Modernizes rust script and renames from cargo.sh to rust.sh.

.rc.d/cargo.sh

@@ -1,4 +0,0 @@
-if [ -f "$HOME/.cargo/env" ]; then
-    # For sh/bash/zsh/ash/dash/pdksh
-    source "$HOME/.cargo/env"
-fi

.rc.d/rust.sh

@@ -0,0 +1,75 @@
+# Setup Rust / Cargo environment, tools, and shell completions
+_setup_cargo() {
+    [ -n "$ZSH_VERSION" ] && setopt localoptions nonomatch nullglob
+
+    _add_to_path() {
+        [ -d "$1" ] || return 0
+        case ":$PATH:" in
+            *":$1:"*) ;;
+            *) PATH="$1:$PATH"; export PATH ;;
+        esac
+    }
+
+    # 1. Respect or detect CARGO_HOME and RUSTUP_HOME
+    if [ -z "$CARGO_HOME" ] && [ -d "$HOME/.cargo" ]; then
+        export CARGO_HOME="$HOME/.cargo"
+    fi
+    if [ -z "$RUSTUP_HOME" ] && [ -d "$HOME/.rustup" ]; then
+        export RUSTUP_HOME="$HOME/.rustup"
+    fi
+
+    _cargo_dir="${CARGO_HOME:-$HOME/.cargo}"
+
+    # 2. Source official env file if present, or add bin directory to PATH
+    if [ -f "$_cargo_dir/env" ]; then
+        \. "$_cargo_dir/env"
+    elif [ -d "$_cargo_dir/bin" ]; then
+        _add_to_path "$_cargo_dir/bin"
+    fi
+
+    # 3. Fallback search for system or alternative Cargo/Rust locations if not in PATH
+    if ! command -v cargo >/dev/null 2>&1; then
+        for _cand in \
+            "/usr/local/cargo/bin" \
+            "/opt/homebrew/opt/rust/bin" \
+            "/usr/local/opt/rust/bin" \
+            "/opt/homebrew/bin" \
+            "/usr/local/bin" \
+            "$HOME/.local/bin"
+        do
+            if [ -x "$_cand/cargo" ]; then
+                _add_to_path "$_cand"
+                break
+            fi
+        done
+    fi
+
+    # 4. Enable shell completions if available and files are present
+    if command -v cargo >/dev/null 2>&1; then
+        _rustup_dir="${RUSTUP_HOME:-$HOME/.rustup}"
+
+        if [ -n "$BASH_VERSION" ]; then
+            for _comp in \
+                "$_rustup_dir"/toolchains/*/etc/bash_completion.d/cargo \
+                "$_rustup_dir"/toolchains/*/etc/bash_completion.d/rustup \
+                "/opt/homebrew/etc/bash_completion.d/cargo" \
+                "/usr/share/bash-completion/completions/cargo"
+            do
+                if [ -r "$_comp" ]; then
+                    \. "$_comp"
+                fi
+            done
+        elif [ -n "$ZSH_VERSION" ]; then
+            for _zsh_comp_dir in "$_rustup_dir"/toolchains/*/share/zsh/site-functions; do
+                if [ -d "$_zsh_comp_dir" ]; then
+                    case " ${fpath[*]} " in
+                        *" $_zsh_comp_dir "*) ;;
+                        *) fpath=("$_zsh_comp_dir" "${fpath[@]}") ;;
+                    esac
+                fi
+            done
+        fi
+    fi
+}
+_setup_cargo
+unset -f _setup_cargo _add_to_path