## Changes
- Enable new linter: testifylint.
- Apply fixes with --fix.
- Fix remaining issues (mostly with aider).
There were 2 cases we --fix did the wrong thing - this seems to a be a
bug in linter: https://github.com/Antonboom/testifylint/issues/210
Nonetheless, I kept that check enabled, it seems useful, just need to be
fixed manually after autofix.
## Tests
Existing tests
## Changes
Enable gofumpt and goimports in golangci-lint and apply autofix.
This makes 'make fmt' redundant, will be cleaned up in follow up diff.
## Tests
Existing tests.
## Changes
Remove two duplicate implementations of the same logic, switch
everywhere to folders.FindDirWithLeaf.
Add Abs() call to FindDirWithLeaf, it cannot really work on relative
paths.
## Tests
Existing tests.