Can't get sshfs mount in fstab to work

[Colin Law]

After much googling and experimenting I have run out of ideas on this
one.  In /etc/fstab I have

sshfs#user_name at 192.168.1.96:/media/usb/gitrepos /media/gitrepos fuse
uid=1000,gid=1000,idmap=user,IdentityFile=/home/user_name/.ssh/id_rsa,allow_other
0 0

If I do
sudo mount /media/gitrepos
the directory is mounted as expected.  It does not ask for password as
I have setup the ssh keys.  When I boot however it stops during the
boot saying that the mount has failed and giving me the option of
dropping into a shell to fix it, or Skipping the mount.  Skipping
allows the boot to continue, but the share is not mounted of course.
I cannot find any log messages anywhere to give me a clue as to the
cause of the problem.

Any suggestions will be much appreciated.

Colin