Add setting to disable the git apply step in test patch (#22130)

custom/conf/app.example.ini

@@ -996,6 +996,9 @@ ROUTER = console
 ;;
 ;; Add co-authored-by and co-committed-by trailers if committer does not match author
 ;ADD_CO_COMMITTER_TRAILERS = true
+;;
+;; In addition to testing patches using the three-way merge method, re-test conflicting patches with git apply
+;TEST_CONFLICTING_PATCHES_WITH_GIT_APPLY = true
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

docs/content/doc/advanced/config-cheat-sheet.en-us.md

@@ -101,6 +101,7 @@ Values containing `#` or `;` must be quoted using `` ` `` or `"""`.
 - `DEFAULT_MERGE_MESSAGE_OFFICIAL_APPROVERS_ONLY`: **true**: In default merge messages only include approvers who are officially allowed to review.
 - `POPULATE_SQUASH_COMMENT_WITH_COMMIT_MESSAGES`: **false**: In default squash-merge messages include the commit message of all commits comprising the pull request.
 - `ADD_CO_COMMITTER_TRAILERS`: **true**: Add co-authored-by and co-committed-by trailers to merge commit messages if committer does not match author.
+- `TEST_CONFLICTING_PATCHES_WITH_GIT_APPLY`: **true**: PR patches are tested using a three-way merge method to discover if there are conflicts. If this setting is set to **true**, conflicting patches will be retested using `git apply` - This was the previous behaviour in 1.18 (and earlier) but is somewhat inefficient. Please report if you find that this setting is required.
 
 ### Repository - Issue (`repository.issue`)
 

modules/setting/repository.go

@@ -83,6 +83,7 @@ var (
 			DefaultMergeMessageOfficialApproversOnly bool
 			PopulateSquashCommentWithCommitMessages  bool
 			AddCoCommitterTrailers                   bool
+			TestConflictingPatchesWithGitApply       bool
 		} `ini:"repository.pull-request"`
 
 		// Issue Setting
@@ -205,6 +206,7 @@ var (
 			DefaultMergeMessageOfficialApproversOnly bool
 			PopulateSquashCommentWithCommitMessages  bool
 			AddCoCommitterTrailers                   bool
+			TestConflictingPatchesWithGitApply       bool
 		}{
 			WorkInProgressPrefixes: []string{"WIP:", "[WIP]"},
 			// Same as GitHub. See
@@ -219,6 +221,7 @@ var (
 			DefaultMergeMessageOfficialApproversOnly: true,
 			PopulateSquashCommentWithCommitMessages:  false,
 			AddCoCommitterTrailers:                   true,
+			TestConflictingPatchesWithGitApply:       true,
 		},
 
 		// Issue settings

services/pull/patch.go

@@ -23,6 +23,7 @@ import (
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/process"
 	repo_module "code.gitea.io/gitea/modules/repository"
+	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/util"
 
 	"github.com/gobwas/glob"
@@ -289,13 +290,15 @@ func checkConflicts(ctx context.Context, pr *issues_model.PullRequest, gitRepo *
 
 	// 2. AttemptThreeWayMerge first - this is much quicker than plain patch to base
 	description := fmt.Sprintf("PR[%d] %s/%s#%d", pr.ID, pr.BaseRepo.OwnerName, pr.BaseRepo.Name, pr.Index)
-	conflict, _, err := AttemptThreeWayMerge(ctx,
+	conflict, conflictFiles, err := AttemptThreeWayMerge(ctx,
 		tmpBasePath, gitRepo, pr.MergeBase, "base", "tracking", description)
 	if err != nil {
 		return false, err
 	}
 
 	if !conflict {
+		// No conflicts detected so we need to check if the patch is empty...
+		// a. Write the newly merged tree and check the new tree-hash
 		var treeHash string
 		treeHash, _, err = git.NewCommand(ctx, "write-tree").RunStdString(&git.RunOpts{Dir: tmpBasePath})
 		if err != nil {
@@ -307,6 +310,8 @@ func checkConflicts(ctx context.Context, pr *issues_model.PullRequest, gitRepo *
 		if err != nil {
 			return false, err
 		}
+
+		// b. compare the new tree-hash with the base tree hash
 		if treeHash == baseTree.ID.String() {
 			log.Debug("PullRequest[%d]: Patch is empty - ignoring", pr.ID)
 			pr.Status = issues_model.PullRequestStatusEmpty
@@ -315,9 +320,17 @@ func checkConflicts(ctx context.Context, pr *issues_model.PullRequest, gitRepo *
 		return false, nil
 	}
 
-	// 3. OK read-tree has failed so we need to try a different thing - this might actually succeed where the above fails due to whitespace handling.
+	// 3. OK the three-way merge method has detected conflicts
+	// 3a. Are still testing with GitApply? If not set the conflict status and move on
+	if !setting.Repository.PullRequest.TestConflictingPatchesWithGitApply {
+		pr.Status = issues_model.PullRequestStatusConflict
+		pr.ConflictedFiles = conflictFiles
+
+		log.Trace("Found %d files conflicted: %v", len(pr.ConflictedFiles), pr.ConflictedFiles)
+		return true, nil
+	}
 
-	// 3a. Create a plain patch from head to base
+	// 3b. Create a plain patch from head to base
 	tmpPatchFile, err := os.CreateTemp("", "patch")
 	if err != nil {
 		log.Error("Unable to create temporary patch file! Error: %v", err)
@@ -340,8 +353,9 @@ func checkConflicts(ctx context.Context, pr *issues_model.PullRequest, gitRepo *
 	patchPath := tmpPatchFile.Name()
 	tmpPatchFile.Close()
 
-	// 3b. if the size of that patch is 0 - there can be no conflicts!
+	// 3c. if the size of that patch is 0 - there can be no conflicts!
 	if stat.Size() == 0 {
+		log.Critical("git-apply--check patch checker found empty PR when read-tree found conflicts in PR#%d[%d] in %#-v", pr.Index, pr.ID, pr.BaseRepo)
 		log.Debug("PullRequest[%d]: Patch is empty - ignoring", pr.ID)
 		pr.Status = issues_model.PullRequestStatusEmpty
 		return false, nil
@@ -472,6 +486,8 @@ func checkConflicts(ctx context.Context, pr *issues_model.PullRequest, gitRepo *
 	} else if err != nil {
 		return false, fmt.Errorf("git apply --check: %w", err)
 	}
+
+	log.Critical("git-apply--check patch checker found no conflicts when read-tree found conflicts in PR#%d[%d] in %#-v", pr.Index, pr.ID, pr.BaseRepo)
 	return false, nil
 }