Move migrations into services and base into modules/migration (#17663)

* Move migrtions into services and base into modules/migration

* Fix imports

* Fix lint

modules/migration/pullrequest.go

@@ -0,0 +1,61 @@
+// Copyright 2019 The Gitea Authors. All rights reserved.
+// Copyright 2018 Jonas Franz. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package migration
+
+import (
+	"fmt"
+	"time"
+)
+
+// PullRequest defines a standard pull request information
+type PullRequest struct {
+	Number         int64
+	Title          string
+	PosterName     string `yaml:"poster_name"`
+	PosterID       int64  `yaml:"poster_id"`
+	PosterEmail    string `yaml:"poster_email"`
+	Content        string
+	Milestone      string
+	State          string
+	Created        time.Time
+	Updated        time.Time
+	Closed         *time.Time
+	Labels         []*Label
+	PatchURL       string `yaml:"patch_url"`
+	Merged         bool
+	MergedTime     *time.Time `yaml:"merged_time"`
+	MergeCommitSHA string     `yaml:"merge_commit_sha"`
+	Head           PullRequestBranch
+	Base           PullRequestBranch
+	Assignees      []string
+	IsLocked       bool `yaml:"is_locked"`
+	Reactions      []*Reaction
+	Context        IssueContext `yaml:"-"`
+}
+
+// IsForkPullRequest returns true if the pull request from a forked repository but not the same repository
+func (p *PullRequest) IsForkPullRequest() bool {
+	return p.Head.RepoPath() != p.Base.RepoPath()
+}
+
+// GetGitRefName returns pull request relative path to head
+func (p PullRequest) GetGitRefName() string {
+	return fmt.Sprintf("refs/pull/%d/head", p.Number)
+}
+
+// PullRequestBranch represents a pull request branch
+type PullRequestBranch struct {
+	CloneURL  string `yaml:"clone_url"`
+	Ref       string
+	SHA       string
+	RepoName  string `yaml:"repo_name"`
+	OwnerName string `yaml:"owner_name"`
+}
+
+// RepoPath returns pull request repo path
+func (p PullRequestBranch) RepoPath() string {
+	return fmt.Sprintf("%s/%s", p.OwnerName, p.RepoName)
+}