Failure to retrieve software version from git checkout

Dear experts,

I get an error which is apparently related to the following function

https://gitlab.cern.ch/silab/bdaq53/blob/v0.9.0/bdaq53/scan_base.py#L34

The error message is

[rd53a@marrd53a scans]$ python scan_digital.py

2018-12-13 17:08:52,579 - [DigitalScan    ] - WARNING You are using the default chip configuration file. Please use a chip specific configuration file!

2018-12-13 17:08:52,579 - [DigitalScan    ] - INFO    Initializing DigitalScan...

2018-12-13 17:08:52,726 - [Periphery      ] - INFO    Periphery is disabled.

2018-12-13 17:08:52,731 - [RD53A          ] - SUCCESS Found board USBPix3 with SMA running firmware version 0.9

2018-12-13 17:08:52,731 - [RD53A          ] - INFO    Si570 oscillator is already configured

2018-12-13 17:08:52,732 - [RD53A          ] - INFO    Initializing communication with chip...

2018-12-13 17:08:52,841 - [RD53A          ] - INFO    Aurora receiver running at 1.28Gb/s

2018-12-13 17:08:52,842 - [RD53A          ] - INFO    1 Aurora lane active

2018-12-13 17:08:52,882 - [RD53A          ] - SUCCESS Communication established

2018-12-13 17:08:53,554 - [DigitalScan    ] - INFO    Configuring chip...

Traceback (most recent call last):

  File "scan_digital.py", line 80, in <module>

    scan.start(**local_configuration)

  File "/home/rd53a/RD53_DAQ/bdaq53_new_v0.9.0/bdaq53/bdaq53/scan_base.py", line 641, in start

    self._configure_readout(**kwargs)  # Raw data handling

  File "/home/rd53a/RD53_DAQ/bdaq53_new_v0.9.0/bdaq53/bdaq53/scan_base.py", line 538, in _configure_readout

    self.dump_configuration(**kwargs)

  File "/home/rd53a/RD53_DAQ/bdaq53_new_v0.9.0/bdaq53/bdaq53/scan_base.py", line 405, in dump_configuration

    row['value'] = get_software_version()

  File "/home/rd53a/RD53_DAQ/bdaq53_new_v0.9.0/bdaq53/bdaq53/scan_base.py", line 43, in get_software_version

    active_branch = repo.active_branch

  File "/home/rd53a/anaconda2/lib/python2.7/site-packages/GitPython-2.1.11-py2.7.egg/git/repo/base.py", line 696, in active_branch

    return self.head.reference

  File "/home/rd53a/anaconda2/lib/python2.7/site-packages/GitPython-2.1.11-py2.7.egg/git/refs/symbolic.py", line 275, in _get_reference

    raise TypeError("%s is a detached symbolic reference as it points to %r" % (self, sha))

TypeError: HEAD is a detached symbolic reference as it points to 'bb0f659a993b72927ec631b4eedbbc76c8139112'

Closing remaining open files:/home/rd53a/RD53_DAQ/bdaq53_new_v0.9.0/bdaq53/bdaq53/scans/output_data/20181213_170852_digital_scan.h5...done

The way I set up the code is through

git clone https://gitlab.cern.ch/silab/bdaq53.git

git checkout tags/v0.9.0

As it is a tag, this looks consistent with the returned HEAD as active git branch.

Is there another recommended way to set up a given tag to avoid this issue?

Thank you very much for your feedback

Best regards,

Thomas