feat: DTail fork — server/client feature development

Squashed development of the snonux/dtail fork's product code (internal/, cmd/)
since diverging from mimecast/dtail. Major areas:

- Read/output path: the former "turbo" channel-less path is now the single,
  default server-side read/output path for cat/grep/tail and MapReduce; the old
  channel-based path and its config/env toggles were removed.
- MapReduce: single aggregate implementation (server + serverless) fed directly
  by a processor pipeline, with input-exhausted finalization via the shutdown
  coordinator; high-concurrency and data-race fixes.
- Journal source reads (journal:unit.service) via journalctl, Linux-gated behind
  a journal-v1 capability.
- Auth-key fast reconnect: in-memory per-user public-key cache with TTL/max-keys,
  registered over an authenticated session (AUTHKEY), checked before
  authorized_keys.
- Interactive query reload (--interactive-query) with SESSION START/UPDATE
  generation boundaries and capability negotiation.
- Client-side deadlines: --timeout / --shutdownAfter as context deadlines;
  follow shutdown handling.
- Client logging: diagnostics-only daily log by default, opt-in payload tee via
  --log-payload.
- Numerous correctness fixes (buffer-pool double-recycle races, EOF-sentinel
  leaks, glob-expansion cap, TOCTOU in CSV parsing) with accompanying unit tests.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

1 files changed, 95 insertions, 0 deletions

diff --git a/internal/config/args_test.go b/internal/config/args_test.go
new file mode 100644
index 0000000..5e351a5
--- /dev/null
+++ b/internal/config/args_test.go
@@ -0,0 +1,95 @@
+package config
+
+import (
+	"encoding/base64"
+	"strings"
+	"testing"
+
+	"github.com/mimecast/dtail/internal/lcontext"
+)
+
+func TestSerializeOptionsUsesStableOrdering(t *testing.T) {
+	args := Args{
+		LContext:   lcontextForTest(3, 1, 2),
+		Plain:      true,
+		Quiet:      true,
+		Serverless: true,
+	}
+
+	got := args.SerializeOptions()
+	want := "after=2:before=1:max=3:plain=true:quiet=true:serverless=true"
+	if got != want {
+		t.Fatalf("unexpected serialized options:\nwant %q\ngot  %q", want, got)
+	}
+}
+
+func TestSerializeOptionsRoundTripsReservedValues(t *testing.T) {
+	unsafeValue := "a:b=c|d"
+	encodedValue := "base64%" + base64.StdEncoding.EncodeToString([]byte(unsafeValue))
+
+	got := serializeOptions(map[string]string{
+		"plain": "true",
+		"note":  unsafeValue,
+		"quiet": "false",
+	})
+
+	want := strings.Join([]string{
+		"note=" + encodedValue,
+		"plain=true",
+		"quiet=false",
+	}, ":")
+	if got != want {
+		t.Fatalf("unexpected serialized options:\nwant %q\ngot  %q", want, got)
+	}
+
+	options, ltx, err := DeserializeOptions(strings.Split(got, ":"))
+	if err != nil {
+		t.Fatalf("DeserializeOptions failed: %v", err)
+	}
+	if ltx != (lcontext.LContext{}) {
+		t.Fatalf("unexpected lcontext: %#v", ltx)
+	}
+	if options["note"] != unsafeValue {
+		t.Fatalf("expected note to round-trip, got %q", options["note"])
+	}
+	if options["plain"] != "true" {
+		t.Fatalf("expected plain to round-trip, got %q", options["plain"])
+	}
+	if options["quiet"] != "false" {
+		t.Fatalf("expected quiet to round-trip, got %q", options["quiet"])
+	}
+}
+
+func TestDeserializeOptionsAcceptsRawSerializedBlob(t *testing.T) {
+	unsafeValue := "a:b=c|d"
+	serialized := serializeOptions(map[string]string{
+		"note":  unsafeValue,
+		"plain": "true",
+		"quiet": "false",
+	})
+
+	options, ltx, err := DeserializeOptions([]string{serialized})
+	if err != nil {
+		t.Fatalf("DeserializeOptions failed: %v", err)
+	}
+	if ltx != (lcontext.LContext{}) {
+		t.Fatalf("unexpected lcontext: %#v", ltx)
+	}
+	if options["note"] != unsafeValue {
+		t.Fatalf("expected note to round-trip, got %q", options["note"])
+	}
+	if options["plain"] != "true" {
+		t.Fatalf("expected plain to round-trip, got %q", options["plain"])
+	}
+	if options["quiet"] != "false" {
+		t.Fatalf("expected quiet to round-trip, got %q", options["quiet"])
+	}
+}
+
+func lcontextForTest(max, before, after int) lcontext.LContext {
+	return lcontext.LContext{
+		MaxCount:      max,
+		BeforeContext: before,
+		AfterContext:  after,
+	}
+}