libgit2: add remaining checkout strategy tests

This commit is a follow up on 4dc3185
and adds tests for the remaining checkout strategies, while
consolidating some of the logic.

Signed-off-by: Hidde Beydals <hello@hidde.co>

pkg/git/libgit2/checkout.go

@@ -98,31 +98,12 @@ func (c *CheckoutTag) Checkout(ctx context.Context, path, url string, auth *git.
 		},
 	})
 	if err != nil {
-		return nil, "", fmt.Errorf("unable to clone '%s', error: %w", url, err)
-	}
-	ref, err := repo.References.Dwim(c.tag)
-	if err != nil {
-		return nil, "", fmt.Errorf("unable to find tag '%s': %w", c.tag, err)
-	}
-	err = repo.SetHeadDetached(ref.Target())
-	if err != nil {
-		return nil, "", fmt.Errorf("git checkout error: %w", err)
-	}
-	head, err := repo.Head()
-	if err != nil {
-		return nil, "", fmt.Errorf("git resolve HEAD error: %w", err)
+		return nil, "", fmt.Errorf("unable to clone '%s', error: %w", url, gitutil.LibGit2Error(err))
 	}
-	commit, err := repo.LookupCommit(head.Target())
+	commit, err := checkoutRef(repo, c.tag)
 	if err != nil {
-		return nil, "", fmt.Errorf("git commit '%s' not found: %w", head.Target(), err)
-	}
-	err = repo.CheckoutHead(&git2go.CheckoutOptions{
-		Strategy: git2go.CheckoutForce,
-	})
-	if err != nil {
-		return nil, "", fmt.Errorf("git checkout error: %w", err)
+		return nil, "", err
 	}
-
 	return &Commit{commit}, fmt.Sprintf("%s/%s", c.tag, commit.Id().String()), nil
 }
 
@@ -140,30 +121,19 @@ func (c *CheckoutCommit) Checkout(ctx context.Context, path, url string, auth *g
 				CertificateCheckCallback: auth.CertCallback,
 			},
 		},
-		CheckoutBranch: c.branch,
 	})
 	if err != nil {
-		return nil, "", fmt.Errorf("unable to clone '%s', error: %w", url, err)
+		return nil, "", fmt.Errorf("unable to clone '%s', error: %w", url, gitutil.LibGit2Error(err))
 	}
+
 	oid, err := git2go.NewOid(c.commit)
 	if err != nil {
-		return nil, "", fmt.Errorf("git commit '%s' could not be parsed", c.commit)
-	}
-	commit, err := repo.LookupCommit(oid)
-	if err != nil {
-		return nil, "", fmt.Errorf("git commit '%s' not found: %w", c.commit, err)
-	}
-	tree, err := repo.LookupTree(commit.TreeId())
-	if err != nil {
-		return nil, "", fmt.Errorf("git worktree error: %w", err)
+		return nil, "", fmt.Errorf("could not create oid for '%s': %w", c.commit, err)
 	}
-	err = repo.CheckoutTree(tree, &git2go.CheckoutOptions{
-		Strategy: git2go.CheckoutForce,
-	})
+	commit, err := checkoutCommit(repo, oid)
 	if err != nil {
 		return nil, "", fmt.Errorf("git checkout error: %w", err)
 	}
-
 	return &Commit{commit}, fmt.Sprintf("%s/%s", c.branch, commit.Id().String()), nil
 }
 
@@ -187,7 +157,7 @@ func (c *CheckoutSemVer) Checkout(ctx context.Context, path, url string, auth *g
 		},
 	})
 	if err != nil {
-		return nil, "", fmt.Errorf("unable to clone '%s', error: %w", url, err)
+		return nil, "", fmt.Errorf("unable to clone '%s', error: %w", url, gitutil.LibGit2Error(err))
 	}
 
 	tags := make(map[string]string)
@@ -255,28 +225,58 @@ func (c *CheckoutSemVer) Checkout(ctx context.Context, path, url string, auth *g
 	v := matchedVersions[len(matchedVersions)-1]
 	t := v.Original()
 
-	ref, err := repo.References.Dwim(t)
+	commit, err := checkoutRef(repo, t)
+	return &Commit{commit}, fmt.Sprintf("%s/%s", t, commit.Id().String()), nil
+}
+
+func checkoutRef(repo *git2go.Repository, name string) (*git2go.Commit, error) {
+	ref, err := repo.References.Dwim(name)
 	if err != nil {
-		return nil, "", fmt.Errorf("unable to find tag '%s': %w", t, err)
+		return nil, fmt.Errorf("unable to find '%s': %w", name, err)
 	}
-	err = repo.SetHeadDetached(ref.Target())
+	defer ref.Free()
+	c, err := ref.Peel(git2go.ObjectCommit)
 	if err != nil {
-		return nil, "", fmt.Errorf("git checkout error: %w", err)
+		return nil, fmt.Errorf("could not get commit for ref '%s': %w", ref.Name(), err)
 	}
-	head, err := repo.Head()
+	defer c.Free()
+	commit, err := c.AsCommit()
 	if err != nil {
-		return nil, "", fmt.Errorf("git resolve HEAD error: %w", err)
+		return nil, fmt.Errorf("could not get commit object for ref '%s': %w", ref.Name(), err)
 	}
-	commit, err := repo.LookupCommit(head.Target())
+	defer commit.Free()
+	return checkoutCommit(repo, commit.Id())
+}
+
+func checkoutCommit(repo *git2go.Repository, oid *git2go.Oid) (*git2go.Commit, error) {
+	commit, err := repo.LookupCommit(oid)
 	if err != nil {
-		return nil, "", fmt.Errorf("git commit '%s' not found: %w", head.Target().String(), err)
+		return nil, fmt.Errorf("git commit '%s' not found: %w", oid.String(), err)
 	}
-	err = repo.CheckoutHead(&git2go.CheckoutOptions{
+	if err = repo.SetHeadDetached(commit.Id()); err != nil {
+		commit.Free()
+		return nil, fmt.Errorf("could not detach HEAD at '%s': %w", oid.String(), err)
+	}
+	if err = repo.CheckoutHead(&git2go.CheckoutOptions{
 		Strategy: git2go.CheckoutForce,
-	})
+	}); err != nil {
+		commit.Free()
+		return nil, fmt.Errorf("git checkout error: %w", err)
+	}
+	return commit, nil
+}
+
+func headCommit(repo *git2go.Repository) (*git2go.Commit, error) {
+	head, err := repo.Head()
 	if err != nil {
-		return nil, "", fmt.Errorf("git checkout error: %w", err)
+		return nil, err
 	}
+	defer head.Free()
 
-	return &Commit{commit}, fmt.Sprintf("%s/%s", t, commit.Id().String()), nil
+	commit, err := repo.LookupCommit(head.Target())
+	if err != nil {
+		return nil, err
+	}
+
+	return commit, nil
 }