Load bundled gems on expected version (#859)

Fixes #789

`psych` is no longer a default gem, but current and old ruby still ships
with it. When we `require 'yaml'`, we activate that gem in whatever
version that is bundled with ruby. Later on, we load bundler, and we
`Bundler.setup`, which will then activate whatever version specified in
the lock file. More often than not, they might not match.

The approach in this PR is to strip the `yaml` dependency completely
from the hook scripts, while retaining the ability to configure the
Gemfile using it.

template-dir/hooks/commit-msg

@@ -27,14 +27,8 @@ if hook_type == 'overcommit-hook'
 end
 
 # Check if Overcommit should invoke a Bundler context for loading gems
-require 'yaml'
-# rubocop:disable Style/RescueModifier
-gemfile =
-  begin
-    YAML.load_file('.overcommit.yml', aliases: true)['gemfile']
-  rescue ArgumentError
-    YAML.load_file('.overcommit.yml')['gemfile']
-  end rescue nil
+config = File.read('.overcommit.yml') =~ /gemfile: ['"]?(.*)['"]?/
+gemfile = Regexp.last_match(1)
 
 if gemfile
   ENV['BUNDLE_GEMFILE'] = gemfile

template-dir/hooks/overcommit-hook

@@ -27,14 +27,8 @@ if hook_type == 'overcommit-hook'
 end
 
 # Check if Overcommit should invoke a Bundler context for loading gems
-require 'yaml'
-# rubocop:disable Style/RescueModifier
-gemfile =
-  begin
-    YAML.load_file('.overcommit.yml', aliases: true)['gemfile']
-  rescue ArgumentError
-    YAML.load_file('.overcommit.yml')['gemfile']
-  end rescue nil
+config = File.read('.overcommit.yml') =~ /gemfile: ['"]?(.*)['"]?/
+gemfile = Regexp.last_match(1)
 
 if gemfile
   ENV['BUNDLE_GEMFILE'] = gemfile

template-dir/hooks/post-checkout

@@ -27,14 +27,8 @@ if hook_type == 'overcommit-hook'
 end
 
 # Check if Overcommit should invoke a Bundler context for loading gems
-require 'yaml'
-# rubocop:disable Style/RescueModifier
-gemfile =
-  begin
-    YAML.load_file('.overcommit.yml', aliases: true)['gemfile']
-  rescue ArgumentError
-    YAML.load_file('.overcommit.yml')['gemfile']
-  end rescue nil
+config = File.read('.overcommit.yml') =~ /gemfile: ['"]?(.*)['"]?/
+gemfile = Regexp.last_match(1)
 
 if gemfile
   ENV['BUNDLE_GEMFILE'] = gemfile

template-dir/hooks/post-commit

@@ -27,14 +27,8 @@ if hook_type == 'overcommit-hook'
 end
 
 # Check if Overcommit should invoke a Bundler context for loading gems
-require 'yaml'
-# rubocop:disable Style/RescueModifier
-gemfile =
-  begin
-    YAML.load_file('.overcommit.yml', aliases: true)['gemfile']
-  rescue ArgumentError
-    YAML.load_file('.overcommit.yml')['gemfile']
-  end rescue nil
+config = File.read('.overcommit.yml') =~ /gemfile: ['"]?(.*)['"]?/
+gemfile = Regexp.last_match(1)
 
 if gemfile
   ENV['BUNDLE_GEMFILE'] = gemfile

template-dir/hooks/post-merge

@@ -27,14 +27,8 @@ if hook_type == 'overcommit-hook'
 end
 
 # Check if Overcommit should invoke a Bundler context for loading gems
-require 'yaml'
-# rubocop:disable Style/RescueModifier
-gemfile =
-  begin
-    YAML.load_file('.overcommit.yml', aliases: true)['gemfile']
-  rescue ArgumentError
-    YAML.load_file('.overcommit.yml')['gemfile']
-  end rescue nil
+config = File.read('.overcommit.yml') =~ /gemfile: ['"]?(.*)['"]?/
+gemfile = Regexp.last_match(1)
 
