Disable the deprecated gomodguard linter (closes #116)

golangci-lint v2.12 deprecates gomodguard in favour of gomodguard_v2.
With `default: all` both ran, and every lint run printed the
deprecation warning. Disable the old name, the same way wsl is
disabled for wsl_v5; gomodguard_v2 stays enabled. The old linter had
no settings here, so there is nothing to carry over.

Model: opus-5-5

.golangci.yml

@@ -16,6 +16,7 @@ linters:
     - depguard         # Dependency allow/block lists
     - godot            # Requires comments to end with periods
     - wsl              # Deprecated, replaced by wsl_v5
+    - gomodguard       # Deprecated, replaced by gomodguard_v2
     - wrapcheck        # Too verbose for internal packages
     - varnamelen       # Short names like db, id are idiomatic Go
   settings:

Dockerfile

@@ -14,7 +14,9 @@ RUN touch mfer/mf.pb.go
 # Go half of fmt-check only: this image has no node, so no prettier. The
 # markdown half runs in the mdfmt stage below.
 RUN make fmt-check-go
-RUN make lint
+# The linter directly, not `make lint`: script/lint builds this stage, and
+# there is no docker inside this build.
+RUN golangci-lint run --config .golangci.yml ./...
 
 # Markdown/JSON format stage — prettier needs node, which the Go images
 # do not have. node:22.17.0-bookworm-slim (2026-08-09); ships node
@@ -67,7 +69,10 @@ RUN version="${VERSION:-$(git describe --tags --always)}"; \
         exit 1; \
     fi; \
     cd cmd/mfer && \
-    go build -tags urfave_cli_no_docs -ldflags "-X main.Gitrev=$version" -o /mfer .
+    CGO_ENABLED=0 go build -tags urfave_cli_no_docs -ldflags "-X main.Gitrev=$version" -o /mfer .
+
+# Fail unless /mfer is statically linked: scratch has no C library to run it.
+RUN ldd /mfer 2>&1 | grep -q 'not a dynamic executable'
 
 FROM scratch
 COPY --from=builder /mfer /mfer

Makefile

@@ -58,9 +58,6 @@ fmt-check-md:
 hooks:
 	@script/install-precommit
 
-devprereqs:
-	which golangci-lint || go install -v github.com/golangci/golangci-lint/v2/cmd/golangci-lint@v2.12.2
-
 mfer/mf.pb.go: mfer/mf.proto
 	cd mfer && go generate .
 

README.md

@@ -1,12 +1,12 @@
 # mfer
 
-[mfer](https://git.eeqj.de/sneak/mfer) is a reference implementation library and
-thin wrapper command-line utility written in [Go](https://golang.org) and first
-published in 2022 under the [WTFPL](https://wtfpl.net) (public domain) license.
-It specifies and generates `.mf` manifest files over a directory tree of files
-to encapsulate metadata about them (such as cryptographic checksums or
-signatures over same) to aid in archiving, downloading, and streaming, or
-mirroring. The manifest files' data is serialized with Google's
+[mfer](https://git.eeqj.de/sneak/mfer) is a [WTFPL](https://wtfpl.net)-licensed
+(public domain) [Go](https://golang.org) library and command-line tool by
+[@sneak](https://sneak.berlin) that specifies and generates `.mf` manifest files
+over a directory tree to encapsulate metadata about the files — such as
+cryptographic checksums and signatures over same — to aid in archiving,
+downloading, streaming, and mirroring. It was first published in 2022. The
+manifest files' data is serialized with Google's
 [protobuf serialization format](https://developers.google.com/protocol-buffers).
 The structure of these files can be found
 [in the format specification](https://git.eeqj.de/sneak/mfer/src/branch/main/mfer/mf.proto)
@@ -21,6 +21,36 @@ This project was started by [@sneak](https://sneak.berlin) to scratch an itch in
 as a de-facto standard and be incorporated into other software. A compatible
 javascript library is planned.
 
