test: add a bunch of new tests and fixes

- do not expect specific filename, that's impl. detail
- add new fixtures, rename some, delete others
- fix byte range tests (limit is inclusive)
- dag-cbor tests with links
- content-type and content-disposition checks in all car tests
- and much more

Author: hacdias

fixtures/t0118-carv1-basic.car

@@ -6,8 +6,8 @@ package car
 import (
 	"bytes"
 	"context"
+	"errors"
 	"fmt"
-	dagpb "github.com/ipld/go-codec-dagpb"
 	"io"
 	"os"
 	"path"
@@ -22,6 +22,7 @@ import (
 	"github.com/ipfs/go-cid"
 	format "github.com/ipfs/go-ipld-format"
 	"github.com/ipfs/go-unixfsnode"
+	dagpb "github.com/ipld/go-codec-dagpb"
 	"github.com/ipld/go-ipld-prime"
 	_ "github.com/ipld/go-ipld-prime/codec/cbor"
 	_ "github.com/ipld/go-ipld-prime/codec/dagcbor"
@@ -78,15 +79,27 @@ func (d *UnixfsDag) loadLinks(node format.Node) (map[string]*UnixfsDag, error) {
 }
 
 func (d *UnixfsDag) getNode(names ...string) (format.Node, error) {
-	for _, name := range names {
+	for i, name := range names {
 		node, err := d.getNode()
 		if err != nil {
 			return nil, err
 		}
 
 		if d.links == nil {
 			d.links, err = d.loadLinks(node)
-			if err != nil {
+			if errors.Is(err, uio.ErrNotADir) {
+				// Maybe it's an IPLD Link!
+				lnk, _, err := node.ResolveLink(names[i:])
+				if err != nil {
+					return nil, fmt.Errorf("node is neither a unixfs directory, or includes an ipld link: %w", err)
+				}
+				n, err := lnk.GetNode(context.Background(), d.dsvc)
+				if err != nil {
+					return nil, fmt.Errorf("found link node could not be fetched: %w", err)
+				}
+				d.node = n
+				return d.node, nil
+			} else if err != nil {
 				return nil, err
 			}
 		}
@@ -173,16 +186,6 @@ func (d *UnixfsDag) MustGetChildrenCids(names ...string) []string {
 	return cids
 }
 
-func (d *UnixfsDag) MustGetIPLDChildrenCids(names ...string) []string {
-	node := d.MustGetNode(names...)
-	lnks := node.node.Links()
-	var cids []string
-	for _, l := range lnks {
-		cids = append(cids, l.Cid.String())
-	}
-	return cids
-}
-
 // MustGetCidsInHAMT returns the cids in the HAMT at the given path. Does not include the CID of the HAMT root
 func (d *UnixfsDag) MustGetCidsInHAMT(names ...string) []string {
 	node := d.MustGetNode(names...)