Refactor commit type and logic to account for future commit types

---
type: change
message: |-
  Refactor commit type and logic to account for future commit types

  This commit introduces a CommitInterface which CommitChange (previously
  ChangeCommit) now implements. Additionally, now all commit messages will include
  a type field and a "---" separator. The code is written to still accept all the
  old commit messages used in this repo. Other than those changes, most of this is
  just rearranging existing code.
change_hash: AHjWAUxCjXgOL0Sb+oQZc6TmuVgVHJn08zpGreYyChwx
credentials:
- type: pgp_signature
  pub_key_id: 95C46FA6A41148AC
  body: 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
  account: mediocregopher

ROADMAP.md

@@ -20,6 +20,9 @@ set, only a sequence of milestones and the requirements to hit them.
 
 ## Milestone: Enough polish to show off the project
 
+* Maybe coalesce the `accessctl`, `fs`, and `sigcred` packages back into the
+  root "dehub" package.
+
 * Polish commands
     - New flag system, some kind of interactivity support (e.g. user doesn't
       specify required argument, give them a prompt on the CLI to input it

cmd/dehub/main.go

@@ -155,12 +155,17 @@ var subCmds = []subCmd{
 				return fmt.Errorf("could not cast %+v to SignifierInterface: %w", sig, err)
 			}
 
-			tc, err := sctx.repo().NewChangeCommit(*msg, *accountID, sigInt)
+			commit, err := sctx.repo().NewCommitChange(*msg)
 			if err != nil {
 				return fmt.Errorf("could not construct change commit: %w", err)
 			}
 
-			hash, err := sctx.repo().Commit(tc, *accountID)
+			commit, err = sctx.repo().AccreditCommit(commit, *accountID, sigInt)
+			if err != nil {
+				return fmt.Errorf("could not accredit commit: %w", err)
+			}
+
+			hash, err := sctx.repo().Commit(commit, *accountID)
 			if err != nil {
 				return fmt.Errorf("could not commit change commit: %w", err)
 			}
@@ -191,7 +196,7 @@ var subCmds = []subCmd{
 				branchName = plumbing.NewBranchReferenceName(*branch)
 			}
 
-			if err := sctx.repo().VerifyChangeCommit(branchName, *h); err != nil {
+			if err := sctx.repo().VerifyCommit(branchName, *h); err != nil {
 				return fmt.Errorf("could not verify commit at %q (%s): %w", *rev, *h, err)
 			}
 
@@ -278,7 +283,7 @@ var subCmds = []subCmd{
 				for i := len(hashesToCheck) - 1; i >= 0; i-- {
 					hash := hashesToCheck[i]
 					fmt.Printf("Verifying change commit %q\n", hash)
-					if err := sctx.repo().VerifyChangeCommit(branchName, hash); err != nil {
+					if err := sctx.repo().VerifyCommit(branchName, hash); err != nil {
 						return fmt.Errorf("could not verify change commit %q: %w", hash, err)
 					}
 				}

commit.go

@@ -5,10 +5,9 @@ import (
 	"dehub/accessctl"
 	"dehub/fs"
 	"dehub/sigcred"
-	"dehub/yamlutil"
+	"dehub/typeobj"
 	"encoding"
 	"encoding/base64"
-	"errors"
 	"fmt"
 	"strings"
 	"time"
@@ -19,57 +18,114 @@ import (
 	yaml "gopkg.in/yaml.v2"
 )
 
-// ChangeCommit describes the structure of a change commit message.
-type ChangeCommit struct {
-	Message     string               `yaml:"message"`
-	ChangeHash  yamlutil.Blob        `yaml:"change_hash"`
+// CommitInterface describes the methods which must be implemented by the
+// different commit types.
+type CommitInterface interface {
+	// MessageHead returns the head of the commit message (i.e. the first line).
+	MessageHead() (string, error)
+
+	// Hash returns the raw hash which Signifiers can sign to accredit this
+	// commit. The tree objects given describe the filesystem state of the
+	// parent commit, and the filesystem state of this commit.
+	//
+	// This method should _not_ change any fields on the commit.
+	Hash(parent, this *object.Tree) ([]byte, error)
+
+	// GetHash returns the signable Hash embedded in the commit, which should
+	// hopefully correspond to the Commit's Credentials.
+	GetHash() []byte
+}
+
+// Commit represents a single Commit which is being added to a branch. Only one
+// field should be set on a Commit, unless otherwise noted.
+type Commit struct {
+	Change *CommitChange `type:"change,default"`
+
+	// Credentials represent all created Credentials for this commit, and can be
+	// set on all Commit objects regardless of other fields being set.
 	Credentials []sigcred.Credential `yaml:"credentials"`
 }
 
