adding config value for old Bitbucket Server diff functionality

Author: mhoecke1

pr_agent/git_providers/bitbucket_server_provider.py

@@ -156,8 +156,10 @@ def get_diff_files(self) -> list[FilePatchInfo]:
         guaranteed_common_ancestor = source_commits_list[-1]['parents'][0]['id']
         destination_commits = list(self.bitbucket_client.get_commits(self.workspace_slug, self.repo_slug, guaranteed_common_ancestor, self.pr.toRef['latestCommit']))
 
-        base_sha = self.get_best_common_ancestor(source_commits_list, destination_commits, guaranteed_common_ancestor)
+        base_sha = self.pr.toRef['latestCommit']
         head_sha = self.pr.fromRef['latestCommit']
+        if "legacy_diff_calculation" not in get_settings().bitbucket_server or not get_settings().bitbucket_server.legacy_diff_calculation:
+            base_sha = self.get_best_common_ancestor(source_commits_list, destination_commits, guaranteed_common_ancestor)
 
         diff_files = []
         original_file_content_str = ""

pr_agent/settings/configuration.toml

@@ -263,6 +263,7 @@ pr_commands = [
     "/review --pr_reviewer.num_code_suggestions=0",
     "/improve --pr_code_suggestions.commitable_code_suggestions=true --pr_code_suggestions.suggestions_score_threshold=7",
 ]
+legacy_diff_calculation = true
 
 [litellm]
 # use_client = false