internal/pkg: eliminate gzip-derived identifiers

These test cases are fragile to changes in package compress/gzip.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pkg/compress_test.go

@@ -36,6 +36,12 @@ func TestDecompress(t *testing.T) {
 		return (pkg.Checksum)(h.Sum(nil))
 	}()
 
+	gh := pkg.NewDecompress(pkg.NewHTTPGet(
+		&client,
+		"file:///testdata",
+		testdataChecksum,
+	), pkg.Gzip)
+
 	checkWithCache(t, []cacheTestCase{
 		{"decompress", 0, nil, func(t *testing.T, base *check.Absolute, c *pkg.Cache) {
 			cureMany(t, c, []cureStep{
@@ -48,11 +54,7 @@ func TestDecompress(t *testing.T) {
 					Want: pkg.Checksum{0xfd},
 				}},
 
-				{"gzip", pkg.NewDecompress(pkg.NewHTTPGet(
-					&client,
-					"file:///testdata",
-					testdataChecksum,
-				), pkg.Gzip), ignorePathname, expectsChecksum(sha512.Sum384([]byte{0})), pkg.WNew, nil},
+				{"gzip", gh, ignorePathname, expectsChecksum(sha512.Sum384([]byte{0})), pkg.WNew, nil},
 			})
 		}, expectsFS{
 			".": {Mode: fs.ModeDir | 0700},
@@ -61,7 +63,7 @@ func TestDecompress(t *testing.T) {
 			"checksum/" + pkg.Encode(sha512.Sum384([]byte{0})): {Mode: 0400, Data: []byte{0}},
 
 			"identifier": {Mode: fs.ModeDir | 0700},
-			"identifier/mae-iR_9LFT_BOEJ2IRzKsAlI754SalMjjt95fZeMd3gEyAzsrvuOXnXN0bFZJi4": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/vsAhtPNo4waRNOASwrQwcIPTqb3SBuJOXw2G4T1mNmVZM-wrQTRllmgXqcIIoRcX")},
+			"identifier/" + pkg.Encode(pkg.NewIR().Ident(gh).Value()): {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/vsAhtPNo4waRNOASwrQwcIPTqb3SBuJOXw2G4T1mNmVZM-wrQTRllmgXqcIIoRcX")},
 
 			"substitute": {Mode: fs.ModeDir | 0700},
 			"work":       {Mode: fs.ModeDir | 0700},