diff --git a/app/controllers/concerns/creates_commit.rb b/app/controllers/concerns/creates_commit.rb
index 258791bb5cd..c503f8bf696 100644
--- a/app/controllers/concerns/creates_commit.rb
+++ b/app/controllers/concerns/creates_commit.rb
@@ -4,10 +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?
+    base_branch = @mr_target_branch unless initial_commit?
     commit_params = @commit_params.merge(
-      source_project: @mr_target_project,
-      source_branch: source_branch,
+      base_project: @mr_target_project,
+      base_branch: base_branch,
       target_branch: @mr_source_branch
     )
 
diff --git a/app/models/repository.rb b/app/models/repository.rb
index e834936aa93..a335c629a78 100644
--- a/app/models/repository.rb
+++ b/app/models/repository.rb
@@ -748,12 +748,12 @@ class Repository
     user, path,
     message:, branch_name:,
     author_email: nil, author_name: nil,
-    source_branch_name: nil, source_project: project)
+    base_branch_name: nil, base_project: project)
     check_tree_entry_for_dir(branch_name, path)
 
-    if source_branch_name
-      source_project.repository.
-        check_tree_entry_for_dir(source_branch_name, path)
+    if base_branch_name
+      base_project.repository.
+        check_tree_entry_for_dir(base_branch_name, path)
     end
 
     commit_file(
@@ -765,8 +765,8 @@ class Repository
       update: false,
       author_email: author_email,
       author_name: author_name,
-      source_branch_name: source_branch_name,
-      source_project: source_project)
+      base_branch_name: base_branch_name,
+      base_project: base_project)
   end
   # rubocop:enable Metrics/ParameterLists
 
@@ -775,7 +775,7 @@ class Repository
     user, path, content,
     message:, branch_name:, update: true,
     author_email: nil, author_name: nil,
-    source_branch_name: nil, source_project: project)
+    base_branch_name: nil, base_project: project)
     unless update
       error_message = "Filename already exists; update not allowed"
 
@@ -783,8 +783,8 @@ class Repository
         raise Gitlab::Git::Repository::InvalidBlobName.new(error_message)
       end
 
-      if source_branch_name &&
-          source_project.repository.tree_entry_at(source_branch_name, path)
+      if base_branch_name &&
+          base_project.repository.tree_entry_at(base_branch_name, path)
         raise Gitlab::Git::Repository::InvalidBlobName.new(error_message)
       end
     end
@@ -795,8 +795,8 @@ class Repository
       branch_name: branch_name,
       author_email: author_email,
       author_name: author_name,
-      source_branch_name: source_branch_name,
-      source_project: source_project,
+      base_branch_name: base_branch_name,
+      base_project: base_project,
       actions: [{ action: :create,
                   file_path: path,
                   content: content }])
@@ -808,7 +808,7 @@ class Repository
     user, path, content,
     message:, branch_name:, previous_path:,
     author_email: nil, author_name: nil,
-    source_branch_name: nil, source_project: project)
+    base_branch_name: nil, base_project: project)
     action = if previous_path && previous_path != path
                :move
              else
@@ -821,8 +821,8 @@ class Repository
       branch_name: branch_name,
       author_email: author_email,
       author_name: author_name,
-      source_branch_name: source_branch_name,
-      source_project: source_project,
+      base_branch_name: base_branch_name,
+      base_project: base_project,
       actions: [{ action: action,
                   file_path: path,
                   content: content,
@@ -835,15 +835,15 @@ class Repository
     user, path,
     message:, branch_name:,
     author_email: nil, author_name: nil,
-    source_branch_name: nil, source_project: project)
+    base_branch_name: nil, base_project: project)
     multi_action(
       user: user,
       message: message,
       branch_name: branch_name,
       author_email: author_email,
       author_name: author_name,
-      source_branch_name: source_branch_name,
-      source_project: source_project,
+      base_branch_name: base_branch_name,
+      base_project: base_project,
       actions: [{ action: :delete,
                   file_path: path }])
   end
@@ -853,16 +853,16 @@ class Repository
   def multi_action(
     user:, branch_name:, message:, actions:,
     author_email: nil, author_name: nil,
-    source_branch_name: nil, source_project: project)
+    base_branch_name: nil, base_project: project)
     GitOperationService.new(user, self).with_branch(
       branch_name,
-      source_branch_name: source_branch_name,
-      source_project: source_project) do |source_commit|
+      base_branch_name: base_branch_name,
+      base_project: base_project) do |base_commit|
       index = rugged.index
 
