Fix for initial commit and remove unneeded args

app/controllers/concerns/creates_commit.rb

@@ -4,9 +4,10 @@ module CreatesCommit
   def create_commit(service, success_path:, failure_path:, failure_view: nil, success_notice: nil)
     set_commit_variables
 
+    source_branch = @mr_target_branch unless initial_commit?
     commit_params = @commit_params.merge(
       source_project: @mr_target_project,
-      source_branch: @mr_target_branch,
+      source_branch: source_branch,
       target_branch: @mr_source_branch
     )
 
@@ -113,7 +114,7 @@ module CreatesCommit
       else
         # Merge request to this project
         @mr_target_project = @project
-        @mr_target_branch ||= @ref
+        @mr_target_branch = @ref || @target_branch
       end
     else
       # Edit file in fork
@@ -121,7 +122,12 @@ module CreatesCommit
       # Merge request from fork to this project
       @mr_source_project = @tree_edit_project
       @mr_target_project = @project
-      @mr_target_branch ||= @ref
+      @mr_target_branch = @ref || @target_branch
     end
   end
+
+  def initial_commit?
+    @mr_target_branch.nil? ||
+      !@mr_target_project.repository.branch_exists?(@mr_target_branch)
+  end
 end

app/services/commits/change_service.rb

@@ -26,8 +26,15 @@ module Commits
     def commit_change(action)
       raise NotImplementedError unless repository.respond_to?(action)
 
-      into = @create_merge_request ? @commit.public_send("#{action}_branch_name") : @target_branch
-      tree_id = repository.public_send("check_#{action}_content", @commit, @target_branch)
+      if @create_merge_request
+        into = @commit.public_send("#{action}_branch_name")
+        tree_branch = @source_branch
+      else
+        into = tree_branch = @target_branch
+      end
+
+      tree_id = repository.public_send(
+        "check_#{action}_content", @commit, tree_branch)
 
       if tree_id
         validate_target_branch(into) if @create_merge_request

lib/api/commits.rb

@@ -140,8 +140,6 @@ module API
         commit_params = {
           commit: commit,
           create_merge_request: false,
-          source_project: user_project,
-          source_branch: commit.cherry_pick_branch_name,
           target_branch: params[:branch]
         }