-type ccYAML struct {
-	Val ChangeCommit `yaml:",inline"`
+// MarshalYAML implements the yaml.Marshaler interface.
+func (c Commit) MarshalYAML() (interface{}, error) {
+	return typeobj.MarshalYAML(c)
 }
 
-func msgHead(msg string) string {
-	i := strings.Index(msg, "\n")
-	if i > 0 {
-		return msg[:i]
+// UnmarshalYAML implements the yaml.Unmarshaler interface.
+func (c *Commit) UnmarshalYAML(unmarshal func(interface{}) error) error {
+	return typeobj.UnmarshalYAML(c, unmarshal)
+}
+
+// Interface returns the CommitInterface instance encapsulated by this Commit
+// object.
+func (c Commit) Interface() (CommitInterface, error) {
+	el, _, err := typeobj.Element(c)
+	if err != nil {
+		return nil, err
 	}
-	return msg
+	return el.(CommitInterface), nil
 }
 
 // MarshalText implements the encoding.TextMarshaler interface by returning the
-// form the ChangeCommit object takes in the git commit message.
-func (cc ChangeCommit) MarshalText() ([]byte, error) {
-	changeCommitEncoded, err := yaml.Marshal(ccYAML{cc})
+// form the Commit object takes in the git commit message.
+func (c Commit) MarshalText() ([]byte, error) {
+	commitInt, err := c.Interface()
+	if err != nil {
+		return nil, fmt.Errorf("could not cast Commit %+v to interface : %w", c, err)
+	}
+
+	msgHead, err := commitInt.MessageHead()
+	if err != nil {
+		return nil, fmt.Errorf("error constructing message head: %w", err)
+	}
+
+	msgBodyB, err := yaml.Marshal(c)
 	if err != nil {
-		return nil, fmt.Errorf("failed to encode ChangeCommit message: %w", err)
+		return nil, fmt.Errorf("error marshaling commit %+v as yaml: %w", c, err)
 	}
 
-	fullMsg := msgHead(cc.Message) + "\n\n" + string(changeCommitEncoded)
-	return []byte(fullMsg), nil
+	w := new(bytes.Buffer)
+	w.WriteString(msgHead)
+	w.WriteString("\n\n---\n")
+	w.Write(msgBodyB)
+	return w.Bytes(), nil
 }
 
 // UnmarshalText implements the encoding.TextUnmarshaler interface by decoding a
-// ChangeCommit object which has been encoded into a git commit message.
-func (cc *ChangeCommit) UnmarshalText(msg []byte) error {
+// Commit object which has been encoded into a git commit message.
+func (c *Commit) UnmarshalText(msg []byte) error {
 	i := bytes.Index(msg, []byte("\n"))
 	if i < 0 {
-		return fmt.Errorf("commit message %q is malformed", msg)
+		return fmt.Errorf("commit message %q is malformed, it has no body", msg)
 	}
-	msgHead, msg := msg[:i], msg[i:]
+	msgBody := msg[i:]
 
-	var ccy ccYAML
-	if err := yaml.Unmarshal(msg, &ccy); err != nil {
-		return fmt.Errorf("could not unmarshal ChangeCommit message: %w", err)
+	if err := yaml.Unmarshal(msgBody, c); err != nil {
+		return fmt.Errorf("could not unmarshal Commit message from yaml: %w", err)
 	}
+	return nil
+}
 
