feat(ssh): Load hosts in other ssh config files

If the ~/.ssh/config contains `Include` directives, it'd be better
to parse the target config files if possible. This commit implements that.
The included config can also have Include directives, but it's not parsed
because of possibility of infinite loop, for now.

plugins/ssh/README.md

@@ -1,7 +1,8 @@
 # ssh plugin
 
-This plugin provides host completion based off of your `~/.ssh/config` file, and adds
-some utility functions to work with SSH keys.
+This plugin provides host completion based off of your `~/.ssh/config` file,
+and adds some utility functions to work with SSH keys. If the `~/.ssh/config`
+contains `Include` directives, the plugin also parse hosts in related files.
 
 To use it, add `ssh` to the plugins array in your zshrc file:
 

plugins/ssh/ssh.plugin.zsh

@@ -2,20 +2,53 @@
 # Take all host sections in .ssh/config and offer them for
 # completion as hosts (e.g. for ssh, rsync, scp and the like)
 # Filter out wildcard host sections.
-_ssh_configfile="$HOME/.ssh/config"
-if [[ -f "$_ssh_configfile" ]]; then
-  _ssh_hosts=($(
-    grep -E '^Host.*' "$_ssh_configfile" |\
+# If the .ssh/config has Include directives, load them too.
+function _load_ssh_hosts {
+  local conf="$1"
+  if [[ -f "$conf" ]]; then
+    local _ssh_hosts=($(
+      grep -E '^Host[[:space:]]' "$conf" |\
+      awk '{for (i=2; i<=NF; i++) print $i}' |\
+      sort |\
+      uniq |\
+      grep -v '^*' |\
+      sed -e 's/\.*\*$//'
+    ))
+    echo "${_ssh_hosts[@]}"
+  fi
+}
+
+# XXX: We could make it recursive but won't implement for now
+function _find_include_files {
+  local conf="$1"
+  if [[ -f "$conf" ]]; then
+    grep -E '^Include[[:space:]]' "$conf" |\
     awk '{for (i=2; i<=NF; i++) print $i}' |\
-    sort |\
-    uniq |\
-    grep -v '^*' |\
-    sed -e 's/\.*\*$//'
-  ))
-  zstyle ':completion:*:hosts' hosts $_ssh_hosts
-  unset _ssh_hosts
-fi
-unset _ssh_configfile
+    sed -e 's/^"\(.*\)"$/\1/' -e "s/^'\(.*\)'\$/\\1/"
+  fi
+}
+
+all_hosts=($(_load_ssh_hosts "$HOME/.ssh/config"))
+
+_find_include_files "$HOME/.ssh/config" | while read include_file; do
+  # omz doesn't know "~" directory
+  if [[ "$include_file" == ~* ]]; then
+    include_file="${HOME}${include_file:1}"
+  # Per ssh_config(5), relative paths are resolved against ~/.ssh
+  elif [[ "$include_file" != /* ]]; then
+    include_file="$HOME/.ssh/$include_file"
+  fi
+  if [[ -f "$include_file" ]]; then
+    hosts=($(_load_ssh_hosts "$include_file"))
+    all_hosts+=("${hosts[@]}")
+  fi
+done
+
+zstyle ':completion:*:hosts' hosts "${all_hosts[@]}"
+
+unset -f _load_ssh_hosts
+unset -f _find_include_files
+unset all_hosts
 
 ############################################################
 # Remove host key from known hosts based on a host section