Follow-up to #630.
The check for the target git sha can does not work in the molecule step.
Instead expose the sha through an env variable in GitHub actions.
file.write() does not guarantee that a file handle contains anything
without calling an accompanying file.flush()
For typical files that are larger than the OS-file buffer, this is no
problem
For small files (e.g. 64 characters in a .TXT), this race condition
leads to `inode/x-empty` because the file inode is created, but no
content is written to it
"Upgrade" path includes multiple paths anyway:
- installing the latest official release package
- builing the current PR from source
- upgrading between the two versions
Provide a separate scenario to install the last release, then update to
the current one.
Also includes improved deployment verification (check if uploading a
.txt through the API works).