-	*cc = ccy.Val
-	if !strings.HasPrefix(cc.Message, string(msgHead)) {
-		return errors.New("encoded ChangeCommit is malformed, it might not be an encoded ChangeCommit")
+// AccreditCommit returns the given Commit with an appended Credential provided
+// by the given account and its Signifier.
+func (r *Repo) AccreditCommit(commit Commit, accountID string, sigInt sigcred.SignifierInterface) (Commit, error) {
+	commitInt, err := commit.Interface()
+	if err != nil {
+		return commit, fmt.Errorf("could not cast commit %+v to interface: %w", commit, err)
 	}
 
-	return nil
+	headFS, err := r.HeadFS()
+	if err != nil {
+		return commit, fmt.Errorf("could not grab snapshot of HEAD fs: %w", err)
+	}
+
+	cred, err := sigInt.Sign(headFS, commitInt.GetHash())
+	if err != nil {
+		return commit, fmt.Errorf("could not accreddit change commit: %w", err)
+	}
+	cred.AccountID = accountID
+	commit.Credentials = append(commit.Credentials, cred)
+	return commit, nil
 }
 
 // Commit uses the given TextMarshaler to create a git commit object (with the
@@ -116,50 +172,6 @@ func (r *Repo) HasStagedChanges() (bool, error) {
 	return any, nil
 }
 
-// NewChangeCommit constructs a ChangeCommit. If sig is given then it is used to
-// create a Credential for the ChangeCommit.
-func (r *Repo) NewChangeCommit(msg, accountID string, sig sigcred.SignifierInterface) (ChangeCommit, error) {
-	_, headTree, err := r.head()
-	if errors.Is(err, plumbing.ErrReferenceNotFound) {
-		headTree = &object.Tree{}
-	} else if err != nil {
-		return ChangeCommit{}, err
-	}
-
-	_, stagedTree, err := fs.FromStagedChangesTree(r.GitRepo)
-	if err != nil {
-		return ChangeCommit{}, err
-	}
-
-	changeHash := genChangeHash(nil, msg, headTree, stagedTree)
-
-	var creds []sigcred.Credential
-	if sig != nil {
-		// this is necessarily different than headTree for the case of there
-		// being no HEAD (ie it's the first commit). In that case we want
-		// headTree to be empty (because it's being used to generate the change
-		// hash), but we want the signifier to use the raw fs (because that's
-		// where the signifier's data might be).
-		sigFS, err := r.headOrRawFS()
-		if err != nil {
-			return ChangeCommit{}, err
-		}
-
-		cred, err := sig.Sign(sigFS, changeHash)
-		if err != nil {
-			return ChangeCommit{}, fmt.Errorf("failed to sign commit hash: %w", err)
-		}
-		cred.AccountID = accountID
-		creds = append(creds, cred)
-	}
-
-	return ChangeCommit{
-		Message:     msg,
-		ChangeHash:  changeHash,
-		Credentials: creds,
-	}, nil
-}
-
 func (r *Repo) assertAccessControls(
 	accessCtls []accessctl.BranchAccessControl, creds []sigcred.Credential,
 	branch plumbing.ReferenceName, from, to *object.Tree,
@@ -197,28 +209,23 @@ func (r *Repo) assertAccessControls(
 	return nil
 }
 
-// VerifyChangeCommit verifies that the change commit at the given hash, which
-// is presumably on the given branch, is gucci.
-func (r *Repo) VerifyChangeCommit(branch plumbing.ReferenceName, h plumbing.Hash) error {
-	commit, err := r.GitRepo.CommitObject(h)
+// VerifyCommit verifies that the commit at the given hash, which is presumably
+// on the given branch, is gucci.
+func (r *Repo) VerifyCommit(branch plumbing.ReferenceName, h plumbing.Hash) error {
+	commitObj, err := r.GitRepo.CommitObject(h)
 	if err != nil {
 		return fmt.Errorf("could not retrieve commit object: %w", err)
 	}
 
-	commitTree, err := r.GitRepo.TreeObject(commit.TreeHash)
+	commitTree, err := r.GitRepo.TreeObject(commitObj.TreeHash)
 	if err != nil {
 		return fmt.Errorf("could not retrieve tree object: %w", err)
 	}
 
