Improve offense messages

Make it a bit more clearer as to what's
problematic and what to do intead of those
lines of code.

Signed-off-by: Utkarsh Gupta <utkarsh@debian.org>

config/default.yml

@@ -1,25 +1,36 @@
 # This is the default configuration file.
 
 Packaging/BundlerSetupInTests:
-  Description: 'Avoid using `bundler/setup` in your tests.'
+  Description: >-
+                 Using `bundler/setup` in tests is redundant. Consider
+                 removing it.
   Enabled: true
   VersionAdded: '0.4'
   VersionChanged: '0.5'
 
 Packaging/GemspecGit:
-  Description: 'Use pure Ruby alternative instead of `git ls-files`.'
+  Description: >-
+                 Using `bundler/setup` in tests is redundant. Consider
+                 Avoid using git to produce lists of files. Downstreams
+                 often need to build your package in an environment
+                 that does not have git (on purpose). Use some pure
+                 Ruby alternative, like `Dir` or `Dir.glob`.
   Enabled: true
   VersionAdded: '0.1'
   VersionChanged: '0.1'
 
 Packaging/RequireHardcodingLib:
-  Description: 'Avoid using `require` with relative path to lib.'
+  Description: >-
+                 Avoid using `require` with relative path to lib. Use
+                 `require` with absolute path instead.
   Enabled: true
   VersionAdded: '0.4'
   VersionChanged: '0.5'
 
 Packaging/RequireRelativeHardcodingLib:
-  Description: 'Avoid using `require_relative` with relative path to lib.'
+  Description: >-
+                 Avoid using `require_relative` with relative path to
+                 lib. Use `require` with absolute path instead.
   Enabled: true
   VersionAdded: '0.2'
   VersionChanged: '0.5'

lib/rubocop/cop/packaging/bundler_setup_in_tests.rb

@@ -24,7 +24,7 @@ class BundlerSetupInTests < Base
 
         # This is the message that will be displayed when RuboCop::Packaging finds
         # an offense of using `require "bundler/setup"` in the tests directory.
-        MSG = "Avoid using `bundler/setup` in your tests."
+        MSG = "Using `bundler/setup` in tests is redundant. Consider removing it."
 
         def_node_matcher :bundler_setup?, <<~PATTERN
           (send nil? :require

lib/rubocop/cop/packaging/gemspec_git.rb

@@ -53,9 +53,9 @@ class GemspecGit < Base
         # This is the message that will be displayed when RuboCop finds an
         # offense of using `git ls-files`.
         MSG = "Avoid using git to produce lists of files. " \
-          "Downstreams often need to build your package in an environment " \
-          "that does not have git (on purpose). " \
-          "Use some pure Ruby alternative, like `Dir` or `Dir.glob`."
+              "Downstreams often need to build your package in an environment " \
+              "that does not have git (on purpose). " \
+              "Use some pure Ruby alternative, like `Dir` or `Dir.glob`."
 
         def_node_search :xstr, <<~PATTERN
           (block

lib/rubocop/cop/packaging/require_hardcoding_lib.rb

@@ -40,7 +40,8 @@ class RequireHardcodingLib < Base
 
         # This is the message that will be displayed when RuboCop::Packaging
         # finds an offense of using `require` with relative path to lib.
-        MSG = "Avoid using `require` with relative path to `lib/`."
+        MSG = "Avoid using `require` with relative path to `lib/`. " \
+              "Use `require` with absolute path instead."
 
         def_node_matcher :require?, <<~PATTERN
           {(send nil? :require (str #falls_in_lib?))

lib/rubocop/cop/packaging/require_relative_hardcoding_lib.rb

@@ -34,7 +34,7 @@ class RequireRelativeHardcodingLib < Base
         # This is the message that will be displayed when RuboCop finds an
         # offense of using `require_relative` with relative path to lib.
         MSG = "Avoid using `require_relative` with relative path to lib. " \
-          "Use `require` instead."
+              "Use `require` with absolute path instead."
 
         def_node_matcher :require_relative, <<~PATTERN
           (send nil? :require_relative