Truncate status log after 100 lines

The Git history is sufficient for viewing past status messages.
Additionally, long status log files tend to take long to render. With
this commit, only the most recent 100 lines are kept, and this number
can be configured.

benchmark.py

@@ -151,12 +151,13 @@ def writeStatus(message, config):
 
 	if os.path.exists(statusFilename):
 		with open(statusFilename, "r") as statusFile:
-			content = statusFile.read()
+			# add the previous status messages, but trancate them
+			content = statusFile.readlines()[0:(config["storage"]["statusLogSize"] - 1)]
 	else:
 		content = ""
 
 	with open(statusFilename, "w") as statusFile:
-		print(time.strftime("%Y-%m-%d %H:%M:%S %z") + "\t" + message + "\n" + content, file = statusFile, end = "")
+		print(time.strftime("%Y-%m-%d %H:%M:%S %z") + "\t" + message + "\n" + "".join(content), file = statusFile, end = "")
 
 	git(["add", "status.log"], dataDir)
 	git(["commit", "-m Update status: " + message], dataDir)

config.example.yaml

@@ -14,6 +14,8 @@ storage:
     results: results
     config: config
     status: status
+  # the maximum size of the status log in lines
+  statusLogSize: 100
 
 executables:
   timeout: