Detached head causes build failure

[prstedman]

Hi,

I am trying to build an image for the SFT1200 router. I followed the install steps but when I get to the checkout step -

git checkout v3.216_ar150/ar300m/ar750/ar750s/b1300/b2200/e750/mifi/mt1300/mt300n-v2/mv1000-emmc/n300/s1300/sf1200/sft1200/usb150/x300b/x750/xe300

I get a 'detached HEAD' warning. When I then build using a dockerfile, I get the following error -

hint: Pulling without specifying how to reconcile divergent branches is
hint: discouraged. You can squelch this message by running one of the following
hint: commands sometime before your next pull:
hint: 
hint:   git config pull.rebase false  # merge (the default strategy)
hint:   git config pull.rebase true   # rebase
hint:   git config pull.ff only       # fast-forward only
hint: 
hint: You can replace "git config" with "git config --global" to set a default
hint: preference for all repositories. You can also pass --rebase, --no-rebase,
hint: or --ff-only on the command line to override the configured default per
hint: invocation.
You are not currently on a branch.
Please specify which branch you want to merge with.
See git-pull(1) for details.

    git pull <remote> <branch>

Traceback (most recent call last):
  File "gl_image", line 606, in <module>
    sys.exit(main(sys.argv))
  File "gl_image", line 354, in main
Update glinet repository ......
    check_call("git pull", shell=True, cwd=dir_name)
  File "/usr/lib/python2.7/subprocess.py", line 190, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command 'git pull' returned non-zero exit status 1

If I skip the checkout step or undo it with git switch - then it builds the image, but that bricks the router.

Could someone tell me where I'm going wrong?

Thank you!