/go/store/blobstore/git_blobstore.go: wip, support all range

go/store/blobstore/git_blobstore.go

@@ -0,0 +1,117 @@
+// Copyright 2026 Dolthub, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package blobstore
+
+import (
+	"context"
+	"fmt"
+	"io"
+
+	git "github.com/dolthub/dolt/go/store/blobstore/internal/git"
+)
+
+// GitBlobstore is a Blobstore implementation backed by a git repository's object
+// database (bare repo or .git directory). It stores keys as paths within the tree
+// of the commit referenced by a git ref (e.g. refs/dolt/data).
+//
+// This initial implementation is intentionally READ-ONLY. Write-path methods
+// (Put / CheckAndPut / Concatenate) return an explicit unimplemented error while
+// we lock down read behavior for manifests and table files.
+type GitBlobstore struct {
+	gitDir string
+	ref    string
+	runner *git.Runner
+}
+
+var _ Blobstore = (*GitBlobstore)(nil)
+
+// NewGitBlobstore creates a new read-only GitBlobstore rooted at |gitDir| and |ref|.
+// |gitDir| should point at a bare repo directory or a .git directory.
+func NewGitBlobstore(gitDir, ref string) (*GitBlobstore, error) {
+	r, err := git.NewRunner(gitDir)
+	if err != nil {
+		return nil, err
+	}
+	return &GitBlobstore{gitDir: gitDir, ref: ref, runner: r}, nil
+}
+
+func (gbs *GitBlobstore) Path() string {
+	return fmt.Sprintf("%s@%s", gbs.gitDir, gbs.ref)
+}
+
+func (gbs *GitBlobstore) Exists(ctx context.Context, key string) (bool, error) {
+	commit, ok, err := git.TryResolveRefCommit(ctx, gbs.runner, gbs.ref)
+	if err != nil {
+		return false, err
+	}
+	if !ok {
+		return false, nil
+	}
+	_, err = git.ResolvePathBlob(ctx, gbs.runner, commit, key)
+	if err != nil {
+		if git.IsPathNotFound(err) {
+			return false, nil
+		}
+		return false, err
+	}
+	return true, nil
+}
+
+func (gbs *GitBlobstore) Get(ctx context.Context, key string, br BlobRange) (io.ReadCloser, uint64, string, error) {
+	commit, ok, err := git.TryResolveRefCommit(ctx, gbs.runner, gbs.ref)
+	if err != nil {
+		return nil, 0, "", err
+	}
+	if !ok {
+		return nil, 0, "", NotFound{Key: key}
+	}
+
+	blobOID, err := git.ResolvePathBlob(ctx, gbs.runner, commit, key)
+	if err != nil {
+		if git.IsPathNotFound(err) {
+			return nil, 0, commit.String(), NotFound{Key: key}
+		}
+		return nil, 0, commit.String(), err
+	}
+
+	sz, err := git.BlobSize(ctx, gbs.runner, blobOID)
+	if err != nil {
+		return nil, 0, commit.String(), err
+	}
+
+	// Range support is implemented in a follow-up task. For now, only AllRange.
+	if !br.isAllRange() {
+		return nil, uint64(sz), commit.String(), fmt.Errorf("%w: GitBlobstore.Get supports only AllRange (for now)", git.ErrUnimplemented)
+	}
+
+	rc, err := git.BlobReader(ctx, gbs.runner, blobOID)
+	if err != nil {
+		return nil, 0, commit.String(), err
+	}
+	return rc, uint64(sz), commit.String(), nil
+}
+
+func (gbs *GitBlobstore) Put(ctx context.Context, key string, totalSize int64, reader io.Reader) (string, error) {
+	return "", fmt.Errorf("%w: GitBlobstore.Put", git.ErrUnimplemented)
+}
+
+func (gbs *GitBlobstore) CheckAndPut(ctx context.Context, expectedVersion, key string, totalSize int64, reader io.Reader) (string, error) {
+	return "", fmt.Errorf("%w: GitBlobstore.CheckAndPut", git.ErrUnimplemented)
+}
+
+func (gbs *GitBlobstore) Concatenate(ctx context.Context, key string, sources []string) (string, error) {
+	return "", fmt.Errorf("%w: GitBlobstore.Concatenate", git.ErrUnimplemented)
+}
+