populate: build with Rust 1.71, as in nixpkgs 23.11

The program needs Rust 1.71, the oldest version its dependencies support,
which Cargo.toml states, so clippy points out what newer versions add.
The lock file is of version 3, which Cargo reads from version 1.53 on.

3 files changed, 4 insertions, 3 deletions

diff --git a/pkgs/populate/Cargo.lock b/pkgs/populate/Cargo.lock
index ea97ade..7c7e150 100644
--- a/pkgs/populate/Cargo.lock
+++ b/pkgs/populate/Cargo.lock
@@ -1,6 +1,6 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
-version = 4
+version = 3
 
 [[package]]
 name = "itoa"
diff --git a/pkgs/populate/Cargo.toml b/pkgs/populate/Cargo.toml
index 4a4face..6bed691 100644
--- a/pkgs/populate/Cargo.toml
+++ b/pkgs/populate/Cargo.toml
@@ -2,6 +2,8 @@
 name = "populate"
 version = "2.0.0-dev"
 edition = "2021"
+# The oldest version the dependencies support, as nixpkgs 23.11 has it.
+rust-version = "1.71"
 description = "Delivers sources to a target directory, as krops' populate"
 license = "WTFPL"
 publish = false
diff --git a/pkgs/populate/src/flake.rs b/pkgs/populate/src/flake.rs
index b6b0790..26373d4 100644
--- a/pkgs/populate/src/flake.rs
+++ b/pkgs/populate/src/flake.rs
@@ -497,8 +497,7 @@ impl<'a> Flakes<'a> {
         let fields = self.fields(sh::draw::DERIVED_STATE, false, &state_args)?;
         let malformed =
             || Failure::Message(format!("error: can't read the state of source {name}"));
-        let (head, rest) = fields.split_at_checked(4).ok_or_else(malformed)?;
-        let [original, key_file, result, target_kind] = head else {
+        let [original, key_file, result, target_kind, rest @ ..] = fields.as_slice() else {
             return Err(malformed());
         };
         let separator = rest