 if gemfile
   ENV['BUNDLE_GEMFILE'] = gemfile

template-dir/hooks/post-rewrite

@@ -27,14 +27,8 @@ if hook_type == 'overcommit-hook'
 end
 
 # Check if Overcommit should invoke a Bundler context for loading gems
-require 'yaml'
-# rubocop:disable Style/RescueModifier
-gemfile =
-  begin
-    YAML.load_file('.overcommit.yml', aliases: true)['gemfile']
-  rescue ArgumentError
-    YAML.load_file('.overcommit.yml')['gemfile']
-  end rescue nil
+config = File.read('.overcommit.yml') =~ /gemfile: ['"]?(.*)['"]?/
+gemfile = Regexp.last_match(1)
 
 if gemfile
   ENV['BUNDLE_GEMFILE'] = gemfile

template-dir/hooks/pre-commit

@@ -27,14 +27,8 @@ if hook_type == 'overcommit-hook'
 end
 
 # Check if Overcommit should invoke a Bundler context for loading gems
-require 'yaml'
-# rubocop:disable Style/RescueModifier
-gemfile =
-  begin
-    YAML.load_file('.overcommit.yml', aliases: true)['gemfile']
-  rescue ArgumentError
-    YAML.load_file('.overcommit.yml')['gemfile']
-  end rescue nil
+config = File.read('.overcommit.yml') =~ /gemfile: ['"]?(.*)['"]?/
+gemfile = Regexp.last_match(1)
 
 if gemfile
   ENV['BUNDLE_GEMFILE'] = gemfile

template-dir/hooks/pre-push

@@ -27,14 +27,8 @@ if hook_type == 'overcommit-hook'
 end
 
 # Check if Overcommit should invoke a Bundler context for loading gems
-require 'yaml'
-# rubocop:disable Style/RescueModifier
-gemfile =
-  begin
-    YAML.load_file('.overcommit.yml', aliases: true)['gemfile']
-  rescue ArgumentError
-    YAML.load_file('.overcommit.yml')['gemfile']
-  end rescue nil
+config = File.read('.overcommit.yml') =~ /gemfile: ['"]?(.*)['"]?/
+gemfile = Regexp.last_match(1)
 
 if gemfile
   ENV['BUNDLE_GEMFILE'] = gemfile

template-dir/hooks/pre-rebase

@@ -27,14 +27,8 @@ if hook_type == 'overcommit-hook'
 end
 
 # Check if Overcommit should invoke a Bundler context for loading gems
-require 'yaml'
-# rubocop:disable Style/RescueModifier
-gemfile =
-  begin
-    YAML.load_file('.overcommit.yml', aliases: true)['gemfile']
-  rescue ArgumentError
-    YAML.load_file('.overcommit.yml')['gemfile']
-  end rescue nil
+config = File.read('.overcommit.yml') =~ /gemfile: ['"]?(.*)['"]?/
+gemfile = Regexp.last_match(1)
 
 if gemfile
   ENV['BUNDLE_GEMFILE'] = gemfile

template-dir/hooks/prepare-commit-msg

@@ -27,14 +27,8 @@ if hook_type == 'overcommit-hook'
 end
 
 # Check if Overcommit should invoke a Bundler context for loading gems
-require 'yaml'
-# rubocop:disable Style/RescueModifier
-gemfile =
-  begin
-    YAML.load_file('.overcommit.yml', aliases: true)['gemfile']
-  rescue ArgumentError
-    YAML.load_file('.overcommit.yml')['gemfile']
-  end rescue nil
+config = File.read('.overcommit.yml') =~ /gemfile: ['"]?(.*)['"]?/
+gemfile = Regexp.last_match(1)
 
 if gemfile
   ENV['BUNDLE_GEMFILE'] = gemfile