+# Getting Started
+
+`mfer` builds from source with a Go 1.23+ toolchain. The generated protobuf code
+is committed, so no `protoc` toolchain is required:
+
+```sh
+git clone https://git.eeqj.de/sneak/mfer.git
+cd mfer
+go build -o bin/mfer ./cmd/mfer
+```
+
+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.
+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
+
+# Download and cryptographically verify a tree published over HTTP: mfer
+# fetches <url>/index.mf, then downloads every file it lists.
+bin/mfer fetch https://example.com/tree/
+```
+
+Run `bin/mfer help` for the full command list, or `bin/mfer <command> --help`
+for a single command's options.
+
 # Build Status
 
 CI runs `script/cibuild`, which builds the Docker image with `--no-cache`, so
@@ -35,9 +65,9 @@ standard: normalized scripts in `script/` are the entrypoints for the
 development workflow, and the Makefile targets are thin shims that call them. We
 provide:
 
-- `script/bootstrap` — install all dependencies (Go, golangci-lint, Go module
-  download, and node/yarn plus the prettier version pinned in
-  `package.json`/`yarn.lock`), idempotently
+- `script/bootstrap` — install all dependencies (Go, Go module download, and
+  node/yarn plus the prettier version pinned in `package.json`/`yarn.lock`),
+  idempotently; golangci-lint is not installed, it runs only in Docker
 - `script/setup` — make a fresh clone ready for development: runs
   `script/bootstrap`, then `script/install-precommit`
 - `script/projectname` — output the project name (`mfer`); used by other scripts
@@ -47,9 +77,11 @@ provide:
 - `script/fuzz` — fuzz the manifest parser for one minute; run by hand
   (`make fuzz`), never by CI, while `script/test` runs its committed seed corpus
   as ordinary tests
-- `script/lint` — run `golangci-lint` and verify `gofmt` cleanliness
-- `script/fmt` — format all code and docs (writes): `gofumpt`,
-  `golangci-lint run --fix`, and `script/prettier --write`
+- `script/lint` — run `golangci-lint` in Docker: builds only the `lint` stage of
+  the `Dockerfile` (the Go format check, then the linter), uncached so it runs
+  every time, then removes the image
+- `script/fmt` — format all code and docs (writes): `gofumpt` and
+  `script/prettier --write`
 - `script/prettier` — run prettier over the repository's canonical file set
   (Markdown and JSON, minus `.prettierignore`) in the given mode, `--write` or
   `--check`; the single definition of that file set, so `script/fmt` and
@@ -75,17 +107,18 @@ yet. Primary development happens on a privately-run Gitea instance at
 [tracked there](https://git.eeqj.de/sneak/mfer/issues).
 
 Changes must always be formatted with a standard `go fmt`, syntactically valid,
-and must pass the linting defined in the repository (presently only the
-`golangci-lint` defaults), which can be run with a `make lint`. The `main`
-branch is protected and all changes must be made via
-[pull requests](https://git.eeqj.de/sneak/mfer/pulls) and pass CI to be merged.
-Any changes submitted to this project must also be
+and must pass the linting defined in the repository's `.golangci.yml`, which
+`make lint` runs in Docker. The `main` branch is protected and all changes must
+be made via [pull requests](https://git.eeqj.de/sneak/mfer/pulls) and pass CI to
+be merged. Any changes submitted to this project must also be
 [WTFPL-licensed](https://wtfpl.net) to be considered.
 
 See [`REPO_POLICIES.md`](REPO_POLICIES.md) for detailed coding standards,
 tooling requirements, and workflow conventions.
 
-# Problem Statement
+# Rationale
+
+## The problem
 
 Given a plain URL, there is no standard way to safely and programmatically
 download everything "under" that URL path. `wget -r` can traverse directory
@@ -109,7 +142,7 @@ Real issues I face:
 - when I download a large file via HTTP, I have no way of knowing if the file
   content is what it's supposed to be
 
-# Proposed Solution
+## The solution
 
 A standard, a manifest file format, and a tool for generating same.
 
@@ -141,6 +174,28 @@ The manifest file would do several important things:
     - maybe a bittorrent chunklist for torrent client compatibility? perhaps a
       top-level infohash for the whole manifest?
 
