Add reusable CI preparation operations

internal/preparation/preparation.go

@@ -0,0 +1,43 @@
+// Package preparation coordinates explicit local checkout and Go module
+// preparation operations for consumers and CI adapters.
+package preparation
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"strings"
+
+	"gitea.maximumdirect.net/eric/ReleaseKit/internal/candidate"
+	"gitea.maximumdirect.net/eric/ReleaseKit/internal/git"
+	"gitea.maximumdirect.net/eric/ReleaseKit/internal/gotool"
+	"gitea.maximumdirect.net/eric/ReleaseKit/internal/versioncontract"
+)
+
+type TaggedCheckoutRequest struct {
+	RepositoryDir  string
+	Version        string
+	Remote         string
+	ExpectedCommit string
+}
+
+func PrepareTaggedCheckout(ctx context.Context, request TaggedCheckoutRequest) error {
+	if !versioncontract.ValidStableVersion(request.Version) {
+		return fmt.Errorf("%w: %q", candidate.ErrInvalidVersion, request.Version)
+	}
+	if strings.TrimSpace(request.ExpectedCommit) == "" {
+		return errors.New("expected commit is required")
+	}
+	remote := request.Remote
+	if remote == "" {
+		remote = "origin"
+	}
+	return git.PrepareTaggedCheckout(ctx, request.RepositoryDir, request.Version, remote, request.ExpectedCommit)
+}
+
+func PrepareBuildDependencies(ctx context.Context, repositoryDir string) error {
+	if strings.TrimSpace(repositoryDir) == "" {
+		return errors.New("repository directory is required")
+	}
+	return gotool.PrepareBuildDependencies(ctx, repositoryDir)
+}