Add start_sha to commits API

When passing start_branch on committing from the WebIDE, it's possible
that the branch has changed since editing started, which results in the
change being applied on top of the latest commit in the branch and
overwriting the new changes.

By passing the start_sha instead we can make sure that the change is
applied on top of the commit which the user started editing from.

1 files changed, 17 insertions, 1 deletions

diff --git a/app/services/commits/create_service.rb b/app/services/commits/create_service.rb
index bb34a3d3352..f3be68f9602 100644
--- a/app/services/commits/create_service.rb
+++ b/app/services/commits/create_service.rb
@@ -10,6 +10,7 @@ module Commits
 
       @start_project = params[:start_project] || @project
       @start_branch = params[:start_branch]
+      @start_sha = params[:start_sha]
       @branch_name = params[:branch_name]
       @force = params[:force] || false
     end
@@ -40,7 +41,7 @@ module Commits
     end
 
     def different_branch?
-      @start_branch != @branch_name || @start_project != @project
+      @start_project != @project || @start_branch != @branch_name || @start_sha.present?
     end
 
     def force?
@@ -49,6 +50,7 @@ module Commits
 
     def validate!
       validate_permissions!
+      validate_start_sha!
       validate_on_branch!
       validate_branch_existence!
 
@@ -63,7 +65,21 @@ module Commits
       end
     end
 
+    def validate_start_sha!
+      return unless @start_sha
+
+      if @start_branch
+        raise_error("You can't pass both start_branch and start_sha")
+      elsif !Gitlab::Git.commit_id?(@start_sha)
+        raise_error("Invalid start_sha '#{@start_sha}'")
+      elsif !@start_project.repository.commit(@start_sha)
+        raise_error("Cannot find start_sha '#{@start_sha}'")
+      end
+    end
+
     def validate_on_branch!
+      return unless @start_branch
+
       if !@start_project.empty_repo? && !@start_project.repository.branch_exists?(@start_branch)
         raise_error('You can only create or edit files when you are on a branch')
       end