-      parents = if source_commit
-                  index.read_tree(source_commit.raw_commit.tree)
-                  [source_commit.sha]
+      parents = if base_commit
+                  index.read_tree(base_commit.raw_commit.tree)
+                  [base_commit.sha]
                 else
                   []
                 end
@@ -910,8 +910,8 @@ class Repository
 
   def merge(user, merge_request, options = {})
     GitOperationService.new(user, self).with_branch(
-      merge_request.target_branch) do |source_commit|
-      our_commit = source_commit.sha
+      merge_request.target_branch) do |base_commit|
+      our_commit = base_commit.sha
       their_commit = merge_request.diff_head_sha
 
       raise 'Invalid merge target' unless our_commit
@@ -935,15 +935,15 @@ class Repository
 
   def revert(
     user, commit, branch_name, revert_tree_id = nil,
-    source_branch_name: nil, source_project: project)
+    base_branch_name: nil, base_project: project)
     revert_tree_id ||= check_revert_content(commit, branch_name)
 
     return false unless revert_tree_id
 
     GitOperationService.new(user, self).with_branch(
       branch_name,
-      source_branch_name: source_branch_name,
-      source_project: source_project) do |source_commit|
+      base_branch_name: base_branch_name,
+      base_project: base_project) do |base_commit|
 
       committer = user_to_committer(user)
 
@@ -952,21 +952,21 @@ class Repository
         author: committer,
         committer: committer,
         tree: revert_tree_id,
-        parents: [source_commit.sha])
+        parents: [base_commit.sha])
     end
   end
 
   def cherry_pick(
     user, commit, branch_name, cherry_pick_tree_id = nil,
-    source_branch_name: nil, source_project: project)
+    base_branch_name: nil, base_project: project)
     cherry_pick_tree_id ||= check_cherry_pick_content(commit, branch_name)
 
     return false unless cherry_pick_tree_id
 
     GitOperationService.new(user, self).with_branch(
       branch_name,
-      source_branch_name: source_branch_name,
-      source_project: source_project) do |source_commit|
+      base_branch_name: base_branch_name,
+      base_project: base_project) do |base_commit|
 
       committer = user_to_committer(user)
 
@@ -979,7 +979,7 @@ class Repository
         },
         committer: committer,
         tree: cherry_pick_tree_id,
-        parents: [source_commit.sha])
+        parents: [base_commit.sha])
     end
   end
 
@@ -1066,20 +1066,20 @@ class Repository
     Gitlab::Popen.popen(args, path_to_repo).first.lines.map(&:strip)
   end
 
-  def with_repo_branch_commit(source_repository, source_branch_name)
+  def with_repo_branch_commit(base_repository, base_branch_name)
     branch_name_or_sha =
-      if source_repository == self
-        source_branch_name
+      if base_repository == self
+        base_branch_name
       else
         tmp_ref = "refs/tmp/#{SecureRandom.hex}/head"
 
         fetch_ref(
-          source_repository.path_to_repo,
-          "#{Gitlab::Git::BRANCH_REF_PREFIX}#{source_branch_name}",
+          base_repository.path_to_repo,
+          "#{Gitlab::Git::BRANCH_REF_PREFIX}#{base_branch_name}",
           tmp_ref
         )
 
-        source_repository.commit(source_branch_name).sha
+        base_repository.commit(base_branch_name).sha
       end
 
     yield(commit(branch_name_or_sha))
diff --git a/app/services/commits/change_service.rb b/app/services/commits/change_service.rb
index 8d1dfbcea7d..1faa052e0ca 100644
--- a/app/services/commits/change_service.rb
+++ b/app/services/commits/change_service.rb
@@ -4,8 +4,8 @@ module Commits
     class ChangeError < StandardError; end
 
     def execute
-      @source_project = params[:source_project] || @project
-      @source_branch = params[:source_branch]
+      @base_project = params[:base_project] || @project
+      @base_branch = params[:base_branch]
       @target_branch = params[:target_branch]
       @commit = params[:commit]
       @create_merge_request = params[:create_merge_request].present?
@@ -28,7 +28,7 @@ module Commits
 
       if @create_merge_request
         into = @commit.public_send("#{action}_branch_name")
-        tree_branch = @source_branch
+        tree_branch = @base_branch
       else
         into = tree_branch = @target_branch
       end
@@ -45,8 +45,8 @@ module Commits
           @commit,
           into,
           tree_id,
-          source_project: @source_project,
-          source_branch_name: @source_branch)
+          base_project: @base_project,
+          base_branch_name: @base_branch)
 
         success
       else
diff --git a/app/services/compare_service.rb b/app/services/compare_service.rb
index d3d613661a6..2e4f8ee9dc8 100644
--- a/app/services/compare_service.rb
+++ b/app/services/compare_service.rb
@@ -3,18 +3,18 @@ require 'securerandom'
 # Compare 2 branches for one repo or between repositories
 # and return Gitlab::Git::Compare object that responds to commits and diffs
 class CompareService
-  attr_reader :source_project, :source_branch_name
+  attr_reader :base_project, :base_branch_name
 
