From 761061a0439f9d40e59960663d66dc6744da886e Mon Sep 17 00:00:00 2001
From: Nick Dimiduk <ndimiduk@apache.org>
Date: Mon, 11 May 2026 12:27:39 +0200
Subject: [PATCH] YETUS-1276. Add --patch-mode flag to control diff-vs-patch
 preference

YETUS-983 hardcoded dryrun_both_files to prefer cumulative .diff over
per-commit .patch. This may not work for all projects (binary handling
is a known concern), so make the preference configurable.

--patch-mode=diff (default) preserves YETUS-983 behavior.
--patch-mode=patch restores pre-YETUS-983 behavior.
The non-preferred format is always tried as fallback.
---
 precommit/src/main/shell/core.d/01-common.sh  |  4 ++
 precommit/src/main/shell/core.d/patchfiles.sh | 39 +++++++++++++------
 precommit/src/main/shell/test-patch.sh        |  1 +
 3 files changed, 33 insertions(+), 11 deletions(-)

diff --git a/precommit/src/main/shell/core.d/01-common.sh b/precommit/src/main/shell/core.d/01-common.sh
index a81668fa7..f49876fcf 100755
--- a/precommit/src/main/shell/core.d/01-common.sh
+++ b/precommit/src/main/shell/core.d/01-common.sh
@@ -201,6 +201,10 @@ function common_args
         delete_parameter "${i}"
         PATCH=${i#*=}
       ;;
+      --patch-mode=*)
+        delete_parameter "${i}"
+        PATCH_MODE=${i#*=}
+      ;;
       --patch-dir=*)
         delete_parameter "${i}"
         PATCH_DIR=${i#*=}
diff --git a/precommit/src/main/shell/core.d/patchfiles.sh b/precommit/src/main/shell/core.d/patchfiles.sh
index d8dd4d5db..6684a14b1 100755
--- a/precommit/src/main/shell/core.d/patchfiles.sh
+++ b/precommit/src/main/shell/core.d/patchfiles.sh
@@ -26,6 +26,7 @@ PATCH_METHOD=""
 PATCH_METHODS=("gitapply" "patchcmd")
 PATCH_LEVEL=0
 PATCH_HINT=""
+PATCH_MODE="diff"
 
 ## @description Use curl to download the patch as a last resort
 ## @audience    private
@@ -340,23 +341,39 @@ function patchfile_dryrun_driver
   return 1
 }
 
-## @description  dryrun both PATCH and DIFF and determine which one to use
+## @description  dryrun both PATCH and DIFF and determine which one to use.
+## @description  PATCH_MODE controls try-order: "diff" (default) avoids stale-file
+## @description  bugs from per-commit .patch stanzas (YETUS-983); "patch" restores
+## @description  the pre-YETUS-983 behavior for repos that need it.
 ## @replaceable  no
 ## @audience     private
 ## @stability    evolving
 function dryrun_both_files
 {
-  # prefer the cumulative diff: it represents the PR's net change and avoids
-  # stale-file bugs when per-commit .patch stanzas add then rename/delete files
-  # (YETUS-983). Binary files are preserved when the diff is generated locally
-  # with --binary.
-  if [[ -f "${INPUT_DIFF_FILE}" ]] && patchfile_dryrun_driver "${INPUT_DIFF_FILE}"; then
-    INPUT_APPLY_TYPE="diff"
-    INPUT_APPLIED_FILE="${INPUT_DIFF_FILE}"
+  declare first_file
+  declare first_type
+  declare second_file
+  declare second_type
+
+  if [[ "${PATCH_MODE}" == "patch" ]]; then
+    first_file="${INPUT_PATCH_FILE}"
+    first_type="patch"
+    second_file="${INPUT_DIFF_FILE}"
+    second_type="diff"
+  else
+    first_file="${INPUT_DIFF_FILE}"
+    first_type="diff"
+    second_file="${INPUT_PATCH_FILE}"
+    second_type="patch"
+  fi
+
+  if [[ -f "${first_file}" ]] && patchfile_dryrun_driver "${first_file}"; then
+    INPUT_APPLY_TYPE="${first_type}"
+    INPUT_APPLIED_FILE="${first_file}"
     return 0
-  elif [[ -f "${INPUT_PATCH_FILE}" ]] && patchfile_dryrun_driver "${INPUT_PATCH_FILE}"; then
-    INPUT_APPLY_TYPE="patch"
-    INPUT_APPLIED_FILE="${INPUT_PATCH_FILE}"
+  elif [[ -f "${second_file}" ]] && patchfile_dryrun_driver "${second_file}"; then
+    INPUT_APPLY_TYPE="${second_type}"
+    INPUT_APPLIED_FILE="${second_file}"
     return 0
   else
     return 1
diff --git a/precommit/src/main/shell/test-patch.sh b/precommit/src/main/shell/test-patch.sh
index b471ccf91..2e26f1ff7 100755
--- a/precommit/src/main/shell/test-patch.sh
+++ b/precommit/src/main/shell/test-patch.sh
@@ -675,6 +675,7 @@ function yetus_usage
   yetus_add_option "--multijdktests=<list>" "Comma delimited tests to use when multijdkdirs is used. (default: '${jdktlist}')"
   yetus_add_option "--offline" "Avoid connecting to the network"
   yetus_add_option "--patch-dir=<dir>" "The directory for working and output files (default '/tmp/test-patch-${PROJECT_NAME}/pid')"
+  yetus_add_option "--patch-mode=<diff|patch>" "Try cumulative diff or per-commit patch first (default: '${PATCH_MODE}')"
   yetus_add_option "--personality=<file>" "The personality file to load"
   yetus_add_option "--plugins=<list>" "Specify which plug-ins to add/delete (comma delimited; use 'all' for all found) e.g. --plugins=all,-ant,-scalac (all plugins except ant and scalac)"
   yetus_add_option "--proclimit=<num>" "Limit on the number of processes (default: ${PROC_LIMIT})"