cargo update (#112)

Closes #115

Author: github-actions[bot]

.github/workflows/rust.yml

@@ -23,16 +23,16 @@ jobs:
         rust:
           - stable
           - 1.46.0 # lib MSRV
-          - 1.60.0 # cli MSRV
+          - 1.64.0 # cli MSRV
         include:
           - os: ubuntu-latest
             rust: stable
             lint: 1
           - rust: stable
             rust-args: --all-features
           - rust: 1.46.0
-            no-lock: 1
-          - rust: 1.60.0
+            old-cargo-compat: 1
+          - rust: 1.64.0
             rust-args: --all-features
         exclude:
           # rust < 1.54 does not work on macos >= 12:
@@ -42,7 +42,7 @@ jobs:
           - os: macos-11
             rust: stable
           - os: macos-11
-            rust: 1.60.0
+            rust: 1.64.0
     runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout source
@@ -56,14 +56,20 @@ jobs:
 
       - uses: Swatinem/rust-cache@v1
 
-      # If we're testing with Rust < 1.60, cargo won't be able to find
-      # the clap version specified in Cargo.lock, so remove the lockfile.
-      # This is safe because applications that only use us as a library will
-      # also ignore our Cargo.lock.
-      # https://users.rust-lang.org/t/optional-dependencies-and-msrv/82151
-      - name: Prune Cargo.lock
-        if: matrix.no-lock
-        run: rm Cargo.lock
+      - name: Compatibility fixes for older versions of cargo
+        if: matrix.old-cargo-compat
+        run: |
+          # If we're testing with Rust < 1.60, cargo won't be able to find
+          # the clap version specified in Cargo.lock, so remove the lockfile.
+          # This is safe because applications that only use us as a library
+          # will also ignore our Cargo.lock.
+          # https://users.rust-lang.org/t/optional-dependencies-and-msrv/82151
+          cargo update -p clap --precise 3.2.25
+          # Downgrade the following crates because they require edition 2021
+          cargo update -p serde --precise 1.0.156
+          cargo update -p thiserror --precise 1.0.39
+          cargo update -p quote --precise 1.0.30
+          cargo update -p proc-macro2 --precise 1.0.65
 
       - name: cargo test
         uses: actions-rs/cargo@v1