plugins/base: use _command_exists

Addresses #1632

plugins/available/base.plugin.bash

@@ -6,10 +6,10 @@ function ips ()
 {
     about 'display all ip addresses for this host'
     group 'base'
-    if command -v ifconfig &>/dev/null
+    if _command_exists ifconfig
     then
         ifconfig | awk '/inet /{ gsub(/addr:/, ""); print $2 }'
-    elif command -v ip &>/dev/null
+    elif _command_exists ip
     then
         ip addr | grep -oP 'inet \K[\d.]+'
     else
@@ -75,12 +75,12 @@ function passgen ()
 
 # Create alias pass to passgen when pass isn't installed or
 # BASH_IT_LEGACY_PASS is true.
-if ! command -v pass &>/dev/null || [[ "${BASH_IT_LEGACY_PASS:-}" = "true" ]]
+if ! _command_exists pass || [[ "${BASH_IT_LEGACY_PASS:-}" = true ]]
 then
   alias pass=passgen
 fi
 
-if type -t markdown >/dev/null && type -t browser >/dev/null
+if _command_exists markdown && _command_exists browser
 then pmdown ()
 {
     about 'preview markdown file in a browser'
@@ -151,17 +151,9 @@ then
     }
 fi
 
-function command_exists ()
-{
-    about 'checks for existence of a command'
-    param '1: command to check'
-    example '$ command_exists ls && echo exists'
-    group 'base'
-    type -t "$1" >/dev/null
-}
-
-if type -t mkisofs >/dev/null
-then mkiso ()
+if _command_exists mkisofs
+then
+function mkiso ()
 {
     about 'creates iso from current dir in the parent dir (unless defined)'
     param '1: ISO name'
@@ -195,8 +187,9 @@ function buf ()
     cp -a "${filename}" "${filename}_${filetime}"
 }
 
-if ! type -t del >/dev/null
-then del() {
+if ! _command_exists del
+then
+function del() {
     about 'move files to hidden folder in tmp, that gets cleared on each reboot'
     param 'file or folder to be deleted'
     example 'del ./file.txt'