Add explicit

src/musicbrainz/acoustidclient.h

@@ -33,7 +33,6 @@ class QNetworkReply;
 class NetworkTimeouts;
 
 class AcoustidClient : public QObject {
-
   Q_OBJECT
 
   // Gets a MBID from a Chromaprint fingerprint.
@@ -43,7 +42,7 @@ class AcoustidClient : public QObject {
   // IDs are provided by the caller when a request is started and included in the Finished signal - they have no meaning to AcoustidClient.
 
  public:
-  AcoustidClient(QObject *parent = nullptr);
+  explicit AcoustidClient(QObject *parent = nullptr);
 
   // Network requests will be aborted after this interval.
   void SetTimeout(const int msec);

src/musicbrainz/chromaprinter.h

@@ -38,7 +38,7 @@ class Chromaprinter {
   // This class works well with QtConcurrentMap.
 
  public:
-  Chromaprinter(const QString &filename);
+  explicit Chromaprinter(const QString &filename);
   ~Chromaprinter();
 
   // Creates a fingerprint from the song.

src/musicbrainz/musicbrainzclient.h

@@ -50,7 +50,7 @@ class MusicBrainzClient : public QObject {
  public:
   // The second argument allows for specifying a custom network access manager.
   // It is used in tests. The ownership of network is not transferred.
-  MusicBrainzClient(QObject *parent = nullptr, QNetworkAccessManager *network = nullptr);
+  explicit MusicBrainzClient(QObject *parent = nullptr, QNetworkAccessManager *network = nullptr);
 
   struct Result {
     Result() : duration_msec_(0), track_(0), year_(-1) {}

src/musicbrainz/tagfetcher.h

@@ -39,7 +39,7 @@ class TagFetcher : public QObject {
   // High level interface to Fingerprinter, AcoustidClient and MusicBrainzClient.
 
  public:
-  TagFetcher(QObject *parent = nullptr);
+  explicit TagFetcher(QObject *parent = nullptr);
 
   void StartFetch(const SongList &songs);