feat(redmine): partial UpdateVersion and GetVersion with fake endpoints

UpdateVersion issues PUT /versions/N.json sending only the fields the
caller set (untouched attributes never travel), and never parses the
empty 204 body Redmine answers with. GetVersion backs re-fetching one
milestone. The fake serves both endpoints with Redmine's semantics
(partial apply, 204 empty, 404 for unknown ids), and table tests pin
the exact request bodies, partiality, and error mapping.

💘 Generated with Crush

Assisted-by: Crush:glm-5.2

redmine/projects.go

@@ -16,11 +16,12 @@ type Version struct {
 	Sharing string `json:"sharing,omitempty"`
 }
 
-// VersionParams is the write shape for CreateVersion.
+// VersionParams is the write shape for CreateVersion/UpdateVersion. On
+// update, zero fields are omitted so only what you set travels.
 type VersionParams struct {
 	Name    string
 	DueDate string
-	Status  string // "" defaults to open on the server
+	Status  string // "" defaults to open on create; omitted on update
 	Sharing string // "" omits; "descendants" mirrors the PMO roadmap scripts
 }
 
@@ -55,6 +56,41 @@ func (c *Client) CreateVersion(ctx context.Context, project string, p VersionPar
 	return &body.Version, nil
 }
 
+// UpdateVersion partially updates a version (PUT /versions/N.json).
+// The server answers 204 with an EMPTY body — it is never parsed. Only
+// the fields set in p are sent; untouched attributes are not clobbered.
+func (c *Client) UpdateVersion(ctx context.Context, id int, p VersionParams) error {
+	fields := map[string]any{}
+	if p.Name != "" {
+		fields["name"] = p.Name
+	}
+	if p.DueDate != "" {
+		fields["due_date"] = p.DueDate
+	}
+	if p.Status != "" {
+		fields["status"] = p.Status
+	}
+	if p.Sharing != "" {
+		fields["sharing"] = p.Sharing
+	}
+	if len(fields) == 0 {
+		return fmt.Errorf("%w: nothing to update", ErrValidation)
+	}
+	payload := map[string]any{"version": fields}
+	return c.do(ctx, "PUT", "/versions/"+strconv.Itoa(id)+".json", nil, payload, nil)
+}
+
+// GetVersion fetches one version by id.
+func (c *Client) GetVersion(ctx context.Context, id int) (*Version, error) {
+	var body struct {
+		Version Version `json:"version"`
+	}
+	if err := c.do(ctx, "GET", "/versions/"+strconv.Itoa(id)+".json", nil, nil, &body); err != nil {
+		return nil, err
+	}
+	return &body.Version, nil
+}
+
 // Category is an issue category within a project.
 type Category struct {
 	ID   int    `json:"id"`