Expose initial_commit? to post-commit hooks

Change-Id: I8a0105a499eb1c3ad648f5feec85c1cbc09c2731
Reviewed-on: http://gerrit.causes.com/46927
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>
Tested-by: Shane da Silva <shane.dasilva@brigade.com>

Author: jawshooah

lib/overcommit/hook/post_commit/base.rb

@@ -5,6 +5,6 @@ module Overcommit::Hook::PostCommit
   class Base < Overcommit::Hook::Base
     extend Forwardable
 
-    def_delegators :@context, :modified_lines_in_file
+    def_delegators :@context, :modified_lines_in_file, :initial_commit?
   end
 end

lib/overcommit/hook_context/post_commit.rb

@@ -19,13 +19,11 @@ def modified_lines_in_file(file)
         Overcommit::GitRepo.extract_modified_lines(file, subcmd: subcmd)
     end
 
-    private
-
-    # Returns whether a previous commit exists on the current git branch.
+    # Returns whether the current git branch has only one commit.
     # @return [true,false]
-    def previous_commit?
-      return @previous_commit unless @previous_commit.nil?
-      @previous_commit = Overcommit::Utils.execute(%w[git rev-parse HEAD~]).success?
+    def initial_commit?
+      return @initial_commit unless @initial_commit.nil?
+      @initial_commit = !Overcommit::Utils.execute(%w[git rev-parse HEAD~]).success?
     end
   end
 end

spec/overcommit/hook_context/post_commit_spec.rb

@@ -113,4 +113,31 @@
       it { should == Set.new(1..3) }
     end
   end
+
+  describe '#initial_commit?' do
+    subject { context.initial_commit? }
+
+    context 'when a previous commit exists' do
+      around do |example|
+        repo do
+          `git commit --allow-empty -m "Initial commit"`
+          `git commit --allow-empty -m "Another commit"`
+          example.run
+        end
+      end
+
+      it { should == false }
+    end
+
+    context 'when no previous commit exists' do
+      around do |example|
+        repo do
+          `git commit --allow-empty -m "Initial commit"`
+          example.run
+        end
+      end
+
+      it { should == true }
+    end
+  end
 end