feat: Add Stack field to PullRequest for stacked pull requests

github/pulls.go

@@ -87,6 +87,7 @@ type PullRequest struct {
 	Links *PRLinks           `json:"_links,omitempty"`
 	Head  *PullRequestBranch `json:"head,omitempty"`
 	Base  *PullRequestBranch `json:"base,omitempty"`
+	Stack *PullRequestStack  `json:"stack,omitempty"`
 
 	// ActiveLockReason is populated only when LockReason is provided while locking the pull request.
 	// Possible values are: "off-topic", "too heated", "resolved", and "spam".
@@ -123,6 +124,31 @@ type PullRequestBranch struct {
 	User  *User       `json:"user,omitempty"`
 }
 
+// PullRequestStack represents the stack a pull request belongs to, in
+// repositories that use stacked pull requests. Base reports the branch the
+// entire stack ultimately targets, which can differ from the pull request's own
+// Base branch (the branch below it in the stack).
+type PullRequestStack struct {
+	// Base is the base of the stack: the branch the entire stack ultimately targets.
+	Base *PullRequestStackBase `json:"base"`
+	// Size is the total number of pull requests in the stack.
+	Size *int `json:"size,omitempty"`
+	// Position is the one-based position of this pull request within the stack,
+	// where 1 is the bottom of the stack.
+	Position *int `json:"position,omitempty"`
+	// ID is the ID of the stack that this pull request belongs to.
+	ID *int64 `json:"id,omitempty"`
+	// Number is the number of the stack that this pull request belongs to.
+	Number *int `json:"number,omitempty"`
+}
+
+// PullRequestStackBase represents the base of a stacked pull request's stack:
+// the branch the entire stack ultimately targets.
+type PullRequestStackBase struct {
+	Ref string `json:"ref"`
+	SHA string `json:"sha"`
+}
+
 // PullRequestListOptions specifies the optional parameters to the
 // PullRequestsService.List method.
 type PullRequestListOptions struct {