can't sync .accesslog file

[zhoucheng361]

What happened:
can't sync .accesslog file because it is always appended with logs

What you expected to happen:
should let user know he is sync an infinity file so he can exclude it

How to reproduce it (as minimally and precisely as possible):

Anything else we need to know?

Environment:

• JuiceFS version (use juicefs --version) or Hadoop Java SDK version:
• Cloud provider or hardware configuration running JuiceFS:
• OS (e.g cat /etc/os-release):
• Kernel (e.g. uname -a):
• Object storage (cloud provider and region, or self maintained):
• Metadata engine info (version, cloud provider managed or self maintained):
• Network connectivity (JuiceFS to metadata engine, JuiceFS to object storage):
• Others:

[davies]

.accesslog is a special file, it's OK to fail (rsync may also fail).

We should exclude it when coping a whole file system.