libmblog: Shorten tag by default

Signed-off-by: Andrew Gunnerson <[email protected]>

libmblog/src/logging.cpp

@@ -66,11 +66,12 @@ using Tid = pid_t;
 static std::shared_ptr<BaseLogger> g_logger;
 static std::mutex g_mutex;
 
-static std::string g_format{"[%t][%P:%T][%l] %n: %m"};
+static std::string g_format{"[%t][%P:%T][%l] %N: %m"};
 
 // %l - Level
 // %m - Message
 // %n - Tag
+// %N - Short tag
 // %t - Time
 // %P - Process ID
 // %T - Thread ID
@@ -307,6 +308,20 @@ static char _format_prio(LogLevel prio)
     }
 }
 
+static std::string _format_short_tag(std::string_view tag)
+{
+    // Keep first letter in each component
+    auto pieces = split_sv(tag, '/');
+    if (!pieces.empty()) {
+        for (auto it = pieces.begin(); it != pieces.end() - 1; ++it) {
+            if (!it->empty() && isalnum(it->front())) {
+                *it = it->substr(0, 1);
+            }
+        }
+    }
+    return join(pieces, '/');
+}
+
 static std::string _format_rec(const LogRecord &rec)
 {
     std::string buf;
@@ -334,6 +349,10 @@ static std::string _format_rec(const LogRecord &rec)
                 buf += rec.tag;
                 break;
 
+            case 'N':
+                buf += _format_short_tag(rec.tag);
+                break;
+
             case 't':
                 if (!time_buf) {
                     std::tm tm;