Move some functions to gitrepo package to reduce RepoPath reference directly (#36126)

modules/gitrepo/diff.go

@@ -4,8 +4,10 @@
 package gitrepo
 
 import (
+	"bytes"
 	"context"
 	"fmt"
+	"io"
 	"regexp"
 	"strconv"
 
@@ -60,3 +62,15 @@ func parseDiffStat(stdout string) (numFiles, totalAdditions, totalDeletions int,
 	}
 	return numFiles, totalAdditions, totalDeletions, err
 }
+
+// GetReverseRawDiff dumps the reverse diff results of repository in given commit ID to io.Writer.
+func GetReverseRawDiff(ctx context.Context, repo Repository, commitID string, writer io.Writer) error {
+	stderr := new(bytes.Buffer)
+	if err := RunCmd(ctx, repo, gitcmd.NewCommand("show", "--pretty=format:revert %H%n", "-R").
+		AddDynamicArguments(commitID).
+		WithStdout(writer).
+		WithStderr(stderr)); err != nil {
+		return fmt.Errorf("GetReverseRawDiff: %w - %s", err, stderr)
+	}
+	return nil
+}