Adds the commit to the output folder

I thought it will be a good idea to write the commit into the output
folder to better track the code version responsible for the results.

src/modules/solver/moduleSolver.f90

@@ -518,6 +518,11 @@ MODULE moduleSolver
 
       INTEGER, INTENT(in):: t
 
+      IF (t == tInitial) THEN
+        CALL SYSTEM('git rev-parse HEAD > ' // path // folder // '/' // 'fpack_commit.txt')
+
+      END IF
+
       counterOutput = counterOutput + 1
       IF (counterOutput >= triggerOutput .OR. &
           t == tFinal .OR. t == tInitial) THEN