Add startswith and endswith function

This is helpful in places where you need to use variables in the string
which needs to be compare e.g. something like this:

```puppet
$test.startswith("part${string}01")
```

Author: baurmatt

lib/puppet/functions/endswith.rb

@@ -0,0 +1,23 @@
+# @summary
+#   Returns true if str ends with one of the prefixes given. Each of the prefixes should be a String.
+#
+# @example endswith(String, String)
+#   endswith('foobar', 'bar') => true
+#
+# @example startswith(String, ['bar', 'baz'])
+#   endswith('foobar', ['foo', 'baz']) => false
+#
+Puppet::Functions.create_function(:endswith) do
+  # @param str The string to check
+  # @param prefixes The pattern or string to check against.
+  # @return [Boolean] True or False
+  dispatch :endswith do
+    param 'String', :str
+    param 'Variant[String,Array[String, 1]]', :prefixes
+    return_type 'Boolean'
+  end
+
+  def endswith(str, prefixes)
+    str.end_with?(*prefixes)
+  end
+end

lib/puppet/functions/startswith.rb

@@ -0,0 +1,23 @@
+# @summary
+#   Returns true if str starts with one of the prefixes given. Each of the prefixes should be a String or a Regexp.
+#
+# @example startswith(String, String)
+#   startswith('foobar', 'foo') => true
+#
+# @example startswith(String, ['bar', 'baz'])
+#   startswith('foObar', ['bar', 'baz']) => false
+#
+Puppet::Functions.create_function(:startswith) do
+  # @param str The string to check
+  # @param prefixes The pattern or string to check against.
+  # @return [Boolean] True or False
+  dispatch :startswith do
+    param 'String', :str
+    param 'Variant[String,Array[String, 1]]', :prefixes
+    return_type 'Boolean'
+  end
+
+  def startswith(str, prefixes)
+    str.start_with?(*prefixes)
+  end
+end

spec/functions/endswith_spec.rb

@@ -0,0 +1,10 @@
+require 'spec_helper'
+
+describe 'endswith' do
+  it { is_expected.not_to eq(nil) }
+  it { is_expected.to run.with_params.and_raise_error(ArgumentError, %r{expects 2 arguments, got none}i) }
+  it { is_expected.to run.with_params('').and_raise_error(ArgumentError, %r{expects 2 arguments, got 1}) }
+
+  it { is_expected.to run.with_params('foobar', 'bar').and_return(true) }
+  it { is_expected.to run.with_params('foobar', ['foo', 'baz']).and_return(false) }
+end

spec/functions/startswith_spec.rb

@@ -0,0 +1,10 @@
+require 'spec_helper'
+
+describe 'startswith' do
+  it { is_expected.not_to eq(nil) }
+  it { is_expected.to run.with_params.and_raise_error(ArgumentError, %r{expects 2 arguments, got none}i) }
+  it { is_expected.to run.with_params('').and_raise_error(ArgumentError, %r{expects 2 arguments, got 1}) }
+
+  it { is_expected.to run.with_params('foobar', 'foo').and_return(true) }
+  it { is_expected.to run.with_params('foObar', ['bar', 'baz']).and_return(false) }
+end