func (s *CommitsService) GetMergeRequestsByCommit(pid interface{}, sha string, options ...OptionFunc) ([]*MergeRequest, *Response, error) {
	project, err := parseID(pid)
	if err != nil {
		return nil, nil, err
	}
	u := fmt.Sprintf("projects/%s/repository/commits/%s/merge_requests", pathEscape(project), sha)
	req, err := s.client.NewRequest("GET", u, nil, options)
	if err != nil {
		return nil, nil, err
	}
	var mrs []*MergeRequest
	resp, err := s.client.Do(req, &mrs)
	if err != nil {
		return nil, resp, err
	}
	return mrs, resp, err
}
GetMergeRequestsByCommit gets merge request associated with a commit.

GitLab API docs:
https://docs.gitlab.com/ce/api/commits.html#list-merge-requests-associated-with-a-commit
package gitlab
import (
	"fmt"
	"time"
)
type CommitsService struct {
	client *Client
}
type Commit struct {
	ID             string           `json:"id"`
	ShortID        string           `json:"short_id"`
	Title          string           `json:"title"`
	AuthorName     string           `json:"author_name"`
	AuthorEmail    string           `json:"author_email"`
	AuthoredDate   *time.Time       `json:"authored_date"`
	CommitterName  string           `json:"committer_name"`
	CommitterEmail string           `json:"committer_email"`
	CommittedDate  *time.Time       `json:"committed_date"`
	CreatedAt      *time.Time       `json:"created_at"`
	Message        string           `json:"message"`
	ParentIDs      []string         `json:"parent_ids"`
	Stats          *CommitStats     `json:"stats"`
	Status         *BuildStateValue `json:"status"`
	LastPipeline   *PipelineInfo    `json:"last_pipeline"`
	ProjectID      int              `json:"project_id"`
}
type CommitStats struct {
	Additions int `json:"additions"`
	Deletions int `json:"deletions"`
	Total     int `json:"total"`
}
func (c Commit) String() string {
	return Stringify(c)
}
type ListCommitsOptions struct {
	ListOptions
	RefName   *string    `url:"ref_name,omitempty" json:"ref_name,omitempty"`
	Since     *time.Time `url:"since,omitempty" json:"since,omitempty"`
	Until     *time.Time `url:"until,omitempty" json:"until,omitempty"`
	Path      *string    `url:"path,omitempty" json:"path,omitempty"`
	All       *bool      `url:"all,omitempty" json:"all,omitempty"`
	WithStats *bool      `url:"with_stats,omitempty" json:"with_stats,omitempty"`
}
func (s *CommitsService) ListCommits(pid interface{}, opt *ListCommitsOptions, options ...OptionFunc) ([]*Commit, *Response, error) {
	project, err := parseID(pid)
	if err != nil {
		return nil, nil, err
	}
	u := fmt.Sprintf("projects/%s/repository/commits", pathEscape(project))
	req, err := s.client.NewRequest("GET", u, opt, options)
	if err != nil {
		return nil, nil, err
	}
	var c []*Commit
	resp, err := s.client.Do(req, &c)
	if err != nil {
		return nil, resp, err
	}
	return c, resp, err
}
type FileAction string
const (
	FileCreate FileAction = "create"
	FileDelete FileAction = "delete"
	FileMove   FileAction = "move"
	FileUpdate FileAction = "update"
)
type CommitAction struct {
	Action       FileAction `url:"action" json:"action"`
	FilePath     string     `url:"file_path" json:"file_path"`
	PreviousPath string     `url:"previous_path,omitempty" json:"previous_path,omitempty"`
	Content      string     `url:"content,omitempty" json:"content,omitempty"`
	Encoding     string     `url:"encoding,omitempty" json:"encoding,omitempty"`
}
type CommitRef struct {
	Type string `json:"type"`
	Name string `json:"name"`
}
type GetCommitRefsOptions struct {
	ListOptions
	Type *string `url:"type,omitempty" json:"type,omitempty"`
}
