Run all linting in Docker via the Dockerfile lint stage (closes #90)

script/lint now builds only the lint stage of the main Dockerfile
(docker build --no-cache --target lint), whose build runs the linter, so
a successful build is a clean lint. It is uncached because a cached
build runs no linter, and a trap removes the image it tagged; the tag
carries the process ID so concurrent runs do not collide. The lint stage
calls golangci-lint directly, since make lint now needs Docker. Nothing
installs or runs golangci-lint on the host any more: bootstrap and the
Makefile drop the install, and script/fmt drops golangci-lint run --fix.

Model: opus-5-5

.golangci.yml

@@ -16,7 +16,6 @@ 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

@@ -69,10 +69,7 @@ RUN version="${VERSION:-$(git describe --tags --always)}"; \
         exit 1; \
     fi; \
     cd cmd/mfer && \
-    CGO_ENABLED=0 go build -tags urfave_cli_no_docs -ldflags "-X main.Gitrev=$version" -o /mfer .
+    go build -tags urfave_cli_no_docs -ldflags "-X main.Gitrev=$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

mfer/gpg_test.go

@@ -10,7 +10,6 @@ import (
 	"path/filepath"
 	"strconv"
 	"strings"
-	"syscall"
 	"testing"
 	"time"
 
@@ -426,51 +425,36 @@ func TestGPGTimeoutKillsGPG(t *testing.T) {
 	assert.Contains(t, err.Error(), "gpg sign failed: gpg timed out")
 }
 
-// TestGPGCancelWhenChildHoldsOutput uses a fake gpg that runs sleep as a
+// TestGPGTimeoutWhenChildHoldsOutput 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 once ctx ends instead of waiting
+// stderr open; the call must still return shortly after the deadline
-// for sleep to exit. The fake gpg writes the process ID of sleep to a named
+// instead of waiting for sleep to exit. The fake gpg writes the process ID
-// pipe; the test ends ctx only after reading it, so sleep is running by
+// of sleep to a file so that the test can kill it before returning.
-// then, and kills sleep before returning.
+func TestGPGTimeoutWhenChildHoldsOutput(t *testing.T) {
-func TestGPGCancelWhenChildHoldsOutput(t *testing.T) {
+	pidFile := filepath.Join(t.TempDir(), "sleep.pid")
-	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 60 &\necho $! >'"+pidPipe+"'\nwait\n"))
+		"#!/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)
 
-	ctx, cancel := context.WithCancel(context.Background())
+		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)
 	defer cancel()
 
-	signErr := make(chan error, 1)
+	start := time.Now()
-
+	_, err := gpgSign(ctx, []byte("data"), GPGKeyID("any"))
-	go func() {
+	require.ErrorIs(t, err, context.DeadlineExceeded)
-		_, err := gpgSign(ctx, []byte("data"), GPGKeyID("any"))
+	assert.Less(t, time.Since(start), 3*time.Second,
-		signErr <- err
+		"the call waited for the child holding gpg's output to exit")
-	}()
-
-	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

@@ -304,19 +304,46 @@ func TestScannerEnumerateFS(t *testing.T) {
 func TestSendEnumerateStatusNonBlocking(t *testing.T) {
 	t.Parallel()
 
-	// Nobody receives, so a blocking send would hang the test into its timeout.
+	// Channel with no buffer - send should not block
 	ch := make(chan EnumerateStatus)
 
-	sendEnumerateStatus(ch, EnumerateStatus{FilesFound: 1})
+	// 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")
+	}
 }
 
 func TestSendScanStatusNonBlocking(t *testing.T) {
 	t.Parallel()
 
-	// Nobody receives, so a blocking send would hang the test into its timeout.
+	// Channel with no buffer - send should not block
 	ch := make(chan ScanStatus)
 
-	sendScanStatus(ch, ScanStatus{ScannedFiles: 1})
+	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")
+	}
 }
 
 func TestSendStatusNilChannel(t *testing.T) {