Enable SdFat's sateTime callback for timestamping

SdFat requries the dateTimeCallback call (global for everything) to update dates and times on created files. Because the callback signature doesn't have space for us to provide any parameters, we cannot get the the File, Dir, or FS object's dateTimeCB member. Instead, just go with `time(null)` as the callback function which is right in all but the most esoteric cases.
esp8266 · earlephilhower · Feb 22, 2020 · Jan 7, 2020 · Jan 11, 2020 · Jan 11, 2020
commit 76a0a1d24cecd232c823dd949dbe7968b2dadcb9
diff --git a/libraries/SDFS/src/SDFS.h b/libraries/SDFS/src/SDFS.h
@@ -156,6 +156,7 @@ class SDFSImpl : public FSImpl
             format();
             _mounted = _fs.begin(_cfg._csPin, _cfg._spiSettings);
         }
+	sdfat::SdFile::dateTimeCallback(dateTimeCB);
         return _mounted;
     }
 
@@ -204,6 +205,17 @@ class SDFSImpl : public FSImpl
         return mktime(&tiempo);
     }
 
+    // Because SdFat has a single, global setting for this we can only use a
+    // static member of our class to return the time/date.  However, since
+    // this is static, we can't see the time callback variable.  Punt for now,
+    // using time(NULL) as the best we can do.
+    static void dateTimeCB(uint16_t *dosYear, uint16_t *dosTime) {
+        time_t now = time(nullptr);
+        struct tm *tiempo = localtime(&now);
+        *dosYear = ((tiempo->tm_year - 1980) << 9) | (tiempo->tm_mon << 5) | tiempo->tm_mday;
+        *dosTime = (tiempo->tm_hour << 11) | (tiempo->tm_min << 5) | tiempo->tm_sec;
+    }
+
 protected:
     friend class SDFileImpl;
     friend class SDFSDirImpl;