Allow configuring to ignore history entries matching a pattern

Set ZSH_AUTOSUGGEST_HISTORY_IGNORE to a glob pattern to have the history
and match_prev_cmd suggestion strategies never make suggestions matching
that pattern.

For example, set to "cd *" to never suggest any `cd` commands from
history (see issues #340 and #425). Or set to "?(#c50,)" to never
suggest anything 50 characters or longer (see issue #429).

spec/strategies/match_prev_cmd_spec.rb

@@ -3,19 +3,32 @@ require 'strategies/special_characters_helper'
 describe 'the `match_prev_cmd` strategy' do
   let(:options) { ['ZSH_AUTOSUGGEST_STRATEGY=match_prev_cmd'] }
 
+  let(:history) { [
+    'echo what',
+    'ls foo',
+    'echo what',
+    'ls bar',
+    'ls baz',
+    'echo what'
+  ] }
+
   it 'suggests the last matching history entry after the previous command' do
-    with_history(
-      'echo what',
-      'ls foo',
-      'echo what',
-      'ls bar',
-      'ls baz',
-      'echo what'
-    ) do
+    with_history(*history) do
       session.send_string('ls')
       wait_for { session.content }.to eq('ls bar')
     end
   end
 
+  context 'when ZSH_AUTOSUGGEST_HISTORY_IGNORE is set to a pattern' do
+    let(:options) { ['ZSH_AUTOSUGGEST_STRATEGY=match_prev_cmd', 'ZSH_AUTOSUGGEST_HISTORY_IGNORE="* bar"'] }
+
+    it 'does not make suggestions that match the pattern' do
+      with_history(*history) do
+        session.send_string('ls')
+        wait_for { session.content }.to eq('ls foo')
+      end
+    end
+  end
+
   include_examples 'special characters'
 end