Ensure that MSRV tests do not regress

When testing with older versions of rustc, there's a CI failure mode
when our dependency, which used to be compatible with that Rust version,
publishes a new version which can't be compiled using that old Rust
anymore. That's pretty unfortunate, as that means that third parties can
break our CI without any changes to the code in this repo.

To protect against that, let's use Cargo.lock on CI, but only when
testing against older versions. For stable Rust, we continue to generate
Cargo.lock with freshest dependencies. Implementation wise, we save
known-good Cargo.lock as `Cargo.lock.msrv`, and just copy that in every
relevant CI job.

To get a working `Cargo.lock.msrv`, I run `cargo +nightly
generate-lockfile -Zminimal-versions` -- that is guaranteed to support
the oldest Rust version we can.

1 files changed, 318 insertions, 0 deletions

diff --git a/Cargo.lock.msrv b/Cargo.lock.msrv
new file mode 100644
index 00000000..d7936db8
--- /dev/null
+++ b/Cargo.lock.msrv
@@ -0,0 +1,318 @@
+# This file was generated by running the following command:
+#     `cargo +nightly generate-lockfile -Zminimal-versions`
+# We use it on CI to test non-latest-stable Rust versions.
+version = 3
+
+[[package]]
+name = "assert-impl"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "40e79d69c321c1d98eb55e4890ed07e885c071b9575960a9e742d2931581f496"
+
+[[package]]
+name = "autocfg"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f8aac770f1885fd7e387acedd76065302551364496e46b3dd00860b2f8359b9d"
+
+[[package]]
+name = "bitflags"
+version = "1.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2da1976d75adbe5fbc88130ecd119529cf1cc6a93ae1546d8696ee66f0d21af1"
+
+[[package]]
+name = "byteorder"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c40977b0ee6b9885c9013cd41d9feffdd22deb3bb4dc3a71d901cc7a77de18c8"
+
+[[package]]
+name = "caps"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d092fbb6657fb1f98a7da70c14335ac97e5a9477e1a8156d4bbf19a3a7aece51"
+dependencies = [
+ "errno",
+ "libc",
+ "thiserror",
+]
+
+[[package]]
+name = "cc"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7db2f146208d7e0fbee761b09cd65a7f51ccc38705d4e7262dad4d73b12a76b1"
+
+[[package]]
+name = "cfg-if"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d4c819a1287eb618df47cc647173c5c4c66ba19d888a6e50d605672aed3140de"
+
+[[package]]
+name = "cfg-if"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
+
+[[package]]
+name = "errno"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b2c858c42ac0b88532f48fca88b0ed947cad4f1f64d904bcd6c9f138f7b95d70"
+dependencies = [
+ "kernel32-sys",
+ "libc",
+ "winapi 0.2.4",
+]
+
+[[package]]
+name = "getrandom"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ee8025cf36f917e6a52cce185b7c7177689b838b7ec138364e50cc2277a56cf4"
+dependencies = [
+ "cfg-if 0.1.2",
+ "libc",
+ "wasi",
+]
+
+[[package]]
+name = "kernel32-sys"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ad1ca084b49bfd975182288e1a5f1d27ea34ff2d6ae084ae5e66e1652427eada"
+dependencies = [
+ "winapi 0.2.4",
+ "winapi-build",
+]
+
+[[package]]
+name = "lazy_static"
+version = "1.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a374c89b9db55895453a74c1e38861d9deec0b01b405a82516e9d5de4820dea1"
+
+[[package]]
+name = "libc"
+version = "0.2.102"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a2a5ac8f984bfcf3a823267e5fde638acc3325f6496633a5da6bb6eb2171e103"
+
+[[package]]
+name = "memoffset"
+version = "0.6.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f83fb6581e8ed1f85fd45c116db8405483899489e38406156c25eb743554361d"
+dependencies = [
+ "autocfg",
+]
+
+[[package]]
+name = "nix"
+version = "0.23.0"
+dependencies = [
+ "assert-impl",
+ "bitflags",
+ "caps",
+ "cc",
+ "cfg-if 1.0.0",
+ "lazy_static",
+ "libc",
+ "memoffset",
+ "rand",
+ "semver",
+ "sysctl",
+ "tempfile",
+]
+
+[[package]]
+name = "ppv-lite86"
+version = "0.2.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "237a5ed80e274dbc66f86bd59c1e25edc039660be53194b5fe0a482e0f2612ea"
