Drop support for Ruby 2.0, 2.1, 2.2, 2.3, and 2.4 (#549)

Already, the latest version of the sshkit gem is no longer installable
on Ruby 2.2 or older. See #548.

Rather than add workarounds to the sshkit code to restore compatibility
with old versions of Ruby, we've decided to officially drop support for
them.

This PR drops support for Ruby 2.0, 2.1, 2.2, 2.3, and 2.4. For
reference, Ruby 2.4 was officially EOL'd 4 years and 9 months ago (31
Mar 2020), so it is not unreasonable for us to drop support in 2025.

If users wish to use the sshkit gem on an old version of Ruby, they can
still do so by installing an older version. For example, 1.22.0 works on
Ruby 2.2.

```
gem install sshkit -v 1.22.0
```

Author: mattbrictson

.github/workflows/ci.yml

@@ -8,20 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby:
-          [
-            "2.3",
-            "2.4",
-            "2.5",
-            "2.6",
-            "2.7",
-            "3.0",
-            "3.1",
-            "3.2",
-            "3.3",
-            "3.4",
-            "head",
-          ]
+        ruby: ["2.5", "2.6", "2.7", "3.0", "3.1", "3.2", "3.3", "3.4", "head"]
     steps:
       - uses: actions/checkout@v4
       - name: Set up Ruby
@@ -34,24 +21,9 @@ jobs:
         env:
           RUBYOPT: ${{ startsWith(matrix.ruby, 'head') && '--enable=frozen-string-literal' || '' }}
 
-  test-legacy:
-    runs-on: ubuntu-20.04
-    strategy:
-      matrix:
-        ruby: ["2.0", "2.1", "2.2"]
-    steps:
-      - uses: actions/checkout@v4
-      - name: Set up Ruby
-        uses: ruby/setup-ruby@v1
-        with:
-          ruby-version: ${{ matrix.ruby }}
-          bundler-cache: true
-      - name: Run tests
-        run: bundle exec rake test:units
-
   test-all:
     runs-on: ubuntu-latest
-    needs: [test, test-legacy]
+    needs: test
     if: always()
     steps:
       - name: All tests ok
@@ -77,7 +49,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby: ["2.0", "ruby"]
+        ruby: ["2.5", "ruby"]
     steps:
       - uses: actions/checkout@v4
       - name: Set up Ruby

.rubocop.yml

@@ -3,7 +3,7 @@ inherit_from: .rubocop_todo.yml
 AllCops:
   DisplayCopNames: true
   DisplayStyleGuide: true
-  TargetRubyVersion: 2.0
+  TargetRubyVersion: 2.5
 
 Lint/AmbiguousBlockAssociation:
   Enabled: false
@@ -18,12 +18,12 @@ Style/ClassAndModuleChildren:
   Enabled: false
 Style/DoubleNegation:
   Enabled: false
-Style/FileName:
+Naming/FileName:
   Exclude:
     - "Dangerfile"
-Style/IndentHeredoc:
+Layout/IndentHeredoc:
   Enabled: false
-Style/SpaceAroundEqualsInParameterDefault:
+Layout/SpaceAroundEqualsInParameterDefault:
   EnforcedStyle: no_space
 Style/StringLiterals:
   EnforcedStyle: double_quotes
@@ -47,7 +47,7 @@ Metrics/CyclomaticComplexity:
   Enabled: false
 Metrics/MethodLength:
   Enabled: false
-Style/PredicateName:
+Naming/PredicateName:
   Enabled: false
 Metrics/LineLength:
   Enabled: false
@@ -59,5 +59,5 @@ Metrics/ClassLength:
   Enabled: false
 Metrics/ModuleLength:
   Enabled: false
-Style/AccessorMethodName:
+Naming/AccessorMethodName:
   Enabled: false

.rubocop_todo.yml

@@ -439,7 +439,7 @@ Style/MethodDefParentheses:
 # Offense count: 3
 # Configuration parameters: SupportedStyles.
 # SupportedStyles: snake_case, camelCase
-Style/MethodName:
+Naming/MethodName:
   EnforcedStyle: snake_case
   Exclude:
     - 'test/unit/test_color.rb'
@@ -460,7 +460,7 @@ Style/NumericPredicate:
     - 'lib/sshkit/command.rb'
 