-	var changeCommit ChangeCommit
-	if err := changeCommit.UnmarshalText([]byte(commit.Message)); err != nil {
-		return err
-	}
-
 	sigTree := commitTree // only for root commit
 	parentTree := &object.Tree{}
-	if commit.NumParents() > 0 {
-		parent, err := commit.Parent(0)
+	if commitObj.NumParents() > 0 {
+		parent, err := commitObj.Parent(0)
 		if err != nil {
 			return fmt.Errorf("could not retrieve parent of commit: %w", err)
 		} else if parentTree, err = r.GitRepo.TreeObject(parent.TreeHash); err != nil {
@@ -228,27 +235,40 @@ func (r *Repo) VerifyChangeCommit(branch plumbing.ReferenceName, h plumbing.Hash
 	}
 	sigFS := fs.FromTree(sigTree)
 
+	var commit Commit
+	if err := commit.UnmarshalText([]byte(commitObj.Message)); err != nil {
+		return err
+	}
+
 	cfg, err := r.loadConfig(sigFS)
 	if err != nil {
 		return fmt.Errorf("error loading config: %w", err)
 	}
 
 	err = r.assertAccessControls(
-		cfg.AccessControls, changeCommit.Credentials,
+		cfg.AccessControls, commit.Credentials,
 		branch, parentTree, commitTree,
 	)
 	if err != nil {
 		return fmt.Errorf("failed to satisfy all access controls: %w", err)
 	}
 
-	expectedChangeHash := genChangeHash(nil, changeCommit.Message, parentTree, commitTree)
-	if !bytes.Equal(changeCommit.ChangeHash, expectedChangeHash) {
+	commitInt, err := commit.Interface()
+	if err != nil {
+		return fmt.Errorf("could not cast commit %+v to interface: %w", commit, err)
+	}
+
+	changeHash := commitInt.GetHash()
+	expectedChangeHash, err := commitInt.Hash(parentTree, commitTree)
+	if err != nil {
+		return fmt.Errorf("error calculating expected change hash: %w", err)
+	} else if !bytes.Equal(changeHash, expectedChangeHash) {
 		return fmt.Errorf("malformed change_hash in commit body, is %s but should be %s",
 			base64.StdEncoding.EncodeToString(expectedChangeHash),
-			base64.StdEncoding.EncodeToString(changeCommit.ChangeHash))
+			base64.StdEncoding.EncodeToString(changeHash))
 	}
 
-	for _, cred := range changeCommit.Credentials {
+	for _, cred := range commit.Credentials {
 		sig, err := r.signifierForCredential(sigFS, cred)
 		if err != nil {
 			return fmt.Errorf("error finding signifier for credential %+v: %w", cred, err)

commit_change.go

@@ -0,0 +1,64 @@
+package dehub
+
+import (
+	"dehub/fs"
+	"dehub/yamlutil"
+	"errors"
+	"strings"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/object"
+)
+
+// CommitChange describes the structure of a change commit message.
+type CommitChange struct {
+	Message    string        `yaml:"message"`
+	ChangeHash yamlutil.Blob `yaml:"change_hash"`
+}
+
+var _ CommitInterface = CommitChange{}
+
+// NewCommitChange constructs a Commit populated with a CommitChange
+// encompassing the currently staged file changes. The Credentials of the
+// returned Commit will _not_ be filled in.
+func (r *Repo) NewCommitChange(msg string) (Commit, error) {
+	_, headTree, err := r.head()
+	if errors.Is(err, plumbing.ErrReferenceNotFound) {
+		headTree = &object.Tree{}
+	} else if err != nil {
+		return Commit{}, err
+	}
+
+	_, stagedTree, err := fs.FromStagedChangesTree(r.GitRepo)
+	if err != nil {
+		return Commit{}, err
+	}
+
+	cc := CommitChange{Message: msg}
+	if cc.ChangeHash, err = cc.Hash(headTree, stagedTree); err != nil {
+		return Commit{}, err
+	}
+
+	return Commit{
+		Change: &cc,
+	}, nil
+}
+
+// MessageHead implements the method for the CommitInterface interface.
+func (cc CommitChange) MessageHead() (string, error) {
+	i := strings.Index(cc.Message, "\n")
+	if i > 0 {
+		return cc.Message[:i], nil
+	}
+	return cc.Message, nil
+}
+
+// Hash implements the method for the CommitInterface interface.
+func (cc CommitChange) Hash(parent, this *object.Tree) ([]byte, error) {
+	return genChangeHash(nil, cc.Message, parent, this), nil
+}
+
+// GetHash implements the method for the CommitInterface interface.
+func (cc CommitChange) GetHash() []byte {
+	return cc.ChangeHash
+}

