From 49fe20da31efed5409b61bc1a982ade70257d924 Mon Sep 17 00:00:00 2001
From: Justin Tobler <jtobler@gitlab.com>
Date: Tue, 23 Jan 2024 17:25:39 -0600
Subject: diff: Introduce `DiffBlob` RPC

---
 internal/gitaly/service/diff/diff_blob.go | 68 +++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)
 create mode 100644 internal/gitaly/service/diff/diff_blob.go

diff --git a/internal/gitaly/service/diff/diff_blob.go b/internal/gitaly/service/diff/diff_blob.go
new file mode 100644
index 000000000..6a13f1b70
--- /dev/null
+++ b/internal/gitaly/service/diff/diff_blob.go
@@ -0,0 +1,68 @@
+package diff
+
+import (
+	"fmt"
+
+	"gitlab.com/gitlab-org/gitaly/v16/internal/git"
+	"gitlab.com/gitlab-org/gitaly/v16/internal/gitaly/diff"
+	"gitlab.com/gitlab-org/gitaly/v16/internal/structerr"
+	"gitlab.com/gitlab-org/gitaly/v16/proto/go/gitalypb"
+)
+
+func (s *server) DiffBlob(in *gitalypb.DiffBlobRequest, stream gitalypb.DiffService_DiffBlobServer) error {
+	ctx := stream.Context()
+
+	repo := s.localrepo(in.GetRepository())
+
+	objectHash, err := repo.ObjectHash(ctx)
+	if err != nil {
+		return fmt.Errorf("detecting object format: %w", err)
+	}
+
+	gitCmd := git.Command{
+		Name: "diff",
+		Flags: []git.Option{
+			// The diff parser requires raw output even if only a single diff is generated.
+			git.Flag{Name: "--raw"},
+			git.Flag{Name: "--patch"},
+			git.Flag{Name: fmt.Sprintf("--abbrev=%d", objectHash.EncodedLen())},
+			git.Flag{Name: "--full-index"},
+			git.Flag{Name: "--no-prefix"},
+		},
+		Args: []string{in.LeftCommitId, in.RightCommitId},
+	}
+
+	cmd, err := repo.Exec(ctx, gitCmd, git.WithSetupStdout())
+	if err != nil {
+		return structerr.NewInternal("cmd: %w", err)
+	}
+
+	diffParser := diff.NewDiffParser(objectHash, cmd, diff.Limits{})
+
+	if !diffParser.Parse() {
+		return structerr.NewInternal("something went wrong")
+	}
+
+	blobDiff := diffParser.Diff()
+
+	if diffParser.Err() != nil {
+		return err
+	}
+
+	for len(blobDiff.Patch) > 0 {
+		resp := &gitalypb.DiffBlobResponse{
+			Patch: blobDiff.Patch,
+		}
+
+		if len(resp.Patch) > s.MsgSizeThreshold {
+			resp.Patch = blobDiff.Patch[:s.MsgSizeThreshold]
+			blobDiff.Patch = blobDiff.Patch[s.MsgSizeThreshold:]
+		}
+
+		if err := stream.Send(resp); err != nil {
+			return structerr.NewAborted("send: %w", err)
+		}
+	}
+
+	return nil
+}
-- 
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