prerelease workflow broken

[abathur]

The "Generate Installer Script" workflow hasn't actually updating the prerelease for a while now.

DetSys have asked if we can pretty-please get it updated, because devenv's installation docs conditionally suggest using the prerelease, and the current prerelease was updated before we'd replaced all of the detsys repo URLs in our source--so people are opening issues against the DetSys repo for issues they've already fixed and they have no way to turn off the spigot.

We've fixed two issues with this already:

1. We accidentally clobbered the corresponding hydraJob attr during conflict resolution in May. We've put it back and hydra has built it, now.
2. Fixed a bug in assemble_installer.py that was keeping it from falling into the update branch. (It was checking finished == "1" instead of 1? Not sure if hydra changed here or how this worked before.)

These fixes, however, expose a more intrinsic problem with Nth updates:

• The workflow pulls the binary files in on a branch that doesn't have them tracked.
• The git-auto-commit action tries to check out the prerelease branch and fails because these untracked files would be overwritten by the copies committed there.

The workflow will need to be duplicated or re-enabled for testing; I disabled it since it is now erroring and spamming me with hourly notifications :)

[abathur]

I did take a quick look at the README/issues for git-auto-commit. I didn't see a lever that telegraphed that it was for working around something like this, though they do have several options for appending arbitrary git flags. (But I don't think there's a flag that'll let us keep the untracked files during a branch checkout?)