[API] Job model validates that the script exists in the repository at script_version
This should be an inexpensive check, and it could help shorten the debug cycle for common job setup problems. e.g., script not under
crunch_scripts/, wrong branch specified in script_version, etc.
On job creation or relevant update, validate:
- The specified script exists
- It has the executable bit set
When the API server is checking the repository, use
git ls-tree to verify that the script exists and is executable at the specified script_version.
Verify that this works on Git 1.7.10. If it doesn't, figure out when the necessary Git functionality was added, and document that version requirement.