bash: Write bootstrap.sh in POSIX sh to work with Alpine

Signed-off-by: Nathan Chancellor <[email protected]>

Author: nathanchance

.shellcheckrc

@@ -1,4 +1,3 @@
 disable=SC1090
 disable=SC2030
 disable=SC2031
-shell=bash

bash/bootstrap.sh

@@ -1,9 +1,43 @@
-#!/usr/bin/env bash
+#!/bin/sh
 
-set -euxo pipefail
+set -eux
 
 tmp_dir=$(mktemp -d)
 
-curl -LSs https://github.com/nathanchance/env/tarball/main | tar -C "$tmp_dir" -xvzf - --strip-components=1
+is_available() {
+    command -v "$1" >/dev/null 2>&1
+}
 
-"$tmp_dir"/python/root/"$(grep ^ID= /usr/lib/os-release | cut -d= -f2 | sed 's/"//g')".py "$@"
+if is_available curl; then
+    dwnld_cmd="curl -LSs"
+elif is_available wget; then
+    dwnld_cmd="wget -q -O-"
+else
+    echo "[-] No suitable download command could be found!" >&2
+    exit 1
+fi
+
+$dwnld_cmd https://github.com/nathanchance/env/tarball/main | tar -C "$tmp_dir" -xvzf - --strip-components=1
+
+python_root=$tmp_dir/python/root
+if [ ! -d "$python_root" ]; then
+    echo "[-] $python_root could not be found, did download command fail?" >&2
+    exit 1
+fi
+
+for file in /etc/os-release /usr/lib/os-release; do
+    # We don't care if this fails, we will fail on the next command
+    if . $file >/dev/null 2>&1; then
+        break
+    fi
+done
+
+if ! is_available python3; then
+    if is_available apk; then
+        apk add python3
+    else
+        echo "[-] No suitable command could be found to install python3" >&2
+    fi
+fi
+
+"$python_root"/"$ID".py "$@"