feat(go-config): multi-format codecs, envc CLI, fixtures, ASRs

- Module github.com/eslider/go-config with env/yaml/json/ini packages
- internal: source, keymap, merge, structconv, bytesutil
- cmd/envc: convert, get, merge
- docs/asr ASR-0001..0008, README/CHANGELOG/AGENTS refresh
- golangci-lint v2 config; tests + fixtures

Co-authored-by: Cursor <cursoragent@cursor.com>

cmd/envc/convert.go

@@ -0,0 +1,96 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"flag"
+	"fmt"
+	"io"
+
+	"github.com/eslider/go-config/env"
+	"github.com/eslider/go-config/ini"
+	"github.com/eslider/go-config/internal/bytesutil"
+	libjson "github.com/eslider/go-config/json"
+	"github.com/eslider/go-config/yaml"
+	yaml3 "gopkg.in/yaml.v3"
+)
+
+// RunConvert implements: envc convert --from F --to T [--input] [--output].
+func RunConvert(args []string, stdin io.Reader, stdout, stderr io.Writer) int {
+	fs := flag.NewFlagSet("convert", flag.ContinueOnError)
+	fs.SetOutput(stderr)
+	from := fs.String("from", "", "source format: yaml|json|ini|env")
+	to := fs.String("to", "", "target format: yaml|json|ini|env")
+	input := fs.String("input", "-", "input path, URL, or - for stdin")
+	output := fs.String("output", "-", "output path or - for stdout")
+	if err := fs.Parse(args); err != nil {
+		return 2
+	}
+	if *from == "" || *to == "" {
+		_, _ = fmt.Fprintln(stderr, "convert: --from and --to are required")
+		return 2
+	}
+	ctx := context.Background()
+	src := openSource(*input, stdin)
+	b, err := bytesutil.ReadAll(ctx, src)
+	if err != nil {
+		_, _ = fmt.Fprintf(stderr, "convert: read: %v\n", err)
+		return 1
+	}
+	m, err := loadMapFromBytes(ctx, *from, b)
+	if err != nil {
+		_, _ = fmt.Fprintf(stderr, "convert: parse: %v\n", err)
+		return 1
+	}
+	outb, err := marshalMap(*to, m)
+	if err != nil {
+		_, _ = fmt.Fprintf(stderr, "convert: marshal: %v\n", err)
+		return 1
+	}
+	out, err := openOutput(*output, stdout)
+	if err != nil {
+		_, _ = fmt.Fprintf(stderr, "convert: output: %v\n", err)
+		return 1
+	}
+	defer func() { _ = out.Close() }()
+	if _, err := out.Write(outb); err != nil {
+		_, _ = fmt.Fprintf(stderr, "convert: write: %v\n", err)
+		return 1
+	}
+	if *output == "-" || *output == "" {
+		if len(outb) > 0 && outb[len(outb)-1] != '\n' {
+			_, _ = out.Write([]byte("\n"))
+		}
+	}
+	return 0
+}
+
+func loadMapFromBytes(ctx context.Context, format string, b []byte) (map[string]any, error) {
+	switch format {
+	case "yaml":
+		return yaml.New(yaml.WithBytes(b)).Map(ctx)
+	case "json":
+		return libjson.New(libjson.WithBytes(b)).Map(ctx)
+	case "ini":
+		return ini.New(ini.WithBytes(b)).Map(ctx)
+	case "env":
+		return env.New(env.WithBytes(b)).Map(ctx)
+	default:
+		return nil, fmt.Errorf("unknown format %q", format)
+	}
+}
+
+func marshalMap(format string, m map[string]any) ([]byte, error) {
+	switch format {
+	case "yaml":
+		return yaml3.Marshal(m)
+	case "json":
+		return json.MarshalIndent(m, "", "  ")
+	case "ini":
+		return ini.New().Marshal(m)
+	case "env":
+		return env.New().Marshal(m)
+	default:
+		return nil, fmt.Errorf("unknown format %q", format)
+	}
+}