 # Offense count: 1
-Style/OpMethod:
+Naming/BinaryOperatorParameterName:
   Exclude:
     - 'lib/sshkit/host.rb'
 
@@ -611,7 +611,7 @@ Style/UnneededPercentQ:
 # Offense count: 1
 # Configuration parameters: EnforcedStyle, SupportedStyles.
 # SupportedStyles: snake_case, normalcase, non_integer
-Style/VariableNumber:
+Naming/VariableNumber:
   Exclude:
     - 'test/unit/backends/test_connection_pool.rb'
 

Gemfile

@@ -1,8 +1,3 @@
 source 'https://rubygems.org'
 
 gemspec
-
-# public_suffix 3+ requires ruby 2.1+
-if Gem::Requirement.new('< 2.1').satisfied_by?(Gem::Version.new(RUBY_VERSION))
-  gem 'public_suffix', '< 3'
-end

RELEASING.md

@@ -4,7 +4,7 @@
 
 * You must have commit rights to the SSHKit repository.
 * You must have push rights for the sshkit gem on rubygems.org.
-* You must be using Ruby >= 2.1.0.
+* You must be using Ruby >= 2.5.0.
 
 ## How to release
 

lib/sshkit/backends/abstract.rb

@@ -135,8 +135,7 @@ def configure
       # Backends which extend the Abstract backend should implement the following methods:
       def upload!(_local, _remote, _options = {}) raise MethodUnavailableError end
       def download!(_remote, _local=nil, _options = {}) raise MethodUnavailableError end
-      def execute_command(_cmd) raise MethodUnavailableError end
-      private :execute_command # Can inline after Ruby 2.1
+      private def execute_command(_cmd) raise MethodUnavailableError end
 
       private
 

lib/sshkit/backends/connection_pool.rb

@@ -1,5 +1,4 @@
 require "monitor"
-require "thread"
 
 # Since we call to_s on new connection arguments and use that as a cache key, we
 # need to make sure the memory address of the object is not used as part of the

lib/sshkit/runners/parallel.rb

@@ -1,5 +1,3 @@
-require 'thread'
-
 module SSHKit
 
   module Runner

sshkit.gemspec

@@ -19,19 +19,20 @@ Gem::Specification.new do |gem|
   gem.name          = "sshkit"
   gem.require_paths = ["lib"]
   gem.version       = SSHKit::VERSION
+  gem.required_ruby_version = ">= 2.5"
 
-  gem.add_runtime_dependency('base64') if RUBY_VERSION >= "2.4"
+  gem.add_runtime_dependency('base64')
   gem.add_runtime_dependency('net-ssh',  '>= 2.8.0')
   gem.add_runtime_dependency('net-scp',  '>= 1.1.2')
   gem.add_runtime_dependency('net-sftp', '>= 2.1.2')
-  gem.add_runtime_dependency('ostruct') if RUBY_VERSION >= "2.5"
+  gem.add_runtime_dependency('ostruct')
 
   gem.add_development_dependency('danger')
   gem.add_development_dependency('minitest', '>= 5.0.0')
   gem.add_development_dependency('minitest-reporters')
   gem.add_development_dependency('rainbow', '~> 2.2.2')
   gem.add_development_dependency('rake')
-  gem.add_development_dependency('rubocop', "~> 0.49.1")
+  gem.add_development_dependency('rubocop', "~> 0.52.0")
   gem.add_development_dependency('mocha')
 
   gem.add_development_dependency('bcrypt_pbkdf')

test/functional/backends/test_netssh.rb

@@ -131,7 +131,7 @@ def test_execute_raises_on_non_zero_exit_status_and_captures_stdout_and_stderr
 
       def test_test_does_not_raise_on_non_zero_exit_status
         Netssh.new(a_host) do |_host|
-          test :false
+          test :false # rubocop:disable Lint/BooleanSymbol
         end.run
       end
 
@@ -151,7 +151,7 @@ def test_connection_pool_keepalive
         # ensure we enable connection pool
         SSHKit::Backend::Netssh.pool.idle_timeout = 10
         Netssh.new(a_host) do |_host|
-          test :false
+          test :false # rubocop:disable Lint/BooleanSymbol
         end.run
         sleep 2.5
         captured_command_result = nil