Snippets: Add more use-cases

- Restored removed built-in snippets.
- Revert a built-in snippet.
- Reset the snippets collection.

src/plugins/texteditor/snippets/snippetscollection.h

@@ -76,10 +76,14 @@ public:
     Hint computeReplacementHint(int index, const Snippet &snippet, Snippet::Group group);
 
     void removeSnippet(int index, Snippet::Group group);
+    void restoreRemovedSnippets(Snippet::Group group);
 
     void setSnippetContent(int index, Snippet::Group group, const QString &content);
 
     const Snippet &snippet(int index, Snippet::Group group) const;
+    Snippet revertedSnippet(int index, Snippet::Group group) const;
+
+    void reset(Snippet::Group group);
 
     int totalActiveSnippets(Snippet::Group group) const;
     int totalSnippets(Snippet::Group group) const;
@@ -89,9 +93,10 @@ public:
 
 private:
     void clear();
+    void clear(Snippet::Group group);
     void updateActiveSnippetsEnd(Snippet::Group group);
 
-    static QList<Snippet> readXML(const QString &fileName);
+    static QList<Snippet> readXML(const QString &fileName, const QString &snippetId = QString());
     static void writeSnippetXML(const Snippet &snippet, QXmlStreamWriter *writer);
 
     static const QLatin1String kSnippet;
@@ -103,9 +108,15 @@ private:
     static const QLatin1String kRemoved;
     static const QLatin1String kModified;
 
+    // Snippets for each group are kept in a list. However, not all of them are necessarily
+    // active. Specifically, removed built-in snippets are kept as the last ones (for each
+    // group there is a iterator that marks the logical end).
     QVector<QList<Snippet> > m_snippets;
     QVector<QList<Snippet>::iterator> m_activeSnippetsEnd;
 
+    // Built-in snippets are specified in an XML embedded as a resource. Snippets created/
+    // modified/removed by the user are stored in another XML created dynamically in the
+    // user's folder.
     QString m_builtInSnippetsPath;
     QString m_userSnippetsPath;
     QString m_snippetsFileName;