commit_change_test.go

@@ -0,0 +1,105 @@
+package dehub
+
+import (
+	"reflect"
+	"strings"
+	"testing"
+
+	"github.com/davecgh/go-spew/spew"
+)
+
+func TestChangeCommitVerify(t *testing.T) {
+	type step struct {
+		msg     string
+		msgHead string // defaults to msg
+		tree    map[string]string
+	}
+	testCases := []struct {
+		descr string
+		steps []step
+	}{
+		{
+			descr: "single commit",
+			steps: []step{
+				{
+					msg:  "first commit",
+					tree: map[string]string{"a": "0", "b": "1"},
+				},
+			},
+		},
+		{
+			descr: "multiple commits",
+			steps: []step{
+				{
+					msg:  "first commit",
+					tree: map[string]string{"a": "0", "b": "1"},
+				},
+				{
+					msg:  "second commit, changing a",
+					tree: map[string]string{"a": "1"},
+				},
+				{
+					msg: "third commit, empty",
+				},
+				{
+					msg:  "fourth commit, adding c, removing b",
+					tree: map[string]string{"b": "", "c": "2"},
+				},
+			},
+		},
+		{
+			descr: "big body commits",
+			steps: []step{
+				{
+					msg: "first commit, single line but with newline\n",
+				},
+				{
+					msg:     "second commit, single line but with two newlines\n\n",
+					msgHead: "second commit, single line but with two newlines\n\n",
+				},
+				{
+					msg:     "third commit, multi-line with one newline\nanother line!",
+					msgHead: "third commit, multi-line with one newline\n\n",
+				},
+				{
+					msg:     "fourth commit, multi-line with two newlines\n\nanother line!",
+					msgHead: "fourth commit, multi-line with two newlines\n\n",
+				},
+			},
+		},
+	}
+
+	for _, test := range testCases {
+		t.Run(test.descr, func(t *testing.T) {
+			h := newHarness(t)
+			for _, step := range test.steps {
+				h.stage(step.tree)
+				account := h.cfg.Accounts[0]
+
+				commit, hash := h.changeCommit(step.msg, account.ID, h.sig)
+				if err := h.repo.VerifyCommit(MainRefName, hash); err != nil {
+					t.Fatalf("could not verify hash %v: %v", hash, err)
+				}
+
+				commitObj, err := h.repo.GitRepo.CommitObject(hash)
+				if err != nil {
+					t.Fatalf("failed to retrieve commit %v: %v", hash, err)
+				} else if step.msgHead == "" {
+					step.msgHead = strings.TrimSpace(step.msg) + "\n\n"
+				}
+
+				if !strings.HasPrefix(commitObj.Message, step.msgHead) {
+					t.Fatalf("commit message %q does not start with expected head %q", commitObj.Message, step.msgHead)
+				}
+
+				var actualCommit Commit
+				if err := actualCommit.UnmarshalText([]byte(commitObj.Message)); err != nil {
+					t.Fatalf("error unmarshaling commit body: %v", err)
+				} else if !reflect.DeepEqual(actualCommit, commit) {
+					t.Fatalf("returned change commit:\n%s\ndoes not match actual one:\n%s",
+						spew.Sdump(commit), spew.Sdump(actualCommit))
+				}
+			}
+		})
+	}
+}

commit_test.go

@@ -2,112 +2,13 @@ package dehub
 
 import (
 	"dehub/sigcred"
-	"reflect"
-	"strings"
 	"testing"
 
