use a $TAIL_PATH env for 'tail' command

The command 'tail' was aliased to 'colortail' in my local environment
and 'colortail' was not installed locally, so it failed during setting
up the 'cd' and '__gvm_oldcd' functions. This caused the 'cd' command
to silently do nothing and never change directories.

Author: brianonn

scripts/env/cd

@@ -12,12 +12,12 @@
 if __gvm_is_function __gvm_oldcd; then
     # output from declare -f on zsh omits a newline before opening brace, so
     # we need to add the newline for consistency with bash.
-    eval "$(echo "cd()"; declare -f __gvm_oldcd | sed '1 s/{/\'$'\n''{/' | tail -n +2)"
+    eval "$(echo "cd()"; declare -f __gvm_oldcd | sed '1 s/{/\'$'\n''{/' | $TAIL_PATH -n +2)"
     unset -f __gvm_oldcd
 fi
 
 if __gvm_is_function cd; then
-    eval "$(echo "__gvm_oldcd()"; declare -f cd | sed '1 s/{/\'$'\n''{/' | tail -n +2)"
+    eval "$(echo "__gvm_oldcd()"; declare -f cd | sed '1 s/{/\'$'\n''{/' | $TAIL_PATH -n +2)"
 elif [[ "$(builtin type cd)" == "cd is a shell builtin" ]]; then
     eval "$(echo "__gvm_oldcd() { builtin cd \$*; return \$?; }")"
 fi

scripts/function/tools

@@ -6,6 +6,7 @@ GREP_ERROR="GVM couldn't find grep"
 EGREP_ERROR="GVM couldn't find egrep"
 SORT_ERROR="GVM couldn't find sort"
 HEAD_ERROR="GVM couldn't find head"
+TAIL_ERROR="GVM couldn't find tail"
 HEXDUMP_ERROR="GVM couldn't find hexdump"
 
 LS_PATH=$(unalias ls &> /dev/null; command -v ls) || display_error "$LS_ERROR" || return 1
@@ -15,4 +16,5 @@ GREP_PATH=$(unalias grep &> /dev/null; command -v grep) || display_error "$GREP_
 EGREP_PATH=$(unalias egrep &> /dev/null; command -v egrep) || display_error "$EGREP_ERROR" || return 1
 SORT_PATH=$(unalias sort &> /dev/null; command -v sort) || display_error "$SORT_ERROR" || return 1
 HEAD_PATH=$(unalias head &> /dev/null; command -v head) || display_error "$HEAD_ERROR" || return 1
+TAIL_PATH=$(unalias tail &> /dev/null; command -v tail) || display_error "$TAIL_ERROR" || return 1
 HEXDUMP_PATH=$(unalias hexdump &> /dev/null; command -v hexdump) || display_error "$HEXDUMP_ERROR" || return 1