otp: add README and use clipcopy

plugins/otp/README.md

+# otp plugin
+
+This plugin allows you to create one-time passwords using [`oathtool`](https://www.nongnu.org/oath-toolkit/man-oathtool.html),
+able to replace MFA devices. The oathtool key is kept in a GPG-encrypted file so the codes
+can only be generated by a user able to decrypt it.
+
+To use it, add `otp` to the plugins array in your zshrc file:
+```zsh
+plugins=(... otp)
+```
+
+Provided aliases:
+
+- `otp_add_device`: creates a new encrypted storage for an oathtool key and stores it
+  on the disk. For encrypting the key, it will ask for a GPG user ID (your GPG key's
+  email address). Then the OTP key needs to be pasted, followed by a CTRL+D character
+  inserted on an empty line.
+
+- `ot`: generates a MFA code based on the given key and copies it to the clipboard 
+  (on Linux it relies on xsel, on MacOS X it uses pbcopy instead).
+
+The plugin uses `$HOME/.otp` to store its internal files.

plugins/otp/otp.plugin.zsh

@@ -12,32 +12,23 @@ function ot () {
     return 1
   fi
 
-  if [[ `uname` == 'Darwin' ]] then # MacOS X
-    export COPY_CMD='pbcopy'
-  elif command -v xsel > /dev/null 2>&1; then # Any Unix with xsel installed
-    export COPY_CMD='xsel --clipboard --input'
-  else
   COPY_CMD='true'
-  fi
 
-  if [[ "x$1" == "x" ]]; then
-    echo "usage: otpw <profile.name>"
+  if [[ -z "$1" ]]; then
+    echo "usage: $0 <profile.name>"
     return 1
   elif [ ! -f $OTP_HOME/$1.otp.asc ]; then
     echo "missing profile $1, you might need to create it first using otp_add_device"
     return 1
   else
     totpkey=$(gpg --decrypt $OTP_HOME/$1.otp.asc)
-    oathtool --totp --b $totpkey | tee /dev/stderr | `echo $COPY_CMD`
-    if [[ $COPY_CMD == 'true' ]] then
-      echo "Note: you might consider installing xsel for clipboard integration"
-    fi
+    oathtool --totp --b $totpkey | tee /dev/stderr | clipcopy
   fi
 }
 
 function otp_add_device () {
   if [[ "x$1" == "x" ]] then
-    echo "usage: otp_add <profile.name>"
+    echo "usage: $0 <profile.name>"
     return 1
   else
     echo "Enter an email address attached to your GPG private key, then paste the secret configuration key followed by ^D"