Treat incomplete remote tag observations as uncertain

internal/git/remote.go

@@ -43,7 +43,7 @@ const (
 )
 
 // RemoteRef holds an exact ref's object and optional peeled commit. State is
-// RefConflict only when more than one exact result or malformed data is found.
+// RefConflict when records are inconsistent or incomplete.
 type RemoteRef struct {
 	State  RefState
 	Object string
@@ -130,7 +130,7 @@ func (endpoint Endpoint) Query(ctx context.Context, repositoryDir, tag string) (
 			remoteTag = mergeRef(remoteTag, object, true)
 		}
 	}
-	return Snapshot{Main: main, Tag: remoteTag}, nil
+	return Snapshot{Main: main, Tag: finalizeRef(remoteTag)}, nil
 }
 
 // RequireCandidate requires exact main equality and an absent remote
@@ -294,6 +294,13 @@ func mergeRef(ref RemoteRef, object string, peeled bool) RemoteRef {
 	return ref
 }
 
+func finalizeRef(ref RemoteRef) RemoteRef {
+	if ref.State == RefPresent && ref.Object == "" && ref.Peeled != "" {
+		ref.State = RefConflict
+	}
+	return ref
+}
+
 func checkTagRef(ctx context.Context, repositoryDir, tag string) error {
 	if tag == "" {
 		return fmt.Errorf("invalid Git tag name %q", tag)

internal/git/remote_test.go

@@ -184,6 +184,52 @@ func TestMergeRefMarksDuplicateExactResultsConflicting(t *testing.T) {
 	}
 }
 
+func TestTagQueryFinalizesCompleteResponse(t *testing.T) {
+	repo := newRemoteFixture(t)
+	endpoint := resolveFixture(t, repo)
+	realGit, err := exec.LookPath("git")
+	if err != nil {
+		t.Fatal(err)
+	}
+	bin := t.TempDir()
+	response := filepath.Join(t.TempDir(), "response")
+	script := "#!/bin/sh\ncase \" $* \" in *' ls-remote '* ) case \" $* \" in *' --get-url '* ) ;; *) cat \"$RESPONSE\"; exit 0;; esac;; esac\nexec \"$REAL_GIT\" \"$@\"\n"
+	if err := os.WriteFile(filepath.Join(bin, "git"), []byte(script), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	t.Setenv("PATH", bin+string(os.PathListSeparator)+os.Getenv("PATH"))
+	t.Setenv("REAL_GIT", realGit)
+	t.Setenv("RESPONSE", response)
+	object, peeled := strings.Repeat("a", 40), strings.Repeat("b", 40)
+	exact := object + "\trefs/tags/v1.2.3\n"
+	peel := peeled + "\trefs/tags/v1.2.3^{}\n"
+	for _, tc := range []struct {
+		name, output string
+		want         RemoteRef
+	}{
+		{"empty", "", RemoteRef{State: RefAbsent}},
+		{"exact", exact, RemoteRef{State: RefPresent, Object: object}},
+		{"exact then peeled", exact + peel, RemoteRef{State: RefPresent, Object: object, Peeled: peeled}},
+		{"peeled then exact", peel + exact, RemoteRef{State: RefPresent, Object: object, Peeled: peeled}},
+		{"peeled only", peel, RemoteRef{State: RefConflict, Peeled: peeled}},
+		{"duplicate", exact + exact, RemoteRef{State: RefConflict, Object: object}},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			if err := os.WriteFile(response, []byte(tc.output), 0o600); err != nil {
+				t.Fatal(err)
+			}
+			snapshot, err := endpoint.Query(context.Background(), repo.work, "v1.2.3")
+			if err != nil || snapshot.Tag != tc.want {
+				t.Fatalf("Query tag = %#v, error = %v, want %#v", snapshot.Tag, err, tc.want)
+			}
+			got, err := endpoint.QueryTag(context.Background(), repo.work, "v1.2.3")
+			if err != nil || got != tc.want {
+				t.Fatalf("QueryTag = %#v, error = %v, want %#v", got, err, tc.want)
+			}
+		})
+	}
+}
+
 type remoteFixture struct {
 	work   string
 	bare   string

internal/git/tag.go

@@ -124,7 +124,7 @@ func (endpoint Endpoint) QueryTag(ctx context.Context, repositoryDir, tag string
 			remoteTag = mergeRef(remoteTag, object, true)
 		}
 	}
-	return remoteTag, nil
+	return finalizeRef(remoteTag), nil
 }
 
 // PushTag publishes only the captured tag object to its exact tag ref.