-  def initialize(new_source_project, new_source_branch_name)
-    @source_project = new_source_project
-    @source_branch_name = new_source_branch_name
+  def initialize(new_base_project, new_base_branch_name)
+    @base_project = new_base_project
+    @base_branch_name = new_base_branch_name
   end
 
   def execute(target_project, target_branch, straight: false)
     # If compare with other project we need to fetch ref first
     target_project.repository.with_repo_branch_commit(
-      source_project.repository,
-      source_branch_name) do |commit|
+      base_project.repository,
+      base_branch_name) do |commit|
       break unless commit
 
       compare(commit.sha, target_project, target_branch, straight)
diff --git a/app/services/files/base_service.rb b/app/services/files/base_service.rb
index 80e1d1d60f2..89f7dcbaa87 100644
--- a/app/services/files/base_service.rb
+++ b/app/services/files/base_service.rb
@@ -3,8 +3,8 @@ module Files
     class ValidationError < StandardError; end
 
     def execute
-      @source_project = params[:source_project] || @project
-      @source_branch = params[:source_branch]
+      @base_project = params[:base_project] || @project
+      @base_branch = params[:base_branch]
       @target_branch = params[:target_branch]
 
       @commit_message = params[:commit_message]
@@ -22,7 +22,7 @@ module Files
       # Validate parameters
       validate
 
-      # Create new branch if it different from source_branch
+      # Create new branch if it different from base_branch
       validate_target_branch if different_branch?
 
       result = commit
@@ -38,7 +38,7 @@ module Files
     private
 
     def different_branch?
-      @source_branch != @target_branch || @source_project != @project
+      @base_branch != @target_branch || @base_project != @project
     end
 
     def file_has_changed?
@@ -59,7 +59,7 @@ module Files
       end
 
       unless project.empty_repo?
-        unless @source_project.repository.branch_exists?(@source_branch)
+        unless @base_project.repository.branch_exists?(@base_branch)
           raise_error('You can only create or edit files when you are on a branch')
         end
 
diff --git a/app/services/files/create_dir_service.rb b/app/services/files/create_dir_service.rb
index ee4e130a38f..53b6d456e0d 100644
--- a/app/services/files/create_dir_service.rb
+++ b/app/services/files/create_dir_service.rb
@@ -8,8 +8,8 @@ module Files
         branch_name: @target_branch,
         author_email: @author_email,
         author_name: @author_name,
-        source_project: @source_project,
-        source_branch_name: @source_branch)
+        base_project: @base_project,
+        base_branch_name: @base_branch)
     end
 
     def validate
diff --git a/app/services/files/create_service.rb b/app/services/files/create_service.rb
index 853c471666d..270dc6471aa 100644
--- a/app/services/files/create_service.rb
+++ b/app/services/files/create_service.rb
@@ -10,8 +10,8 @@ module Files
         update: false,
         author_email: @author_email,
         author_name: @author_name,
-        source_project: @source_project,
-        source_branch_name: @source_branch)
+        base_project: @base_project,
+        base_branch_name: @base_branch)
     end
 
     def validate
@@ -34,7 +34,7 @@ module Files
       unless project.empty_repo?
         @file_path.slice!(0) if @file_path.start_with?('/')
 
-        blob = repository.blob_at_branch(@source_branch, @file_path)
+        blob = repository.blob_at_branch(@base_branch, @file_path)
 
         if blob
           raise_error('Your changes could not be committed because a file with the same name already exists')
diff --git a/app/services/files/delete_service.rb b/app/services/files/delete_service.rb
index cfe532d49b3..d5341b9e197 100644
--- a/app/services/files/delete_service.rb
+++ b/app/services/files/delete_service.rb
@@ -8,8 +8,8 @@ module Files
         branch_name: @target_branch,
         author_email: @author_email,
         author_name: @author_name,
-        source_project: @source_project,
-        source_branch_name: @source_branch)
+        base_project: @base_project,
+        base_branch_name: @base_branch)
     end
   end
 end
diff --git a/app/services/files/multi_service.rb b/app/services/files/multi_service.rb
index f77e5d91103..ca13b887e06 100644
--- a/app/services/files/multi_service.rb
+++ b/app/services/files/multi_service.rb
@@ -10,8 +10,8 @@ module Files
         actions: params[:actions],
         author_email: @author_email,
         author_name: @author_name,
-        source_project: @source_project,
-        source_branch_name: @source_branch
+        base_project: @base_project,
+        base_branch_name: @base_branch
       )
     end
 