func (s *CommitsService) GetCommitRefs(pid interface{}, sha string, opt *GetCommitRefsOptions, options ...OptionFunc) ([]CommitRef, *Response, error) {
	project, err := parseID(pid)
	if err != nil {
		return nil, nil, err
	}
	u := fmt.Sprintf("projects/%s/repository/commits/%s/refs", pathEscape(project), sha)
	req, err := s.client.NewRequest("GET", u, opt, options)
	if err != nil {
		return nil, nil, err
	}
	var cs []CommitRef
	resp, err := s.client.Do(req, &cs)
	if err != nil {
		return nil, resp, err
	}
	return cs, resp, err
}
func (s *CommitsService) GetCommit(pid interface{}, sha string, options ...OptionFunc) (*Commit, *Response, error) {
	project, err := parseID(pid)
	if err != nil {
		return nil, nil, err
	}
	u := fmt.Sprintf("projects/%s/repository/commits/%s", pathEscape(project), sha)
	req, err := s.client.NewRequest("GET", u, nil, options)
	if err != nil {
		return nil, nil, err
	}
	c := new(Commit)
	resp, err := s.client.Do(req, c)
	if err != nil {
		return nil, resp, err
	}
	return c, resp, err
}
type CreateCommitOptions struct {
	Branch        *string         `url:"branch" json:"branch"`
	CommitMessage *string         `url:"commit_message" json:"commit_message"`
	StartBranch   *string         `url:"start_branch,omitempty" json:"start_branch,omitempty"`
	Actions       []*CommitAction `url:"actions" json:"actions"`
	AuthorEmail   *string         `url:"author_email,omitempty" json:"author_email,omitempty"`
	AuthorName    *string         `url:"author_name,omitempty" json:"author_name,omitempty"`
}
func (s *CommitsService) CreateCommit(pid interface{}, opt *CreateCommitOptions, options ...OptionFunc) (*Commit, *Response, error) {
	project, err := parseID(pid)
	if err != nil {
		return nil, nil, err
	}
	u := fmt.Sprintf("projects/%s/repository/commits", pathEscape(project))
	req, err := s.client.NewRequest("POST", u, opt, options)
	if err != nil {
		return nil, nil, err
	}
	var c *Commit
	resp, err := s.client.Do(req, &c)
	if err != nil {
		return nil, resp, err
	}
	return c, resp, err
}
type Diff struct {
	Diff        string `json:"diff"`
	NewPath     string `json:"new_path"`
	OldPath     string `json:"old_path"`
	AMode       string `json:"a_mode"`
	BMode       string `json:"b_mode"`
	NewFile     bool   `json:"new_file"`
	RenamedFile bool   `json:"renamed_file"`
	DeletedFile bool   `json:"deleted_file"`
}
func (d Diff) String() string {
	return Stringify(d)
}
type GetCommitDiffOptions ListOptions
func (s *CommitsService) GetCommitDiff(pid interface{}, sha string, opt *GetCommitDiffOptions, options ...OptionFunc) ([]*Diff, *Response, error) {
	project, err := parseID(pid)
	if err != nil {
		return nil, nil, err
	}
	u := fmt.Sprintf("projects/%s/repository/commits/%s/diff", pathEscape(project), sha)
	req, err := s.client.NewRequest("GET", u, opt, options)
	if err != nil {
		return nil, nil, err
	}
	var d []*Diff
	resp, err := s.client.Do(req, &d)
	if err != nil {
		return nil, resp, err
	}
	return d, resp, err
}
type CommitComment struct {
	Note     string `json:"note"`
	Path     string `json:"path"`
	Line     int    `json:"line"`
	LineType string `json:"line_type"`
	Author   Author `json:"author"`
}
type Author struct {
	ID        int        `json:"id"`
	Username  string     `json:"username"`
	Email     string     `json:"email"`
	Name      string     `json:"name"`
	State     string     `json:"state"`
	Blocked   bool       `json:"blocked"`
	CreatedAt *time.Time `json:"created_at"`
}
func (c CommitComment) String() string {
	return Stringify(c)
}
type GetCommitCommentsOptions ListOptions
func (s *CommitsService) GetCommitComments(pid interface{}, sha string, opt *GetCommitCommentsOptions, options ...OptionFunc) ([]*CommitComment, *Response, error) {
