Set nextest behavior on empty runs more explicitly

`cargo nextest` will eventually default to `--no-tests=error`, but
it doesn't yet. Currently, `cargo nextest run -p gitoxide-core`
runs no tests, as there are non in `gitoxide-core` (checked by
running `git grep '#.*\[.*test' -- gitoxide-core`).

This adds `--no-tests=warn` to that command in the `unit-tests`
recipe in `justfile`, to make the default behavior explicit.

For CI (but not otherwise), this sets the default to `fail` now by
setting the `NEXTEST_NO_TESTS` environment variable. (This is
overridden by `--no-tests=warn` so it does not fail `unit-tests`.)

Author: EliahKagan

.github/workflows/ci.yml

@@ -19,6 +19,7 @@ permissions:
 env:
   CARGO_TERM_COLOR: always
   CLICOLOR: '1'
+  NEXTEST_NO_TESTS: fail
 
 jobs:
   pure-rust-build:

justfile

@@ -191,7 +191,7 @@ unit-tests:
     cargo nextest run -p gix --no-default-features --features basic,extras,comfort,need-more-recent-msrv
     cargo nextest run -p gix --features async-network-client
     cargo nextest run -p gix --features blocking-network-client
-    cargo nextest run -p gitoxide-core --lib
+    cargo nextest run -p gitoxide-core --lib --no-tests=warn
 
 # These tests aren't run by default as they are flaky (even locally)
 unit-tests-flaky: