Add toolchain management script

scripts/switch_rust_toolchain.sh

@@ -0,0 +1,82 @@
+#!/bin/sh
+
+set -eu
+
+RUST_TOOLCHAIN=
+
+SCRIPTS_DIR=$(dirname "$0")
+BASENAME=$(basename "$0")
+WORKSPACE_DIR=$(cd $SCRIPTS_DIR/.. && pwd)
+RUST_TOOLCHAIN_FILE="$WORKSPACE_DIR/rust-toolchain"
+
+MSRV=$(cat "$WORKSPACE_DIR/truc/Cargo.toml" | sed -n -e 's/^\s*rust-version\s*=\s*"\([^"]*\)"\s*$/\1/p')
+
+usage() {
+    echo "$BASENAME -c|--clear"
+    echo "    clear \`rust-toolchain\` (use system default)"
+    echo "$BASENAME -m|--msrv"
+    echo "    select \"$MSRV\""
+    echo "$BASENAME -s|--stable"
+    echo "    select \"stable\""
+    echo "$BASENAME -n|--nightly"
+    echo "    select \"nightly\""
+    echo "$BASENAME -v|--version <version>"
+    echo "    select specific version"
+    echo "$BASENAME -h|--help"
+    echo "    show this help and exit"
+}
+
+while [ $# -gt 0 ]; do
+    case $1 in
+        -c|--clear)
+            RUST_TOOLCHAIN=
+            shift
+            ;;
+        -m|--msrv)
+            RUST_TOOLCHAIN="$MSRV"
+            shift
+            ;;
+        -s|--stable)
+            RUST_TOOLCHAIN="stable"
+            shift
+            ;;
+        -n|--nightly)
+            RUST_TOOLCHAIN="nightly"
+            shift
+            ;;
+        -v|--version)
+            RUST_TOOLCHAIN="$2"
+            shift
+            shift
+            ;;
+        -h|--help)
+            usage
+            exit 0
+            shift
+            ;;
+        -*|--*)
+            echo "Unknown option $1" > /dev/stderr
+            echo > /dev/stderr
+            usage > /dev/stderr
+            exit 1
+            ;;
+        *)
+            echo "Unexpected positional argument" > /dev/stderr
+            echo > /dev/stderr
+            usage > /dev/stderr
+            exit 1
+            ;;
+    esac
+done
+
+echo "Removing \`Cargo.lock\`..."
+rm -f "$WORKSPACE_DIR/Cargo.lock"
+
+if [ x"$RUST_TOOLCHAIN" = x ]
+then
+    echo "Clearing \`$RUST_TOOLCHAIN_FILE\`..."
+    rm -f "$RUST_TOOLCHAIN_FILE"
+else
+    echo "Switching $RUST_TOOLCHAIN_FILE to \"$RUST_TOOLCHAIN\""
+    echo "$RUST_TOOLCHAIN" >| "$RUST_TOOLCHAIN_FILE"
+fi