CI: fix minimal-versions resolution (#593)

To avoid nightly regressions breaking the build, the CI configuration
has been updated to *only* use nightly for resolving Cargo.lock by using
`cargo update -Z minimal-versions`.

Previously, it was running `cargo check` which would attempt to compile
all of the dependencies and the code, which is why the diagnostic bug
was triggered. By avoiding any kind of code compilation using nightly we
can avoid such regressions in the future.

Additionally, the clippy job has been changed to run on the latest
stable release (1.73.0) rather than nightly, which will prevent future
clippy lints from breaking the build. Instead, they can be addressed
when clippy is updated.

.github/workflows/curve25519-dalek.yml

@@ -134,10 +134,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v3
-    # First run `cargo +nightly -Z minimal-verisons check` in order to get a
-    # Cargo.lock with the oldest possible deps
+    # Re-resolve Cargo.lock with minimal versions
     - uses: dtolnay/rust-toolchain@nightly
-    - run: cargo -Z minimal-versions check --no-default-features --features serde
+    - run: cargo update -Z minimal-versions
     # Now check that `cargo build` works with respect to the oldest possible
     # deps and the stated MSRV
     - uses: dtolnay/[email protected]

.github/workflows/ed25519-dalek.yml

@@ -24,10 +24,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v3
-      # Now run `cargo +nightly -Z minimal-verisons check` in order to get a
-      # Cargo.lock with the oldest possible deps
+      # Re-resolve Cargo.lock with minimal versions
     - uses: dtolnay/rust-toolchain@nightly
-    - run: cargo -Z minimal-versions check --no-default-features --features serde
+    - run: cargo update -Z minimal-versions
       # Now check that `cargo build` works with respect to the oldest possible
       # deps and the stated MSRV
     - uses: dtolnay/[email protected]

.github/workflows/workspace.yml

@@ -85,7 +85,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v3
-    - uses: dtolnay/rust-toolchain@nightly
+    - uses: dtolnay/rust-toolchain@1.73.0
       with:
         components: clippy
     - run: cargo clippy --target x86_64-unknown-linux-gnu --all-features

.github/workflows/x25519-dalek.yml

@@ -24,10 +24,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v3
-      # Now run `cargo +nightly -Z minimal-verisons check` in order to get a
-      # Cargo.lock with the oldest possible deps
+      # Re-resolve Cargo.lock with minimal versions
     - uses: dtolnay/rust-toolchain@nightly
-    - run: cargo -Z minimal-versions check --no-default-features --features serde
+    - run: cargo update -Z minimal-versions
       # Now check that `cargo build` works with respect to the oldest possible
       # deps and the stated MSRV
     - uses: dtolnay/[email protected]