zsh: functions: add bak/unbak functions

functions/misc.zsh

@@ -367,6 +367,16 @@ function watchc() {
     watch --differences --interval 1 --color grc --colour=on $@
 }
 
+# make a backup copy of the argument adding the .bak suffix
+function bak() {
+    cp $1{,.bak}
+}
+
+# restore a backup copy created using `bak`
+function unbak() {
+    mv $1{.bak,}
+}
+
 # highlight functions with when calling which
 function which(){
     if ! (($+commands[bat])); then