Add ssh_fingerprint (and ssh_fp alias)

Also update README.md

plugins/ssh/ssh.plugin.zsh

@@ -51,3 +51,35 @@ function ssh_unload_key {
     ssh-add -d "$keyfile"
   fi
 }
+
+############################################################
+# Calculate SSH key fingerprint
+function ssh_fingerprint {
+  local fptype
+  local quiet
+  local ansi
+
+  zmodload zsh/zutil
+  zparseopts -D -- md5=fptype q=quiet n=ansi
+  fptype="${fptype[*]}"
+  if [[ -z $fptype ]]; then
+    fptype="sha256"
+  else
+    fptype="${fptype:1}"
+  fi
+  if [[ -z ${ansi[*]} ]]; then
+    ansi=("\e[1;30m" "\e[0m")
+  else
+    ansi=("" "")
+  fi
+
+  local keyfiles=( "$@" )
+  if [[ ${#keyfiles[@]} == 0 ]]; then keyfiles=( "$HOME/.ssh/authorized_keys" ); fi
+  local f
+  for f in "${keyfiles[@]}"; do
+    if [[ $quiet != "-q" ]]; then printf "${ansi[1]}$f:${ansi[2]}\n"; fi
+    ssh-keygen -l -E "$fptype" -f "$f"
+  done
+}
+alias ssh_fp='ssh_fingerprint'
+