	project, err := parseID(pid)
	if err != nil {
		return nil, nil, err
	}
	u := fmt.Sprintf("projects/%s/repository/commits/%s/comments", pathEscape(project), sha)
	req, err := s.client.NewRequest("GET", u, opt, options)
	if err != nil {
		return nil, nil, err
	}
	var c []*CommitComment
	resp, err := s.client.Do(req, &c)
	if err != nil {
		return nil, resp, err
	}
	return c, resp, err
}
type PostCommitCommentOptions struct {
	Note     *string `url:"note,omitempty" json:"note,omitempty"`
	Path     *string `url:"path" json:"path"`
	Line     *int    `url:"line" json:"line"`
	LineType *string `url:"line_type" json:"line_type"`
}
func (s *CommitsService) PostCommitComment(pid interface{}, sha string, opt *PostCommitCommentOptions, options ...OptionFunc) (*CommitComment, *Response, error) {
	project, err := parseID(pid)
	if err != nil {
		return nil, nil, err
	}
	u := fmt.Sprintf("projects/%s/repository/commits/%s/comments", pathEscape(project), sha)
	req, err := s.client.NewRequest("POST", u, opt, options)
	if err != nil {
		return nil, nil, err
	}
	c := new(CommitComment)
	resp, err := s.client.Do(req, c)
	if err != nil {
		return nil, resp, err
	}
	return c, resp, err
}
type GetCommitStatusesOptions struct {
	ListOptions
	Ref   *string `url:"ref,omitempty" json:"ref,omitempty"`
	Stage *string `url:"stage,omitempty" json:"stage,omitempty"`
	Name  *string `url:"name,omitempty" json:"name,omitempty"`
	All   *bool   `url:"all,omitempty" json:"all,omitempty"`
}
type CommitStatus struct {
	ID          int        `json:"id"`
	SHA         string     `json:"sha"`
	Ref         string     `json:"ref"`
	Status      string     `json:"status"`
	Name        string     `json:"name"`
	TargetURL   string     `json:"target_url"`
	Description string     `json:"description"`
	CreatedAt   *time.Time `json:"created_at"`
	StartedAt   *time.Time `json:"started_at"`
	FinishedAt  *time.Time `json:"finished_at"`
	Author      Author     `json:"author"`
}
func (s *CommitsService) GetCommitStatuses(pid interface{}, sha string, opt *GetCommitStatusesOptions, options ...OptionFunc) ([]*CommitStatus, *Response, error) {
	project, err := parseID(pid)
	if err != nil {
		return nil, nil, err
	}
	u := fmt.Sprintf("projects/%s/repository/commits/%s/statuses", pathEscape(project), sha)
	req, err := s.client.NewRequest("GET", u, opt, options)
	if err != nil {
		return nil, nil, err
	}
	var cs []*CommitStatus
	resp, err := s.client.Do(req, &cs)
	if err != nil {
		return nil, resp, err
	}
	return cs, resp, err
}
type SetCommitStatusOptions struct {
	State       BuildStateValue `url:"state" json:"state"`
	Ref         *string         `url:"ref,omitempty" json:"ref,omitempty"`
	Name        *string         `url:"name,omitempty" json:"name,omitempty"`
	Context     *string         `url:"context,omitempty" json:"context,omitempty"`
	TargetURL   *string         `url:"target_url,omitempty" json:"target_url,omitempty"`
	Description *string         `url:"description,omitempty" json:"description,omitempty"`
}
func (s *CommitsService) SetCommitStatus(pid interface{}, sha string, opt *SetCommitStatusOptions, options ...OptionFunc) (*CommitStatus, *Response, error) {
	project, err := parseID(pid)
	if err != nil {
		return nil, nil, err
	}
	u := fmt.Sprintf("projects/%s/statuses/%s", pathEscape(project), sha)
	req, err := s.client.NewRequest("POST", u, opt, options)
	if err != nil {
		return nil, nil, err
	}
	var cs *CommitStatus
	resp, err := s.client.Do(req, &cs)
	if err != nil {
		return nil, resp, err
	}
	return cs, resp, err
}