1 files changed, 45 insertions, 4 deletions
diff --git a/internal/testgit/commit.go b/internal/testgit/commit.go
index 09a5438d..b33b8904 100644
--- a/internal/testgit/commit.go
+++ b/internal/testgit/commit.go
@@ -8,19 +8,60 @@ import (
 	"lindenii.org/go/furgit/object/id"
 )
 
+// CommitTreeIdentity configures an author or committer identity
+// for [Repo.CommitTree].
+type CommitTreeIdentity struct {
+	Name  string
+	Email string
+}
+
+// CommitTreeOptions configures [Repo.CommitTree].
+type CommitTreeOptions struct {
+	Message       string
+	Author        CommitTreeIdentity
+	Committer     CommitTreeIdentity
+	AuthorDate    string
+	CommitterDate string
+}
+
 // 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) {
+func (repo *Repo) CommitTree(
+	tb testing.TB,
+	tree id.ObjectID,
+	opts CommitTreeOptions,
+	parents ...id.ObjectID,
+) (id.ObjectID, error) {
 	tb.Helper()
 
-	args := []string{"commit-tree", tree.String()}
+	args := []string{"commit-tree"}
 	for _, parent := range parents {
 		args = append(args, "-p", parent.String())
 	}
 
-	args = append(args, "-m", message)
+	args = append(args, "-m", opts.Message, "--end-of-options", tree.String())
+
+	cmd := repo.Command(tb, "git", args...)
+	if opts.Author.Name != "" {
+		cmd.Env = setEnv(cmd.Env, "GIT_AUTHOR_NAME", opts.Author.Name)
+	}
+	if opts.Author.Email != "" {
+		cmd.Env = setEnv(cmd.Env, "GIT_AUTHOR_EMAIL", opts.Author.Email)
+	}
+	if opts.AuthorDate != "" {
+		cmd.Env = setEnv(cmd.Env, "GIT_AUTHOR_DATE", opts.AuthorDate)
+	}
+	if opts.Committer.Name != "" {
+		cmd.Env = setEnv(cmd.Env, "GIT_COMMITTER_NAME", opts.Committer.Name)
+	}
+	if opts.Committer.Email != "" {
+		cmd.Env = setEnv(cmd.Env, "GIT_COMMITTER_EMAIL", opts.Committer.Email)
+	}
+	if opts.CommitterDate != "" {
+		cmd.Env = setEnv(cmd.Env, "GIT_COMMITTER_DATE", opts.CommitterDate)
+	}
 
-	stdout, err := repo.Run(tb, nil, "git", args...)
+	stdout, err := cmd.Output()
 	if err != nil {
 		return id.ObjectID{}, fmt.Errorf("commit-tree: %w", err)
 	}