Without the change the eval fails as:
$ nix build --no-link -f. githooks.tests
error:
… while evaluating the 'name' attribute of a derivation
… while evaluating a branch condition
at lib/strings.nix:1194:3:
1193| # First detect the common case of already valid strings, to speed those up
1194| if stringLength string <= 207 && okRegex string != null
| ^
1195| then unsafeDiscardStringContext string
… in the left operand of the AND (&&) operator
at lib/strings.nix:1194:33:
1193| # First detect the common case of already valid strings, to speed those up
1194| if stringLength string <= 207 && okRegex string != null
| ^
1195| then unsafeDiscardStringContext string
(stack trace truncated; use '--show-trace' to show the full, detailed trace)
error: expected a set but found a string: "githooks-cli"
44744fc83f