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "19f287c234c9b2d0308d692dee5c449c1a171167a6f8150f7cf2a49d8fd96967"
+dependencies = [
+ "unicode-xid",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7ab938ebe6f1c82426b5fb82eaf10c3e3028c53deaa3fbe38f5904b37cf4d767"
+dependencies = [
+ "proc-macro2",
+]
+
+[[package]]
+name = "rand"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a76330fb486679b4ace3670f117bbc9e16204005c4bde9c4bd372f45bed34f12"
+dependencies = [
+ "libc",
+ "rand_chacha",
+ "rand_core",
+ "rand_hc",
+]
+
+[[package]]
+name = "rand_chacha"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e12735cf05c9e10bf21534da50a147b924d555dc7a547c42e6bb2d5b6017ae0d"
+dependencies = [
+ "ppv-lite86",
+ "rand_core",
+]
+
+[[package]]
+name = "rand_core"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "34cf66eb183df1c5876e2dcf6b13d57340741e8dc255b48e40a26de954d06ae7"
+dependencies = [
+ "getrandom",
+]
+
+[[package]]
+name = "rand_hc"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3190ef7066a446f2e7f42e239d161e905420ccab01eb967c9eb27d21b2322a73"
+dependencies = [
+ "rand_core",
+]
+
+[[package]]
+name = "redox_syscall"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bac5c4ce99d34f37ce30e45606946fcd6331223f1c98af4d29c5b6c4977d675b"
+dependencies = [
+ "bitflags",
+]
+
+[[package]]
+name = "remove_dir_all"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dfc5b3ce5d5ea144bb04ebd093a9e14e9765bcfec866aecda9b6dec43b3d1e24"
+dependencies = [
+ "winapi 0.3.0",
+]
+
+[[package]]
+name = "semver"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "76b5842e81eb9bbea19276a9dbbda22ac042532f390a67ab08b895617978abf3"
+
+[[package]]
+name = "syn"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9f8c8eab7d9f493cd89d4068085651d81ac7d39c56eb64f7158ea514b156e280"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-xid",
+]
+
+[[package]]
+name = "sysctl"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3c7da87d95ab91294ebf2132bf36e1c4f6ac1df11db4c63105858cb175e2141c"
+dependencies = [
+ "byteorder",
+ "errno",
+ "libc",
+]
+
+[[package]]
+name = "tempfile"
+version = "3.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dac1c663cfc93810f88aed9b8941d48cabf856a1b111c29a40439018d870eb22"
+dependencies = [
+ "cfg-if 1.0.0",
+ "libc",
+ "rand",
+ "redox_syscall",
+ "remove_dir_all",
+ "winapi 0.3.0",
+]
+
+[[package]]
+name = "thiserror"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d032db01164196ffdea5d016aa5cacd9d163a4fb00b85e9fc3ad18c5b1a3951d"
+dependencies = [
+ "thiserror-impl",
+]
+
+[[package]]
+name = "thiserror-impl"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e9d53f5a0d2bd66d1d841e69a4beb74a226216b3f158ff0c534578f76e7beac9"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "unicode-xid"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "826e7639553986605ec5979c7dd957c7895e93eabed50ab2ffa7f6128a75097c"
+
+[[package]]
+name = "wasi"
+version = "0.9.0+wasi-snapshot-preview1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cccddf32554fecc6acb585f82a32a72e28b48f8c4c1883ddfeeeaa96f7d8e519"
+
+[[package]]
+name = "winapi"
+version = "0.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5350e40d908c7e8b9e5c9edb541ca47cc617c6229d3575a46da6f550f36c96fd"
+
+[[package]]
+name = "winapi"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b3ad91d846a4a5342c1fb7008d26124ee6cf94a3953751618577295373b32117"
+dependencies = [
+ "winapi-i686-pc-windows-gnu",
+ "winapi-x86_64-pc-windows-gnu",
+]
+
+[[package]]
+name = "winapi-build"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2d315eee3b34aca4797b2da6b13ed88266e6d612562a0c46390af8299fc699bc"
+
+[[package]]
+name = "winapi-i686-pc-windows-gnu"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a16a8e2ebfc883e2b1771c6482b1fb3c6831eab289ba391619a2d93a7356220f"
+
+[[package]]
+name = "winapi-x86_64-pc-windows-gnu"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8ca29cb03c8ceaf20f8224a18a530938305e9872b1478ea24ff44b4f503a1d1d"