+# Design
+
+The repository is split into a reusable library and a thin command-line wrapper
+around it.
+
+- `mfer/` is the reusable library and the heart of the project: it defines the
+  manifest format and implements building, scanning, checking, serialization,
+  and signing. The protobuf schema is `mfer/mf.proto`, and the generated code it
+  produces (`mfer/mf.pb.go`) is committed alongside it so the library builds
+  with `go get` and needs no `protoc` toolchain.
+- `internal/cli/` holds the command implementations — `generate` (alias `gen`),
+  `check`, `freshen`, `export`, `list` (alias `ls`), `fetch`, and `version` —
+  that wire the library to the command-line interface.
+- `internal/log/` provides the logging used by the commands and the library.
+- `internal/bork/` provides the error the library returns when a manifest's
+  decompressed contents are not the size the manifest records.
+- `cmd/mfer/` is the entrypoint: its `main` package runs `internal/cli` and
+  exits with the status it returns.
+
+Everything under `internal/` is private to this repository; only the `mfer/`
+package is intended for import by other software.
+
 # Design Goals
 
 - Replace SHASUMS/SHASUMS.asc files
@@ -274,9 +329,9 @@ Open work, open design questions included, is tracked in this repo's issues:
 - Issues:
   [https://git.eeqj.de/sneak/mfer/issues](https://git.eeqj.de/sneak/mfer/issues)
 
-# Authors
+# Author
 
-- [@sneak &lt;sneak@sneak.berlin&gt;](mailto:sneak@sneak.berlin)
+- [@sneak](https://sneak.berlin)
 
 # License
 

mfer/gpg_test.go

@@ -10,6 +10,7 @@ import (
 	"path/filepath"
 	"strconv"
 	"strings"
+	"syscall"
 	"testing"
 	"time"
 
@@ -425,36 +426,51 @@ func TestGPGTimeoutKillsGPG(t *testing.T) {
 	assert.Contains(t, err.Error(), "gpg sign failed: gpg timed out")
 }
 
-// TestGPGTimeoutWhenChildHoldsOutput uses a fake gpg that runs sleep as a
+// TestGPGCancelWhenChildHoldsOutput uses a fake gpg that runs sleep as a
 // child instead of exec-ing it, the way a wrapper script around the real
 // gpg might. Killing the fake gpg leaves sleep holding its stdout and
-// stderr open; the call must still return shortly after the deadline
-// instead of waiting for sleep to exit. The fake gpg writes the process ID
-// of sleep to a file so that the test can kill it before returning.
-func TestGPGTimeoutWhenChildHoldsOutput(t *testing.T) {
-	pidFile := filepath.Join(t.TempDir(), "sleep.pid")
+// stderr open; the call must still return once ctx ends instead of waiting
+// for sleep to exit. The fake gpg writes the process ID of sleep to a named
+// pipe; the test ends ctx only after reading it, so sleep is running by
+// then, and kills sleep before returning.
+func TestGPGCancelWhenChildHoldsOutput(t *testing.T) {
+	pidPipe := filepath.Join(t.TempDir(), "sleep.pid")
+	require.NoError(t, syscall.Mkfifo(pidPipe, 0o600))
+	// sleep outlasts the 10 s wait below, so a call that waits for it fails.
 	t.Setenv("PATH", fakeGPGPath(t,
-		"#!/bin/sh\nsleep 3 &\necho $! >'"+pidFile+"'\nwait\n"))
-	t.Cleanup(func() {
-		pid, err := os.ReadFile(pidFile) //nolint:gosec // G304: path inside t.TempDir()
-		require.NoError(t, err)
+		"#!/bin/sh\nsleep 60 &\necho $! >'"+pidPipe+"'\nwait\n"))
 
-		n, err := strconv.Atoi(strings.TrimSpace(string(pid)))
-		require.NoError(t, err)
-
-		sleep, err := os.FindProcess(n)
-		require.NoError(t, err)
-		require.NoError(t, sleep.Kill())
-	})
-
-	ctx, cancel := context.WithTimeout(context.Background(), 100*time.Millisecond)
+	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
 
-	start := time.Now()
-	_, err := gpgSign(ctx, []byte("data"), GPGKeyID("any"))
-	require.ErrorIs(t, err, context.DeadlineExceeded)
-	assert.Less(t, time.Since(start), 3*time.Second,
-		"the call waited for the child holding gpg's output to exit")
+	signErr := make(chan error, 1)
+
+	go func() {
+		_, err := gpgSign(ctx, []byte("data"), GPGKeyID("any"))
+		signErr <- err
+	}()
+
+	pid, err := os.ReadFile(pidPipe) //nolint:gosec // G304: path inside t.TempDir()
+	require.NoError(t, err)
+
+	n, err := strconv.Atoi(strings.TrimSpace(string(pid)))
+	require.NoError(t, err)
+
+	sleep, err := os.FindProcess(n)
+	require.NoError(t, err)
+	t.Cleanup(func() { require.NoError(t, sleep.Kill()) })
+
+	cancel()
+
+	// The call should return about gpgWaitDelay (one second) after the
+	// cancel. 10 s is far above that and well under the 30 s test timeout,
+	// which would abort the whole package before the cleanup kills sleep.
+	select {
+	case err := <-signErr:
+		require.ErrorIs(t, err, context.Canceled)
+	case <-time.After(10 * time.Second):
+		t.Fatal("the call waited for the child holding gpg's output to exit")
+	}
 }
 
