message: Align AppVeyor to use 1.28 for minimal versions
  .. like Travis CI's setup.
diff: @@ -13,7 +13,7 @@ install:
  - appveyor-retry appveyor DownloadFile https://win.rustup.rs/ -FileName rustup-init.exe
  - rustup-init.exe -y --default-host x86_64-pc-windows-msvc --default-toolchain nightly
  - set PATH=%PATH%;C:\Users\appveyor\.cargo\bin
  - - if defined MINIMAL_VERSIONS rustup toolchain install stable
  + - if defined MINIMAL_VERSIONS rustup toolchain install 1.28.0
  - rustup target add %OTHER_TARGET%
  - rustc -V
  - cargo -V
  @@ -27,5 +27,5 @@ test_script:
  # we don't have ci time to run the full `cargo test` with `minimal-versions` like
  # - if defined MINIMAL_VERSIONS cargo +nightly generate-lockfile -Z minimal-versions && cargo +stable test
  # so we just run `cargo check --tests` like
  - - if defined MINIMAL_VERSIONS cargo +nightly generate-lockfile -Z minimal-versions && cargo +stable check --tests
  + - if defined MINIMAL_VERSIONS cargo +nightly generate-lockfile -Z minimal-versions && cargo check --tests
  - if NOT defined MINIMAL_VERSIONS cargo test
  