git: clone --shared implemented

1 files changed, 26 insertions, 0 deletions

diff --git a/repository.go b/repository.go
index 013b53f..4898838 100644
--- a/repository.go
+++ b/repository.go
@@ -22,6 +22,7 @@ import (
 	"github.com/go-git/go-git/v5/config"
 	"github.com/go-git/go-git/v5/internal/path_util"
 	"github.com/go-git/go-git/v5/internal/revision"
+	"github.com/go-git/go-git/v5/internal/url"
 	"github.com/go-git/go-git/v5/plumbing"
 	"github.com/go-git/go-git/v5/plumbing/cache"
 	formatcfg "github.com/go-git/go-git/v5/plumbing/format/config"
@@ -62,6 +63,7 @@ var (
 	ErrUnableToResolveCommit     = errors.New("unable to resolve commit")
 	ErrPackedObjectsNotSupported = errors.New("packed objects not supported")
 	ErrSHA256NotSupported        = errors.New("go-git was not compiled with SHA256 support")
+	ErrAlternatePathNotSupported = errors.New("alternate path must use the file scheme")
 )
 
 // Repository represents a git repository
@@ -887,6 +889,30 @@ func (r *Repository) clone(ctx context.Context, o *CloneOptions) error {
 		return err
 	}
 
+	// When the repository to clone is on the local machine,
+	// instead of using hard links, automatically setup .git/objects/info/alternates
+	// to share the objects with the source repository
+	if o.Shared {
+		if !url.IsLocalEndpoint(o.URL) {
+			return ErrAlternatePathNotSupported
+		}
+		altpath := o.URL
+		remoteRepo, err := PlainOpen(o.URL)
+		if err != nil {
+			return fmt.Errorf("failed to open remote repository: %w", err)
+		}
+		conf, err := remoteRepo.Config()
+		if err != nil {
+			return fmt.Errorf("failed to read remote repository configuration: %w", err)
+		}
+		if !conf.Core.IsBare {
+			altpath = path.Join(altpath, GitDirName)
+		}
+		if err := r.Storer.AddAlternate(altpath); err != nil {
+			return fmt.Errorf("failed to add alternate file to git objects dir: %w", err)
+		}
+	}
+
 	ref, err := r.fetchAndUpdateReferences(ctx, &FetchOptions{
 		RefSpecs:        c.Fetch,
 		Depth:           o.Depth,