## Changes
While investigating #1629, I found that Go doesn't allow characters
outside the set documented at
https://pkg.go.dev/golang.org/x/mod/module#CheckFilePath.
To fix this, I changed the relevant test case to create the fixtures it
needs instead of loading it from the `testdata` directory (in
`renderer_test.go`).
Some test cases in `config_test.go` depended on templated paths without
needing to do so. In the process of fixing this, I refactored these
tests slightly to reduce dependencies between them.
This change also adds a test case to ensure that all files in the
repository are allowed to be part of a module (per the earlier
`CheckFilePath` function).
Fixes#1629.
## Tests
I manually confirmed I could import the repository as a Go module.
Pieter Noordhuis