Logging: apply filter to glib messages

Traditionally, glib messages were caught via LogRedirect.
Later, they got redirected by installing a handler. That change
disabled the message filtering for known harmless error messages
in LogRedirect, which caused messages from folks to show up
in TestCmdline D-Bus tests randomly, depending on the timing.

Reestablish the filtering by checking it in the glog callback.
To minimize changes, keep the error registry in LogRedirect.
It must be thread-safe now.

src/syncevo/LogRedirect.cpp

@@ -534,8 +534,15 @@ bool LogRedirect::process(FDs &fds) throw()
     return data_read;
 }
 
+void LogRedirect::addIgnoreError(const std::string &error)
+{
+    RecMutex::Guard guard = Logger::lock();
+    m_knownErrors.insert(error);
+}
+
 bool LogRedirect::ignoreError(const std::string &text)
 {
+    RecMutex::Guard guard = Logger::lock();
     BOOST_FOREACH(const std::string &entry, m_knownErrors) {
         if (text.find(entry) != text.npos) {
             return true;

src/syncevo/LogRedirect.h

@@ -99,7 +99,15 @@ class LogRedirect : public LoggerStdout
     };
 
     /** ignore any error output containing "error" */
-    static void addIgnoreError(const std::string &error) { m_knownErrors.insert(error); }
+    static void addIgnoreError(const std::string &error);
+
+    /**
+     * Messages containing text listed in
+     * SYNCEVOLUTION_SUPPRESS_ERRORS env variable (new-line separated)
+     * or registered via addIgnoreError() are not real errors and
+     * should only be logged for developers.
+     */
+    static bool ignoreError(const std::string &text);
 
  private:
     FDs m_stdout, m_stderr;
@@ -122,13 +130,6 @@ class LogRedirect : public LoggerStdout
     bool process(FDs &fds) throw();
     static void abortHandler(int sig) throw();
 
-    /**
-     * ignore error messages containing text listed in
-     * SYNCEVOLUTION_SUPPRESS_ERRORS env variable (new-line
-     * separated)
-     */
-    bool ignoreError(const std::string &text);
-
     void init();
 
  public:

src/syncevo/Logging.cpp

@@ -20,6 +20,7 @@
 
 #include <syncevo/Logging.h>
 #include <syncevo/LogStdout.h>
+#include <syncevo/LogRedirect.h>
 
 #include <vector>
 #include <string.h>
@@ -369,10 +370,21 @@ void Logger::glogFunc(const gchar *logDomain,
                       const gchar *message,
                       gpointer userData)
 {
-    Logger::instance().message((logLevel & (G_LOG_LEVEL_ERROR|G_LOG_LEVEL_CRITICAL)) ? ERROR :
-                               (logLevel & G_LOG_LEVEL_WARNING) ? WARNING :
-                               (logLevel & (G_LOG_LEVEL_MESSAGE|G_LOG_LEVEL_INFO)) ? SHOW :
-                               DEBUG,
+    Level level =
+        (logLevel & (G_LOG_LEVEL_ERROR|G_LOG_LEVEL_CRITICAL)) ? ERROR :
+        (logLevel & G_LOG_LEVEL_WARNING) ? WARNING :
+        (logLevel & (G_LOG_LEVEL_MESSAGE|G_LOG_LEVEL_INFO)) ? SHOW :
+        DEBUG;
+
+    // Downgrade some know error messages as registered with
+    // the LogRedirect helper class. That messages are registered
+    // there is a historic artifact.
+    if (level != DEBUG &&
+        LogRedirect::ignoreError(message)) {
+        level = DEBUG;
+    }
+
+    Logger::instance().message(level,
                                NULL,
                                NULL,
                                0,