pack install git ref error in st2packs docker build

SUMMARY

Using the st2 pack install from st2common/util/pack_management.py in the st2packs docker builder, an error condition on getting branch name can occur.

ISSUE TYPE

Pick one below and delete the rest:

• Bug Report

STACKSTORM VERSION

st2packs base
https://github.com/StackStorm/st2packs-dockerfiles

OS / ENVIRONMENT / INSTALL METHOD

Docker - st2packs docker builder
https://github.com/StackStorm/st2packs-dockerfiles

STEPS TO REPRODUCE

To reproduce, we use a CI job to build packs for changes on master, tags, and certain branches, e.g. release.

The CI will checkout the release branch, and then the Docker file will run copying the pack files into the container and attempting to install:

FROM myregistry/st2/base:v1.0.0 AS builder

COPY . /opt/stackstorm/packs/my-pack

RUN /opt/stackstorm/st2/bin/st2-pack-install /opt/stackstorm/packs/my-pack

Now we did realize now that we should be using st2-pack-install with a file prefix, e.g. st2-pack-install file:///opt/my-pack

However, the above Dockerfile process has worked for master and tags, just not this release branch

EXPECTED RESULTS

pack to install with git ref of a branch or for this to error out on all git ref's

ACTUAL RESULTS

errors

 File "/opt/stackstorm/st2/lib/python2.7/site-packages/st2common/util/pack_management.py", line 119, in download_pack
    ref=pack_version)
  File "/opt/stackstorm/st2/lib/python2.7/site-packages/st2common/util/pack_management.py", line 163, in clone_repo
    raise e
TypeError: HEAD is a detached symbolic reference as it points to 'dd4047d9816aa31f5d65df56b1cd420c2dff3add'
The command '/bin/sh -c /opt/stackstorm/st2/bin/st2-pack-install /opt/stackstorm/packs/foo' returned a non-zero code: 1

Start in st2common/util/pack_management.py, especially download_pack and clone_repo, and reproduce the failure with the st2-pack-install command shown in the Docker build. Trace how the checked-out release branch and pack_version are handled when HEAD is detached. Done means the documented branch-ref case installs successfully, or the command reports the same clear error for unsupported refs.