1 files changed, 69 insertions, 0 deletions
diff --git a/internal/gitutil/pull_request.go b/internal/gitutil/pull_request.go
new file mode 100644
index 00000000..818dc230
--- /dev/null
+++ b/internal/gitutil/pull_request.go
@@ -0,0 +1,69 @@
+// Copyright 2020 The Gogs Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package gitutil
+
+import (
+	"fmt"
+	"strconv"
+	"time"
+
+	"github.com/gogs/git-module"
+	"github.com/pkg/errors"
+	log "unknwon.dev/clog/v2"
+)
+
+// PullRequestMeta contains metadata for a pull request.
+type PullRequestMeta struct {
+	// The merge base of the pull request.
+	MergeBase string
+	// The commits that are requested to be merged.
+	Commits []*git.Commit
+	// The number of files changed.
+	NumFiles int
+}
+
+func (moduler) PullRequestMeta(headPath, basePath, headBranch, baseBranch string) (*PullRequestMeta, error) {
+	tmpRemoteBranch := baseBranch
+
+	// We need to create a temporary remote when the pull request is sent from a forked repository.
+	if headPath != basePath {
+		tmpRemote := strconv.FormatInt(time.Now().UnixNano(), 10)
+		err := Module.RepoAddRemote(headPath, tmpRemote, basePath, git.AddRemoteOptions{Fetch: true})
+		if err != nil {
+			return nil, fmt.Errorf("add remote: %v", err)
+		}
+		defer func() {
+			err := Module.RepoRemoveRemote(headPath, tmpRemote)
+			if err != nil {
+				log.Error("Failed to remove remote %q [path: %s]: %v", tmpRemote, headPath, err)
+				return
+			}
+		}()
+
+		tmpRemoteBranch = "remotes/" + tmpRemote + "/" + baseBranch
+	}
+
+	mergeBase, err := Module.RepoMergeBase(headPath, tmpRemoteBranch, headBranch)
+	if err != nil {
+		return nil, errors.Wrap(err, "get merge base")
+	}
+
+	commits, err := Module.RepoLog(headPath, mergeBase+"..."+headBranch)
+	if err != nil {
+		return nil, errors.Wrap(err, "get commits")
+	}
+
+	// Count number of changed files
+	names, err := Module.RepoDiffNameOnly(headPath, tmpRemoteBranch, headBranch, git.DiffNameOnlyOptions{NeedsMergeBase: true})
+	if err != nil {
+		return nil, errors.Wrap(err, "get changed files")
+	}
+
+	return &PullRequestMeta{
+		MergeBase: mergeBase,
+		Commits:   commits,
+		NumFiles:  len(names),
+	}, nil
+}