Merge branch '22229-use-base-sha-when-downloading-merge-requests' into 'master'

Use base SHA for patches and diffs

## What does this MR do?

Switch from using 'start SHA' to 'base SHA' for patches and diffs

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?

Makes the downloaded patches and diffs on the merge request page match the frontend-rendered "changes" in these scenarios:

* Unpatched gitlab-workhorse, downloading patchsets of open MRs (https://gitlab.com/gitlab-org/gitlab-workhorse/merge_requests/68)
* Unpatched gitlab-workhorse, downloading diffs of open and merged MRs
* Patched gitlab-workhorse, downloading patchsets of merged merge requests

## What are the relevant issue numbers?

Closes #22229

See merge request !6435

1 files changed, 6 insertions, 6 deletions

diff --git a/lib/gitlab/workhorse.rb b/lib/gitlab/workhorse.rb
index 60aae541d46..5d33f98e89e 100644
--- a/lib/gitlab/workhorse.rb
+++ b/lib/gitlab/workhorse.rb
@@ -60,7 +60,7 @@ module Gitlab
       def send_git_diff(repository, diff_refs)
         params = {
           'RepoPath'  => repository.path_to_repo,
-          'ShaFrom'   => diff_refs.start_sha,
+          'ShaFrom'   => diff_refs.base_sha,
           'ShaTo'     => diff_refs.head_sha
         }
 
@@ -73,7 +73,7 @@ module Gitlab
       def send_git_patch(repository, diff_refs)
         params = {
           'RepoPath'  => repository.path_to_repo,
-          'ShaFrom'   => diff_refs.start_sha,
+          'ShaFrom'   => diff_refs.base_sha,
           'ShaTo'     => diff_refs.head_sha
         }
 
@@ -107,15 +107,15 @@ module Gitlab
           bytes
         end
       end
-      
+
       def write_secret
         bytes = SecureRandom.random_bytes(SECRET_LENGTH)
-        File.open(secret_path, 'w:BINARY', 0600) do |f| 
+        File.open(secret_path, 'w:BINARY', 0600) do |f|
           f.chmod(0600)
           f.write(Base64.strict_encode64(bytes))
         end
       end
-      
+
       def verify_api_request!(request_headers)
         JWT.decode(
           request_headers[INTERNAL_API_REQUEST_HEADER],
@@ -128,7 +128,7 @@ module Gitlab
       def secret_path
         Rails.root.join('.gitlab_workhorse_secret')
       end
-      
+
       protected
 
       def encode(hash)