Add context propagation to rclone

- Change rclone/fs interfaces to accept context.Context
- Update interface implementations to use context.Context
- Change top level usage to propagate context to lover level functions

Context propagation is needed for stopping transfers and passing other
request-scoped values.

backend/http/http.go

@@ -5,6 +5,7 @@
 package http
 
 import (
+	"context"
 	"io"
 	"mime"
 	"net/http"
@@ -207,7 +208,7 @@ func (f *Fs) Precision() time.Duration {
 }
 
 // NewObject creates a new remote http file object
-func (f *Fs) NewObject(remote string) (fs.Object, error) {
+func (f *Fs) NewObject(ctx context.Context, remote string) (fs.Object, error) {
 	o := &Object{
 		fs:     f,
 		remote: remote,
@@ -359,7 +360,7 @@ func (f *Fs) readDir(dir string) (names []string, err error) {
 //
 // This should return ErrDirNotFound if the directory isn't
 // found.
-func (f *Fs) List(dir string) (entries fs.DirEntries, err error) {
+func (f *Fs) List(ctx context.Context, dir string) (entries fs.DirEntries, err error) {
 	if !strings.HasSuffix(dir, "/") && dir != "" {
 		dir += "/"
 	}
@@ -399,12 +400,12 @@ func (f *Fs) List(dir string) (entries fs.DirEntries, err error) {
 // May create the object even if it returns an error - if so
 // will return the object and the error, otherwise will return
 // nil and the error
-func (f *Fs) Put(in io.Reader, src fs.ObjectInfo, options ...fs.OpenOption) (fs.Object, error) {
+func (f *Fs) Put(ctx context.Context, in io.Reader, src fs.ObjectInfo, options ...fs.OpenOption) (fs.Object, error) {
 	return nil, errorReadOnly
 }
 
 // PutStream uploads to the remote path with the modTime given of indeterminate size
-func (f *Fs) PutStream(in io.Reader, src fs.ObjectInfo, options ...fs.OpenOption) (fs.Object, error) {
+func (f *Fs) PutStream(ctx context.Context, in io.Reader, src fs.ObjectInfo, options ...fs.OpenOption) (fs.Object, error) {
 	return nil, errorReadOnly
 }
 
@@ -427,7 +428,7 @@ func (o *Object) Remote() string {
 }
 
 // Hash returns "" since HTTP (in Go or OpenSSH) doesn't support remote calculation of hashes
-func (o *Object) Hash(r hash.Type) (string, error) {
+func (o *Object) Hash(ctx context.Context, r hash.Type) (string, error) {
 	return "", hash.ErrUnsupported
 }
 
@@ -437,7 +438,7 @@ func (o *Object) Size() int64 {
 }
 
 // ModTime returns the modification time of the remote http file
-func (o *Object) ModTime() time.Time {
+func (o *Object) ModTime(ctx context.Context) time.Time {
 	return o.modTime
 }
 
@@ -480,7 +481,7 @@ func (o *Object) stat() error {
 // SetModTime sets the modification and access time to the specified time
 //
 // it also updates the info field
-func (o *Object) SetModTime(modTime time.Time) error {
+func (o *Object) SetModTime(ctx context.Context, modTime time.Time) error {
 	return errorReadOnly
 }
 
@@ -490,7 +491,7 @@ func (o *Object) Storable() bool {
 }
 
 // Open a remote http file object for reading. Seek is supported
-func (o *Object) Open(options ...fs.OpenOption) (in io.ReadCloser, err error) {
+func (o *Object) Open(ctx context.Context, options ...fs.OpenOption) (in io.ReadCloser, err error) {
 	url := o.url()
 	req, err := http.NewRequest("GET", url, nil)
 	if err != nil {
@@ -517,27 +518,27 @@ func (f *Fs) Hashes() hash.Set {
 }
 
 // Mkdir makes the root directory of the Fs object
-func (f *Fs) Mkdir(dir string) error {
+func (f *Fs) Mkdir(ctx context.Context, dir string) error {
 	return errorReadOnly
 }
 
 // Remove a remote http file object
-func (o *Object) Remove() error {
+func (o *Object) Remove(ctx context.Context) error {
 	return errorReadOnly
 }
 
 // Rmdir removes the root directory of the Fs object
-func (f *Fs) Rmdir(dir string) error {
+func (f *Fs) Rmdir(ctx context.Context, dir string) error {
 	return errorReadOnly
 }
 
 // Update in to the object with the modTime given of the given size
-func (o *Object) Update(in io.Reader, src fs.ObjectInfo, options ...fs.OpenOption) error {
+func (o *Object) Update(ctx context.Context, in io.Reader, src fs.ObjectInfo, options ...fs.OpenOption) error {
 	return errorReadOnly
 }
 
 // MimeType of an Object if known, "" otherwise
-func (o *Object) MimeType() string {
+func (o *Object) MimeType(ctx context.Context) string {
 	return o.contentType
 }