internal/testgit: Add helpers to prepare for commit testing

3 files changed, 88 insertions, 0 deletions

diff --git a/internal/testgit/commit.go b/internal/testgit/commit.go
new file mode 100644
index 00000000..09a5438d
--- /dev/null
+++ b/internal/testgit/commit.go
@@ -0,0 +1,34 @@
+package testgit
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+
+	"lindenii.org/go/furgit/object/id"
+)
+
+// CommitTree creates a commit object from a tree and optional parents,
+// and returns its object ID.
+func (repo *Repo) CommitTree(tb testing.TB, tree id.ObjectID, message string, parents ...id.ObjectID) (id.ObjectID, error) {
+	tb.Helper()
+
+	args := []string{"commit-tree", tree.String()}
+	for _, parent := range parents {
+		args = append(args, "-p", parent.String())
+	}
+
+	args = append(args, "-m", message)
+
+	stdout, err := repo.Run(tb, nil, "git", args...)
+	if err != nil {
+		return id.ObjectID{}, fmt.Errorf("commit-tree: %w", err)
+	}
+
+	commitID, err := repo.objectFormat.FromString(strings.TrimSuffix(string(stdout), "\n"))
+	if err != nil {
+		return id.ObjectID{}, fmt.Errorf("parse git commit-tree output %q: %w", string(stdout), err)
+	}
+
+	return commitID, nil
+}
diff --git a/internal/testgit/object.go b/internal/testgit/object.go
index a5f7163b..cbdfce76 100644
--- a/internal/testgit/object.go
+++ b/internal/testgit/object.go
@@ -27,3 +27,16 @@ func (repo *Repo) HashObject(tb testing.TB, ty typ.Type, body io.Reader) (id.Obj
 
 	return objectID, nil
 }
+
+// CatFile returns the raw content of an object
+// (without the "type size\x00" header).
+func (repo *Repo) CatFile(tb testing.TB, ty typ.Type, oid id.ObjectID) ([]byte, error) {
+	tb.Helper()
+
+	stdout, err := repo.Run(tb, nil, "git", "cat-file", ty.Name(), oid.String())
+	if err != nil {
+		return nil, fmt.Errorf("cat-file: %w", err)
+	}
+
+	return stdout, nil
+}
diff --git a/internal/testgit/tree.go b/internal/testgit/tree.go
new file mode 100644
index 00000000..3f80d1c3
--- /dev/null
+++ b/internal/testgit/tree.go
@@ -0,0 +1,41 @@
+package testgit
+
+import (
+	"bytes"
+	"fmt"
+	"strings"
+	"testing"
+
+	"lindenii.org/go/furgit/object/id"
+	"lindenii.org/go/furgit/object/typ"
+)
+
+// MkTreeEntry is one entry of a tree built by [Repo.MkTree].
+type MkTreeEntry struct {
+	Mode string
+	Type typ.Type
+	OID  id.ObjectID
+	Name string
+}
+
+// MkTree builds a tree object from entries and returns its object ID.
+func (repo *Repo) MkTree(tb testing.TB, entries []MkTreeEntry) (id.ObjectID, error) {
+	tb.Helper()
+
+	var stdin bytes.Buffer
+	for _, entry := range entries {
+		fmt.Fprintf(&stdin, "%s %s %s\t%s\n", entry.Mode, entry.Type.Name(), entry.OID.String(), entry.Name)
+	}
+
+	stdout, err := repo.Run(tb, &stdin, "git", "mktree")
+	if err != nil {
+		return id.ObjectID{}, fmt.Errorf("mktree: %w", err)
+	}
+
+	treeID, err := repo.objectFormat.FromString(strings.TrimSuffix(string(stdout), "\n"))
+	if err != nil {
+		return id.ObjectID{}, fmt.Errorf("parse git mktree output %q: %w", string(stdout), err)
+	}
+
+	return treeID, nil
+}