transport: Fix broken links to distribution docs (#2136)

The links are now pinned to an early 2019 API spec, which is when the code being
commented was written. Latest main was not used because the API has
changed slightly and the code would not match the referred API spec.

Signed-off-by: Guzman <[email protected]>

Author: guzalv

pkg/v1/remote/transport/error.go

@@ -25,7 +25,7 @@ import (
 )
 
 // Error implements error to support the following error specification:
-// https://github.com/docker/distribution/blob/master/docs/spec/api.md#errors
+// https://github.com/distribution/distribution/blob/aac2f6c8b7c5a6c60190848bab5cbeed2b5ba0a9/docs/spec/api.md#errors
 type Error struct {
 	Errors []Diagnostic `json:"errors,omitempty"`
 	// The http status code returned.
@@ -111,7 +111,7 @@ func (d Diagnostic) String() string {
 type ErrorCode string
 
 // The set of error conditions a registry may return:
-// https://github.com/docker/distribution/blob/master/docs/spec/api.md#errors-2
+// https://github.com/distribution/distribution/blob/aac2f6c8b7c5a6c60190848bab5cbeed2b5ba0a9/docs/spec/api.md#errors-2
 const (
 	BlobUnknownErrorCode         ErrorCode = "BLOB_UNKNOWN"
 	BlobUploadInvalidErrorCode   ErrorCode = "BLOB_UPLOAD_INVALID"
@@ -170,7 +170,7 @@ func CheckError(resp *http.Response, codes ...int) error {
 }
 
 func makeError(resp *http.Response, body []byte) *Error {
-	// https://github.com/docker/distribution/blob/master/docs/spec/api.md#errors
+	// https://github.com/distribution/distribution/blob/aac2f6c8b7c5a6c60190848bab5cbeed2b5ba0a9/docs/spec/api.md#errors
 	structuredError := &Error{}
 
 	// This can fail if e.g. the response body is not valid JSON. That's fine,