, 0, runCLI(opts), "stderr: %s", testStderr(t, opts))
+
+			manifest, err := mfer.NewManifestFromFile(fs, output)
+			require.NoError(t, err)
+
+			paths := make([]string, 0, len(manifest.Files()))
+			for _, f := range manifest.Files() {
+				paths = append(paths, f.GetPath())
+			}
+
+			assert.ElementsMatch(t, []string{"readme.txt", "sub/index.mf"}, paths)
+		})
+	}
+}
+
 func TestGenerateAtomicWriteUsesTemp(t *testing.T) {
 	t.Parallel()
 

internal/cli/errmsg_test.go

@@ -74,7 +74,7 @@ func TestNoManifestFoundMessage(t *testing.T) {
 	_, err := findManifest(afero.NewMemMapFs(), "/tmp/x")
 	require.ErrorIs(t, err, errNoManifestFound)
 	assert.EqualError(t, err,
-		"no manifest found in /tmp/x (looked for index.mf and .index.mf)")
+		"no manifest found in /tmp/x (looked for index.mf)")
 }
 
 func TestVerifyRequiredSignerMessages(t *testing.T) {

internal/cli/fetch.go

@@ -313,7 +313,7 @@ func checkNoSymlinks(p string) error {
 
 // resolveManifestURL takes a URL and returns the manifest URL.
 // If the URL already ends with .mf, it's returned as-is.
-// Otherwise, index.mf is appended.
+// Otherwise, the default manifest name is appended.
 func resolveManifestURL(inputURL string) (string, error) {
 	parsed, err := url.Parse(inputURL)
 	if err != nil {
@@ -330,8 +330,7 @@ func resolveManifestURL(inputURL string) (string, error) {
 		parsed.Path += "/"
 	}
 
-	// Append index.mf
+	parsed.Path += defaultManifestName
-	parsed.Path += "index.mf"
 
 	return parsed.String(), nil
 }

internal/cli/freshen.go

@@ -157,7 +157,7 @@ func (s *freshenScanner) walk(path string, info fs.FileInfo, walkErr error) erro
 	}
 
 	// Skip the manifest file itself
-	if relPath == s.manifestBase || relPath == "."+s.manifestBase {
+	if relPath == s.manifestBase {
 		return nil
 	}
 

internal/cli/gen.go

@@ -94,6 +94,7 @@ func (mfa *CLIApp) buildScannerOptions(ctx *cli.Context) *mfer.ScannerOptions {
 		FollowSymLinks:    ctx.Bool("follow-symlinks"),
 		IncludeTimestamps: ctx.Bool("include-timestamps"),
 		Fs:                mfa.Fs,
+		OutputPath:        ctx.String("output"),
 	}
 
 	// Set seed for deterministic UUID if provided

internal/cli/manifest_loader.go

@@ -65,7 +65,7 @@ func (mfa *CLIApp) openManifestReader(pathOrURL string) (io.ReadCloser, error) {
 }
 
 // resolveManifestArg resolves the manifest path from CLI arguments.
-// HTTP(S) URLs are returned as-is. Directories are searched for index.mf/.index.mf.
+// HTTP(S) URLs are returned as-is. Directories are searched for index.mf.
 // If no argument is given, the current directory is searched.
 func (mfa *CLIApp) resolveManifestArg(ctx *cli.Context) (string, error) {
 	if ctx.Args().Len() > 0 {

internal/cli/mfer.go

@@ -24,6 +24,11 @@ const (
 	flagProgress = "progress"
 
 	manifestArgsUsage = "[manifest file]"
+
+	// defaultManifestName is the filename gen writes by default, the one
+	// looked for when a command is given a directory, and the one fetch
+	// appends to a directory URL.
+	defaultManifestName = "index.mf"
 )
 
 // errUnknownCommand indicates an unrecognized command argument.
@@ -154,7 +159,7 @@ func (mfa *CLIApp) generateCommand() *cli.Command {
 			},
 			&cli.StringFlag{
 				Name:    "output",
-				Value:   "./.index.mf",
+				Value:   defaultManifestName,
 				Aliases: []string{"o"},
 				Usage:   "Specify output filename",
 			},

mfer/scanner.go

@@ -57,6 +57,10 @@ type ScannerOptions struct {
 	SigningOptions *SigningOptions
 	// Seed, if set, derives a deterministic UUID from this seed.
 	Seed string
+	// OutputPath, if set, is the file the manifest will be written to.
+	// Enumeration skips that one file, so a manifest written inside the
+	// scanned tree, or one it replaces there, is never listed.
+	OutputPath string
 }
 
 // FileEntry represents a file that has been enumerated.
@@ -75,6 +79,7 @@ type Scanner struct {
 	totalBytes FileSize // cached sum of all file sizes
 	options    *ScannerOptions
 	fs         afero.Fs
+	outputPath string // options.OutputPath made absolute; "" when unset
 }
 
 // NewScanner creates a new Scanner with default options.
@@ -93,11 +98,19 @@ func NewScannerWithOptions(opts *ScannerOptions) *Scanner {
 		fs = afero.NewOsFs()
 	}
 
-	return &Scanner{
+	s := &Scanner{
 		files:   make([]*FileEntry, 0),
 		options: opts,
 		fs:      fs,
 	}
+
+	if opts.OutputPath != "" {
+		// Abs fails only when there is no working directory, and then a
+		// relative output path could not be written either.
+		s.outputPath, _ = filepath.Abs(opts.OutputPath)
+	}
+
+	return s
 }
 
 // EnumerateFile adds a single file to the scanner, calling stat() to get metadata.
@@ -408,6 +421,11 @@ func (s *Scanner) enumerateFileWithInfo(
 	// Compute absolute path for file reading
 	absPath := filepath.Join(basePath, cleanPath)
 
+	// The manifest being written is not one of the files it lists.
+	if absPath == s.outputPath {
+		return nil
+	}
+
 	// Handle symlinks
 	if info.Mode()&fs.ModeSymlink != 0 {
 		if !s.options.FollowSymLinks {