Remove once_cell dependency

Remove the once_cell dependency now that similar functionality is
provided by the standard library.

Cargo.toml

@@ -48,7 +48,6 @@ grev = "0.1.3"
 anyhow = "1.0.68"
 clap = {version = "4.1.4", features = ["derive"]}
 clap_complete = {version = "4.1.1", optional = true}
-once_cell = "1.17.0"
 regex = {version = "1.7.1", default-features = false, features = ["std"]}
 tempfile = {version = "3.3.0", optional = true}
 time = {version = "0.3.18", features = ["formatting", "local-offset", "parsing"]}

src/btrfs/btrfs.rs

@@ -13,12 +13,11 @@ use std::path::PathBuf;
 use std::str::FromStr as _;
 use std::sync::atomic::AtomicBool;
 use std::sync::atomic::Ordering;
+use std::sync::LazyLock;
 
 use anyhow::Context as _;
 use anyhow::Result;
 
-use once_cell::sync::Lazy;
-
 use regex::Regex;
 
 use crate::ops::FileOps;
@@ -40,7 +39,7 @@ const PATH_STRING: &str = r".+";
 /// by the snapshots() method. Each line is expected to be following the
 /// pattern:
 /// ID A gen B top level C path PATH
-static SNAPSHOTS_LINE_REGEX: Lazy<Regex> = Lazy::new(|| {
+static SNAPSHOTS_LINE_REGEX: LazyLock<Regex> = LazyLock::new(|| {
   Regex::new(&format!(
       r"^ID {NUMS_STRING} gen (?P<gen>{NUMS_STRING}) top level {NUMS_STRING} path (?P<path>{PATH_STRING})$"
   )).expect("failed to create snapshot regular expression")

src/snapshot.rs

@@ -1,4 +1,4 @@
-// Copyright (C) 2023 Daniel Mueller <deso@posteo.net>
+// Copyright (C) 2023-2024 Daniel Mueller <deso@posteo.net>
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 use std::borrow::Cow;
@@ -10,13 +10,12 @@ use std::fmt::Result as FmtResult;
 use std::path::Path;
 use std::path::MAIN_SEPARATOR;
 use std::str::FromStr as _;
+use std::sync::LazyLock;
 
 use anyhow::ensure;
 use anyhow::Context as _;
 use anyhow::Result;
 
-use once_cell::sync::Lazy;
-
 use time::format_description::modifier::Day;
 use time::format_description::modifier::Hour;
 use time::format_description::modifier::Minute;
@@ -52,7 +51,7 @@ const ENCODED_INTRA_COMPONENT_SEPARATOR: &str = "-";
 const ENCODED_COMPONENT_SEPARATOR: &str = "_";
 
 /// The UTC time zone offset we use throughout the program.
-static UTC_OFFSET: Lazy<UtcOffset> = Lazy::new(|| {
+static UTC_OFFSET: LazyLock<UtcOffset> = LazyLock::new(|| {
   if cfg!(test) || cfg!(feature = "test") {
     // SAFETY: Our tests do not mutate the environment.
     let () = unsafe { set_soundness(Soundness::Unsound) };