Pass source_branch properly for cherry-pick/revert

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7237/diffs#note_19210818

app/models/repository.rb

@@ -962,14 +962,16 @@ class Repository
     end
   end
 
-  def revert(user, commit, base_branch, revert_tree_id = nil)
+  def revert(
+    user, commit, base_branch, revert_tree_id = nil,
+    source_branch: nil, source_project: project)
     revert_tree_id ||= check_revert_content(commit, base_branch)
 
     return false unless revert_tree_id
 
     GitOperationService.new(user, self).with_branch(
       base_branch,
-      source_commit: commit) do
+      source_branch: source_branch, source_project: source_project) do
 
       source_sha = find_branch(base_branch).dereferenced_target.sha
       committer = user_to_committer(user)
@@ -983,14 +985,16 @@ class Repository
     end
   end
 
-  def cherry_pick(user, commit, base_branch, cherry_pick_tree_id = nil)
+  def cherry_pick(
+    user, commit, base_branch, cherry_pick_tree_id = nil,
+    source_branch: nil, source_project: project)
     cherry_pick_tree_id ||= check_cherry_pick_content(commit, base_branch)
 
     return false unless cherry_pick_tree_id
 
     GitOperationService.new(user, self).with_branch(
       base_branch,
-      source_commit: commit) do
+      source_branch: source_branch, source_project: source_project) do
 
       source_sha = find_branch(base_branch).dereferenced_target.sha
       committer = user_to_committer(user)

app/services/commits/change_service.rb

@@ -31,7 +31,14 @@ module Commits
       if tree_id
         validate_target_branch(into) if @create_merge_request
 
-        repository.public_send(action, current_user, @commit, into, tree_id)
+        repository.public_send(
+          action,
+          current_user,
+          @commit,
+          into,
+          tree_id,
+          source_branch: @target_branch)
+
         success
       else
         error_msg = "Sorry, we cannot #{action.to_s.dasherize} this #{@commit.change_type_title} automatically.

app/services/git_operation_service.rb

@@ -25,21 +25,15 @@ GitOperationService = Struct.new(:user, :repository) do
     end
   end
 
-  # Whenever `source_branch` or `source_commit` is passed, if `branch`
-  # doesn't exist, it would be created from `source_branch` or
-  # `source_commit`. Should only pass one of them, not both.
+  # Whenever `source_branch` is passed, if `branch` doesn't exist,
+  # it would be created from `source_branch`.
   # If `source_project` is passed, and the branch doesn't exist,
   # it would try to find the source from it instead of current repository.
   def with_branch(
     branch_name,
     source_branch: nil,
-    source_commit: nil,
     source_project: repository.project)
 
-    if source_commit && source_branch
-      raise ArgumentError, 'Should pass only :source_branch or :source_commit'
-    end
-
     ref = Gitlab::Git::BRANCH_REF_PREFIX + branch_name
     oldrev = Gitlab::Git::BLANK_SHA
 
@@ -62,13 +56,13 @@ GitOperationService = Struct.new(:user, :repository) do
           " #{source_project.path_with_namespace}")
       end
 
-    elsif source_commit || source_branch
-      newrev = (source_commit || repository.commit(source_branch)).try(:sha)
+    elsif source_branch
+      newrev = repository.commit(source_branch).try(:sha)
 
       unless newrev
         raise Repository::CommitError.new(
           "Cannot find branch #{branch_name} nor" \
-          " #{source_commit.try(:sha) || source_branch} from" \
+          " #{source_branch} from" \
           " #{repository.project.path_with_namespace}")
       end