refactor commit interface to pass more information around

---
type: change
message: refactor commit interface to pass more information around
change_hash: AIZfiSAG5eOrh4UUXaAaHLpEtmhgLwhKj5GrReujp/dO
credentials:
- type: pgp_signature
  pub_key_id: 95C46FA6A41148AC
  body: 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
  account: mediocregopher

commit.go

@@ -10,6 +10,7 @@ import (
 	"encoding/base64"
 	"errors"
 	"fmt"
+	"sort"
 	"time"
 
 	"gopkg.in/src-d/go-git.v4"
@@ -22,7 +23,9 @@ import (
 // different commit types.
 type CommitInterface interface {
 	// MessageHead returns the head of the commit message (i.e. the first line).
-	MessageHead() (string, error)
+	// The CommitCommon of the outer Commit is passed in for added context, if
+	// necessary.
+	MessageHead(CommitCommon) (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
@@ -36,15 +39,33 @@ type CommitInterface interface {
 	GetHash() []byte
 }
 
+// CommitCommon describes the fields common to all Commit objects.
+type CommitCommon struct {
+	// 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"`
+}
+
+func (cc CommitCommon) credAccountIDs() []string {
+	m := map[string]struct{}{}
+	for _, cred := range cc.Credentials {
+		m[cred.AccountID] = struct{}{}
+	}
+	s := make([]string, 0, len(m))
+	for accountID := range m {
+		s = append(s, accountID)
+	}
+	sort.Strings(s)
+	return s
+}
+
 // 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"`
 	Credential *CommitCredential `type:"credential"`
 
-	// Credentials represent all created Credentials for this commit, and can be
+	Common CommitCommon `yaml:",inline"`
-	// set on all Commit objects regardless of other fields being set.
-	Credentials []sigcred.Credential `yaml:"credentials"`
 }
 
 // MarshalYAML implements the yaml.Marshaler interface.
@@ -84,7 +105,7 @@ func (c Commit) MarshalText() ([]byte, error) {
 		return nil, fmt.Errorf("could not cast Commit %+v to interface : %w", c, err)
 	}
 
-	msgHead, err := commitInt.MessageHead()
+	msgHead, err := commitInt.MessageHead(c.Common)
 	if err != nil {
 		return nil, fmt.Errorf("error constructing message head: %w", err)
 	}
@@ -133,7 +154,7 @@ func (r *Repo) AccreditCommit(commit Commit, sigInt sigcred.SignifierInterface)
 	if err != nil {
 		return commit, fmt.Errorf("could not accredit change commit: %w", err)
 	}
-	commit.Credentials = append(commit.Credentials, cred)
+	commit.Common.Credentials = append(commit.Common.Credentials, cred)
 	return commit, nil
 }
 
@@ -241,7 +262,7 @@ func (r *Repo) assertAccessControls(
 	return accessctl.AssertCanCommit(acl, accessctl.CommitRequest{
 		Type:         commitType,
 		Branch:       branch.Short(),
-		Credentials:  commit.Credentials,
+		Credentials:  commit.Common.Credentials,
 		FilesChanged: pathsChanged,
 	})
 }
@@ -318,7 +339,7 @@ func (r *Repo) verifyCommit(branch plumbing.ReferenceName, gitCommit GitCommit,
 			base64.StdEncoding.EncodeToString(changeHash))
 	}
 
-	for _, cred := range gitCommit.Commit.Credentials {
+	for _, cred := range gitCommit.Commit.Common.Credentials {
 		sig, err := r.signifierForCredential(sigFS, cred)
 		if err != nil {
 			return fmt.Errorf("finding signifier for credential %+v: %w", cred, err)

commit_change.go

@@ -45,7 +45,7 @@ func (r *Repo) NewCommitChange(msg string) (Commit, error) {
 }
 
 // MessageHead implements the method for the CommitInterface interface.
-func (cc CommitChange) MessageHead() (string, error) {
+func (cc CommitChange) MessageHead(CommitCommon) (string, error) {
 	i := strings.Index(cc.Message, "\n")
 	if i > 0 {
 		return cc.Message[:i], nil

commit_credential.go

@@ -4,6 +4,7 @@ import (
 	"dehub/yamlutil"
 	"encoding/base64"
 	"fmt"
+	"strings"
 
 	"gopkg.in/src-d/go-git.v4/plumbing/object"
 )
@@ -27,12 +28,14 @@ func (r *Repo) NewCommitCredential(hash []byte) (Commit, error) {
 }
 
 // MessageHead implements the method for the CommitInterface interface.
-func (cc CommitCredential) MessageHead() (string, error) {
+func (cc CommitCredential) MessageHead(common CommitCommon) (string, error) {
 	hash64 := base64.StdEncoding.EncodeToString(cc.CredentialedHash)
 	if len(hash64) > 6 {
 		hash64 = hash64[:6] + "..."
 	}
-	return fmt.Sprintf("Credential of hash %s", hash64), nil
+
+	credAccounts := strings.Join(common.credAccountIDs(), ", ")
+	return fmt.Sprintf("Credential of hash %s by %s", hash64, credAccounts), nil
 }
 
 // Hash implements the method for the CommitInterface.