 // TestBuildPassesContextToSigning checks that a caller can cancel the gpg

mfer/scanner_test.go

@@ -304,46 +304,19 @@ func TestScannerEnumerateFS(t *testing.T) {
 func TestSendEnumerateStatusNonBlocking(t *testing.T) {
 	t.Parallel()
 
-	// Channel with no buffer - send should not block
+	// Nobody receives, so a blocking send would hang the test into its timeout.
 	ch := make(chan EnumerateStatus)
 
-	// This should not block
-	done := make(chan bool)
-
-	go func() {
-		sendEnumerateStatus(ch, EnumerateStatus{FilesFound: 1})
-
-		done <- true
-	}()
-
-	select {
-	case <-done:
-		// Success - did not block
-	case <-time.After(100 * time.Millisecond):
-		t.Fatal("sendEnumerateStatus blocked on full channel")
-	}
+	sendEnumerateStatus(ch, EnumerateStatus{FilesFound: 1})
 }
 
 func TestSendScanStatusNonBlocking(t *testing.T) {
 	t.Parallel()
 
-	// Channel with no buffer - send should not block
+	// Nobody receives, so a blocking send would hang the test into its timeout.
 	ch := make(chan ScanStatus)
 
-	done := make(chan bool)
-
-	go func() {
-		sendScanStatus(ch, ScanStatus{ScannedFiles: 1})
-
-		done <- true
-	}()
-
-	select {
-	case <-done:
-		// Success - did not block
-	case <-time.After(100 * time.Millisecond):
-		t.Fatal("sendScanStatus blocked on full channel")
-	}
+	sendScanStatus(ch, ScanStatus{ScannedFiles: 1})
 }
 
 func TestSendStatusNilChannel(t *testing.T) {

script/bootstrap

@@ -140,12 +140,7 @@ main() {
 
     # ---- Go repos ----
     if missing go; then pkg_install go golang go go; fi
-    # golangci-lint: packaged in nix, brew, and apk. On apt there is no
-    # package: download a specific release archive from GitHub and
-    # verify its hash (verify_sha256), never curl | sh.
-    if missing golangci-lint; then
-        pkg_install golangci-lint golangci-lint golangci-lint golangci-lint
-    fi
+    # No golangci-lint: script/lint runs it in Docker only.
     go mod download
 
     # ---- Python repos ----

script/fmt

@@ -19,7 +19,6 @@ main() {
     cd "$ROOT"
     ensure_pb
     gofumpt -l -w mfer internal cmd
-    golangci-lint run --fix
     # Markdown and JSON, over the same file set script/fmt-check verifies.
     "$SCRIPT_DIR/prettier" --write
 }

script/lint

@@ -1,17 +1,20 @@
 #!/bin/sh
-# script/lint: run the linter.
+# script/lint: run golangci-lint, in Docker only. Builds the lint stage of
+# the Dockerfile, whose build runs the linter, so a successful build is a
+# clean lint. --no-cache because a cached build runs no linter. The image
+# is removed afterwards, whatever the outcome.
 set -eu
 
-ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
+ROOT="$(cd "$SCRIPT_DIR/.." && pwd -P)"
 
 main() {
     cd "$ROOT"
-    golangci-lint run
-    if [ -n "$(gofmt -l .)" ]; then
-        echo "gofmt: files need formatting:" >&2
-        gofmt -l . >&2
-        exit 1
-    fi
+    # Tagged per run, so concurrent runs never remove each other's image.
+    image="$("$SCRIPT_DIR/projectname")-lint:$$"
+    # A failed build leaves no image, so there is nothing to remove then.
+    trap 'docker image rm "$image" >/dev/null 2>&1 || true' EXIT INT TERM
+    docker build --no-cache --target lint -t "$image" .
 }
 
 main "$@"