-	"github.com/davecgh/go-spew/spew"
 	"gopkg.in/src-d/go-git.v4"
 	"gopkg.in/src-d/go-git.v4/plumbing"
 	yaml "gopkg.in/yaml.v2"
 )
 
-func TestChangeCommitVerify(t *testing.T) {
-	type step struct {
-		msg     string
-		msgHead string // defaults to msg
-		tree    map[string]string
-	}
-	testCases := []struct {
-		descr string
-		steps []step
-	}{
-		{
-			descr: "single commit",
-			steps: []step{
-				{
-					msg:  "first commit",
-					tree: map[string]string{"a": "0", "b": "1"},
-				},
-			},
-		},
-		{
-			descr: "multiple commits",
-			steps: []step{
-				{
-					msg:  "first commit",
-					tree: map[string]string{"a": "0", "b": "1"},
-				},
-				{
-					msg:  "second commit, changing a",
-					tree: map[string]string{"a": "1"},
-				},
-				{
-					msg: "third commit, empty",
-				},
-				{
-					msg:  "fourth commit, adding c, removing b",
-					tree: map[string]string{"b": "", "c": "2"},
-				},
-			},
-		},
-		{
-			descr: "big body commits",
-			steps: []step{
-				{
-					msg: "first commit, single line but with newline\n",
-				},
-				{
-					msg:     "second commit, single line but with two newlines\n\n",
-					msgHead: "second commit, single line but with two newlines\n\n",
-				},
-				{
-					msg:     "third commit, multi-line with one newline\nanother line!",
-					msgHead: "third commit, multi-line with one newline\n\n",
-				},
-				{
-					msg:     "fourth commit, multi-line with two newlines\n\nanother line!",
-					msgHead: "fourth commit, multi-line with two newlines\n\n",
-				},
-			},
-		},
-	}
-
-	for _, test := range testCases {
-		t.Run(test.descr, func(t *testing.T) {
-			h := newHarness(t)
-			for _, step := range test.steps {
-				h.stage(step.tree)
-				account := h.cfg.Accounts[0]
-
-				changeCommit, hash := h.changeCommit(step.msg, account.ID, h.sig)
-				if err := h.repo.VerifyChangeCommit(MainRefName, hash); err != nil {
-					t.Fatalf("could not verify hash %v: %v", hash, err)
-				}
-
-				commit, err := h.repo.GitRepo.CommitObject(hash)
-				if err != nil {
-					t.Fatalf("failed to retrieve commit %v: %v", hash, err)
-				} else if step.msgHead == "" {
-					step.msgHead = strings.TrimSpace(step.msg) + "\n\n"
-				}
-
-				if !strings.HasPrefix(commit.Message, step.msgHead) {
-					t.Fatalf("commit message %q does not start with expected head %q", commit.Message, step.msgHead)
-				}
-
-				var actualChangeCommit ChangeCommit
-				if err := actualChangeCommit.UnmarshalText([]byte(commit.Message)); err != nil {
-					t.Fatalf("error unmarshaling commit body: %v", err)
-				} else if !reflect.DeepEqual(actualChangeCommit, changeCommit) {
-					t.Fatalf("returned change commit:\n%s\ndoes not match actual one:\n%s",
-						spew.Sdump(changeCommit), spew.Sdump(actualChangeCommit))
-				}
-			}
-		})
-	}
-}
-
 func TestConfigChange(t *testing.T) {
 	h := newHarness(t)
 
@@ -137,7 +38,7 @@ func TestConfigChange(t *testing.T) {
 	h.stage(map[string]string{ConfigPath: string(cfgBody)})
 	_, badHash := h.changeCommit("add toot user", h.cfg.Accounts[1].ID, newSig)
 
