Busybox support (#3797)

* Added support for shells without default variable support

* Added support for BusyBox installs that do not have `command` but has `which`

* Style fixes as suggested by reviewer

* Renamed `WHERE_IS` to `EXISTS` as suggested by review

* Removed expansion of `$LE_AUTO_SUDO` to `x` as the `-n` can check empty strings.

* Added `EXISTS` to debian bootstrap as suggested in review

letsencrypt-auto-source/letsencrypt-auto.template

@@ -15,9 +15,13 @@ set -e  # Work even if somebody does "sh thisscript.sh".
 
 # Note: you can set XDG_DATA_HOME or VENV_PATH before running this script,
 # if you want to change where the virtual environment will be installed
-XDG_DATA_HOME=${XDG_DATA_HOME:-~/.local/share}
+if [ -z "$XDG_DATA_HOME" ]; then
+  XDG_DATA_HOME="~/.local/share"
+fi
 VENV_NAME="letsencrypt"
-VENV_PATH=${VENV_PATH:-"$XDG_DATA_HOME/$VENV_NAME"}
+if [ -z "$VENV_PATH" ]; then
+  VENV_PATH="$XDG_DATA_HOME/$VENV_NAME"
+fi
 VENV_BIN="$VENV_PATH/bin"
 LE_AUTO_VERSION="{{ LE_AUTO_VERSION }}"
 BASENAME=$(basename $0)
@@ -80,6 +84,17 @@ if [ $BASENAME = "letsencrypt-auto" ]; then
   HELP=0
 fi
 
+# Support for busybox and others where there is no "command",
+# but "which" instead
+if command -v command > /dev/null 2>&1 ; then
+  export EXISTS="command -v"
+elif which which > /dev/null 2>&1 ; then
+  export EXISTS="which"
+else
+  echo "Cannot find command nor which... please install one!"
+  exit 1
+fi
+
 # certbot-auto needs root access to bootstrap OS dependencies, and
 # certbot itself needs root access for almost all modes of operation
 # The "normal" case is that sudo is used for the steps that need root, but
@@ -127,7 +142,7 @@ if [ -n "${LE_AUTO_SUDO+x}" ]; then
   echo "Using preset root authorization mechanism '$LE_AUTO_SUDO'."
 else
   if test "`id -u`" -ne "0" ; then
-    if command -v sudo 1>/dev/null 2>&1; then
+    if $EXISTS sudo 1>/dev/null 2>&1; then
       SUDO=sudo
       SUDO_ENV="CERTBOT_AUTO=$0"
     else
@@ -157,7 +172,7 @@ ExperimentalBootstrap() {
 DeterminePythonVersion() {
   for LE_PYTHON in "$LE_PYTHON" python2.7 python27 python2 python; do
     # Break (while keeping the LE_PYTHON value) if found.
-    command -v "$LE_PYTHON" > /dev/null && break
+    $EXISTS "$LE_PYTHON" > /dev/null && break
   done
   if [ "$?" != "0" ]; then
     echo "Cannot find any Pythons; please install one!"

letsencrypt-auto-source/pieces/bootstrappers/deb_common.sh

@@ -101,7 +101,7 @@ BootstrapDebCommon() {
 
 
 
-  if ! command -v virtualenv > /dev/null ; then
+  if ! $EXISTS virtualenv > /dev/null ; then
     echo Failed to install a working \"virtualenv\" command, exiting
     exit 1
   fi