Use separate error class for cherry-pick and revert tree errors

app/models/repository.rb

@@ -6,6 +6,7 @@ class Repository
   attr_accessor :path_with_namespace, :project
 
   CommitError = Class.new(StandardError)
+  CreateTreeError = Class.new(StandardError)
 
   # Methods that cache data from the Git repository.
   #
@@ -871,7 +872,7 @@ class Repository
 
       revert_tree_id = check_revert_content(commit, start_commit.sha)
       unless revert_tree_id
-        raise Repository::CommitError.new('Failed to revert commit')
+        raise Repository::CreateTreeError.new('Failed to revert commit')
       end
 
       committer = user_to_committer(user)
@@ -895,7 +896,7 @@ class Repository
 
       cherry_pick_tree_id = check_cherry_pick_content(commit, start_commit.sha)
       unless cherry_pick_tree_id
-        raise Repository::CommitError.new('Failed to cherry-pick commit')
+        raise Repository::CreateTreeError.new('Failed to cherry-pick commit')
       end
 
       committer = user_to_committer(user)

app/services/commits/change_service.rb

@@ -37,14 +37,10 @@ module Commits
         start_branch_name: @start_branch)
 
       success
-    rescue Repository::CommitError => e
-      if e.message =~ /Failed to/
+    rescue Repository::CreateTreeError => e
       error_msg = "Sorry, we cannot #{action.to_s.dasherize} this #{@commit.change_type_title(current_user)} automatically.
                      A #{action.to_s.dasherize} may have already been performed with this #{@commit.change_type_title(current_user)}, or a more recent commit may have updated some of its content."
       raise ChangeError, error_msg
-      else
-        raise
-      end
     end
 
     def check_push_permissions
@@ -58,8 +54,8 @@ module Commits
     end
 
     def validate_target_branch
-      result = ValidateNewBranchService.new(@project, current_user).
-        execute(@target_branch)
+      result = ValidateNewBranchService.new(@project, current_user)
+        .execute(@target_branch)
 
       if result[:status] == :error
         raise ChangeError, "There was an error creating the source branch: #{result[:message]}"