-	if err := h.repo.VerifyChangeCommit(MainRefName, badHash); err == nil {
+	if err := h.repo.VerifyCommit(MainRefName, badHash); err == nil {
 		t.Fatal("toot user shouldn't be able to add itself to config")
 	}
 	h.reset(hash, git.HardReset)
@@ -153,7 +54,7 @@ func TestConfigChange(t *testing.T) {
 	hashes = append(hashes, hash)
 
 	for i, hash := range hashes {
-		if err := h.repo.VerifyChangeCommit(MainRefName, hash); err != nil {
+		if err := h.repo.VerifyCommit(MainRefName, hash); err != nil {
 			t.Fatalf("commit %d (%v) should have been verified but wasn't: %v", i, hash, err)
 		}
 	}

config.go

@@ -44,7 +44,7 @@ func (r *Repo) loadConfig(fs fs.FS) (Config, error) {
 // LoadConfig loads the Config object from the HEAD of the repo, or directly
 // from the filesystem if there is no HEAD yet.
 func (r *Repo) LoadConfig() (Config, error) {
-	headFS, err := r.headOrRawFS()
+	headFS, err := r.HeadFS()
 	if err != nil {
 		return Config{}, fmt.Errorf("error retrieving repo HEAD: %w", err)
 	}

repo.go

@@ -158,9 +158,9 @@ func (r *Repo) head() (*object.Commit, *object.Tree, error) {
 	return headCommit, headTree, nil
 }
 
-// headOrRawFS returns an FS based on the HEAD commit, or if there is no HEAD
-// commit (it's an empty repo) an FS based on the raw filesystem.
-func (r *Repo) headOrRawFS() (fs.FS, error) {
+// HeadFS returns an FS based on the HEAD commit, or if there is no HEAD commit
+// (it's an empty repo) an FS based on the raw filesystem.
+func (r *Repo) HeadFS() (fs.FS, error) {
 	_, headTree, err := r.head()
 	if errors.Is(err, plumbing.ErrReferenceNotFound) {
 		bfs, err := r.billyFilesystem()

repo_test.go

@@ -107,18 +107,24 @@ func (h *harness) stage(tree map[string]string) {
 	}
 }
 
-func (h *harness) changeCommit(msg, accountID string, sig sigcred.SignifierInterface) (ChangeCommit, plumbing.Hash) {
-	tc, err := h.repo.NewChangeCommit(msg, accountID, sig)
+func (h *harness) changeCommit(msg, accountID string, sig sigcred.SignifierInterface) (Commit, plumbing.Hash) {
+	commit, err := h.repo.NewCommitChange(msg)
 	if err != nil {
-		h.t.Fatalf("failed to make ChangeCommit: %v", err)
+		h.t.Fatalf("failed to create CommitChange: %v", err)
 	}
 
-	hash, err := h.repo.Commit(tc, accountID)
+	if sig != nil {
+		if commit, err = h.repo.AccreditCommit(commit, accountID, sig); err != nil {
+			h.t.Fatalf("failed to accredit commit: %v", err)
+		}
+	}
+
+	hash, err := h.repo.Commit(commit, accountID)
 	if err != nil {
 		h.t.Fatalf("failed to commit ChangeCommit: %v", err)
 	}
 
-	return tc, hash
+	return commit, hash
 }
 
 func (h *harness) reset(to plumbing.Hash, mode git.ResetMode) {
@@ -193,9 +199,9 @@ access_controls:
 	_, hash1 := harness.changeCommit("ain't no laws", "toot", nil)
 
 	// verifying the first should work, but not the second.
-	if err := harness.repo.VerifyChangeCommit(MainRefName, hash0); err != nil {
+	if err := harness.repo.VerifyCommit(MainRefName, hash0); err != nil {
 		t.Fatalf("first commit %q should be verifiable, but got: %v", hash0, err)
-	} else if err := harness.repo.VerifyChangeCommit(MainRefName, hash1); err == nil {
+	} else if err := harness.repo.VerifyCommit(MainRefName, hash1); err == nil {
 		t.Fatalf("second commit %q should not have been verified", hash1)
 	}
 
@@ -212,7 +218,7 @@ accounts:
         path: ".dehub/root.asc"
 `})
 	_, hash2 := harness.changeCommit("Fix the config!", "root", harness.sig)
-	if err := harness.repo.VerifyChangeCommit(MainRefName, hash2); err != nil {
+	if err := harness.repo.VerifyCommit(MainRefName, hash2); err != nil {
 		t.Fatalf("config fix commit %q should be verifiable, but got: %v", hash2, err)
 	}
 }