@@ -63,7 +63,7 @@ module Files
     end
 
     def last_commit
-      Gitlab::Git::Commit.last_for_path(repository, @source_branch, @file_path)
+      Gitlab::Git::Commit.last_for_path(repository, @base_branch, @file_path)
     end
 
     def regex_check(file)
diff --git a/app/services/files/update_service.rb b/app/services/files/update_service.rb
index 5f671817cdb..f546b169550 100644
--- a/app/services/files/update_service.rb
+++ b/app/services/files/update_service.rb
@@ -9,8 +9,8 @@ module Files
                              previous_path: @previous_path,
                              author_email: @author_email,
                              author_name: @author_name,
-                             source_project: @source_project,
-                             source_branch_name: @source_branch)
+                             base_project: @base_project,
+                             base_branch_name: @base_branch)
     end
 
     private
@@ -25,7 +25,7 @@ module Files
 
     def last_commit
       @last_commit ||= Gitlab::Git::Commit.
-        last_for_path(@source_project.repository, @source_branch, @file_path)
+        last_for_path(@base_project.repository, @base_branch, @file_path)
     end
   end
 end
diff --git a/app/services/git_operation_service.rb b/app/services/git_operation_service.rb
index 3b7f702e3ab..ec23407544c 100644
--- a/app/services/git_operation_service.rb
+++ b/app/services/git_operation_service.rb
@@ -46,23 +46,23 @@ class GitOperationService
     end
   end
 
-  # Whenever `source_branch_name` is passed, if `branch_name` doesn't exist,
-  # it would be created from `source_branch_name`.
-  # If `source_project` is passed, and the branch doesn't exist,
-  # it would try to find the source from it instead of current repository.
+  # Whenever `base_branch_name` is passed, if `branch_name` doesn't exist,
+  # it would be created from `base_branch_name`.
+  # If `base_project` is passed, and the branch doesn't exist,
+  # it would try to find the base from it instead of current repository.
   def with_branch(
     branch_name,
-    source_branch_name: nil,
-    source_project: repository.project,
+    base_branch_name: nil,
+    base_project: repository.project,
     &block)
 
     check_with_branch_arguments!(
-      branch_name, source_branch_name, source_project)
+      branch_name, base_branch_name, base_project)
 
     update_branch_with_hooks(branch_name) do
       repository.with_repo_branch_commit(
-        source_project.repository,
-        source_branch_name || branch_name,
+        base_project.repository,
+        base_branch_name || branch_name,
         &block)
     end
   end
@@ -148,27 +148,27 @@ class GitOperationService
   end
 
   def check_with_branch_arguments!(
-    branch_name, source_branch_name, source_project)
+    branch_name, base_branch_name, base_project)
     return if repository.branch_exists?(branch_name)
 
-    if repository.project != source_project
-      unless source_branch_name
+    if repository.project != base_project
+      unless base_branch_name
         raise ArgumentError,
-          'Should also pass :source_branch_name if' +
-          ' :source_project is different from current project'
+          'Should also pass :base_branch_name if' +
+          ' :base_project is different from current project'
       end
 
-      unless source_project.repository.branch_exists?(source_branch_name)
+      unless base_project.repository.branch_exists?(base_branch_name)
         raise ArgumentError,
           "Cannot find branch #{branch_name} nor" \
-          " #{source_branch_name} from" \
-          " #{source_project.path_with_namespace}"
+          " #{base_branch_name} from" \
+          " #{base_project.path_with_namespace}"
       end
-    elsif source_branch_name
-      unless repository.branch_exists?(source_branch_name)
+    elsif base_branch_name
+      unless repository.branch_exists?(base_branch_name)
         raise ArgumentError,
           "Cannot find branch #{branch_name} nor" \
-          " #{source_branch_name} from" \
+          " #{base_branch_name} from" \
           " #{repository.project.path_with_namespace}"
       end
     end