Decouple diff stats query from actual diffing (#33810)

The diff stats are no longer part of the diff generation.
Use `GetDiffShortStat` instead to get the total number of changed files,
added lines, and deleted lines.
As such, `gitdiff.GetDiff` can be simplified:
It should not do more than expected.

And do not run "git diff --shortstat" for pull list. Fix #31492

modules/git/repo_compare.go

@@ -174,17 +174,9 @@ func (repo *Repository) GetDiffNumChangedFiles(base, head string, directComparis
 	return w.numLines, nil
 }
 
-// GetDiffShortStat counts number of changed files, number of additions and deletions
-func (repo *Repository) GetDiffShortStat(base, head string) (numFiles, totalAdditions, totalDeletions int, err error) {
-	numFiles, totalAdditions, totalDeletions, err = GetDiffShortStat(repo.Ctx, repo.Path, nil, base+"..."+head)
-	if err != nil && strings.Contains(err.Error(), "no merge base") {
-		return GetDiffShortStat(repo.Ctx, repo.Path, nil, base, head)
-	}
-	return numFiles, totalAdditions, totalDeletions, err
-}
-
-// GetDiffShortStat counts number of changed files, number of additions and deletions
-func GetDiffShortStat(ctx context.Context, repoPath string, trustedArgs TrustedCmdArgs, dynamicArgs ...string) (numFiles, totalAdditions, totalDeletions int, err error) {
+// GetDiffShortStatByCmdArgs counts number of changed files, number of additions and deletions
+// TODO: it can be merged with another "GetDiffShortStat" in the future
+func GetDiffShortStatByCmdArgs(ctx context.Context, repoPath string, trustedArgs TrustedCmdArgs, dynamicArgs ...string) (numFiles, totalAdditions, totalDeletions int, err error) {
 	// Now if we call:
 	// $ git diff --shortstat 1ebb35b98889ff77299f24d82da426b434b0cca0...788b8b1440462d477f45b0088875
 	// we get:

modules/structs/pull.go

@@ -25,11 +25,13 @@ type PullRequest struct {
 	Draft                   bool       `json:"draft"`
 	IsLocked                bool       `json:"is_locked"`
 	Comments                int        `json:"comments"`
+
 	// number of review comments made on the diff of a PR review (not including comments on commits or issues in a PR)
-	ReviewComments int `json:"review_comments"`
-	Additions      int `json:"additions"`
-	Deletions      int `json:"deletions"`
-	ChangedFiles   int `json:"changed_files"`
+	ReviewComments int `json:"review_comments,omitempty"`
+
+	Additions    *int `json:"additions,omitempty"`
+	Deletions    *int `json:"deletions,omitempty"`
+	ChangedFiles *int `json:"changed_files,omitempty"`
 
 	HTMLURL  string `json:"html_url"`
 	DiffURL  string `json:"diff_url"`

routers/api/v1/repo/pull.go

@@ -1591,6 +1591,7 @@ func GetPullRequestFiles(ctx *context.APIContext) {
 	maxLines := setting.Git.MaxGitDiffLines
 
 	// FIXME: If there are too many files in the repo, may cause some unpredictable issues.
+	// FIXME: it doesn't need to call "GetDiff" to do various parsing and highlighting
 	diff, err := gitdiff.GetDiff(ctx, baseGitRepo,
 		&gitdiff.DiffOptions{
 			BeforeCommitID:     startCommitID,
@@ -1606,9 +1607,14 @@ func GetPullRequestFiles(ctx *context.APIContext) {
 		return
 	}
 
+	diffShortStat, err := gitdiff.GetDiffShortStat(baseGitRepo, startCommitID, endCommitID)
+	if err != nil {
+		ctx.APIErrorInternal(err)
+		return
+	}
 	listOptions := utils.GetListOptions(ctx)
 
-	totalNumberOfFiles := diff.NumFiles
+	totalNumberOfFiles := diffShortStat.NumFiles
 	totalNumberOfPages := int(math.Ceil(float64(totalNumberOfFiles) / float64(listOptions.PageSize)))
 
 	start, limit := listOptions.GetSkipTake()

routers/web/repo/commit.go

@@ -321,12 +321,17 @@ func Diff(ctx *context.Context) {
 		MaxLineCharacters:  setting.Git.MaxGitDiffLineCharacters,
 		MaxFiles:           maxFiles,
 		WhitespaceBehavior: gitdiff.GetWhitespaceFlag(ctx.Data["WhitespaceBehavior"].(string)),
-		FileOnly:           fileOnly,
 	}, files...)
 	if err != nil {
 		ctx.NotFound(err)
 		return
 	}
+	diffShortStat, err := gitdiff.GetDiffShortStat(gitRepo, "", commitID)
+	if err != nil {
+		ctx.ServerError("GetDiffShortStat", err)
+		return
+	}
+	ctx.Data["DiffShortStat"] = diffShortStat
 
 	parents := make([]string, commit.ParentCount())
 	for i := 0; i < commit.ParentCount(); i++ {
@@ -383,7 +388,7 @@ func Diff(ctx *context.Context) {
 	ctx.Data["Verification"] = verification
 	ctx.Data["Author"] = user_model.ValidateCommitWithEmail(ctx, commit)
 	ctx.Data["Parents"] = parents
-	ctx.Data["DiffNotAvailable"] = diff.NumFiles == 0
+	ctx.Data["DiffNotAvailable"] = diffShortStat.NumFiles == 0
 
 	if err := asymkey_model.CalculateTrustStatus(verification, ctx.Repo.Repository.GetTrustModel(), func(user *user_model.User) (bool, error) {
 		return repo_model.IsOwnerMemberCollaborator(ctx, ctx.Repo.Repository, user.ID)

routers/web/repo/compare.go

@@ -624,14 +624,19 @@ func PrepareCompareDiff(
 			MaxFiles:           maxFiles,
 			WhitespaceBehavior: whitespaceBehavior,
 			DirectComparison:   ci.DirectComparison,
-			FileOnly:           fileOnly,
 		}, ctx.FormStrings("files")...)
 	if err != nil {
-		ctx.ServerError("GetDiffRangeWithWhitespaceBehavior", err)
+		ctx.ServerError("GetDiff", err)
 		return false
 	}
+	diffShortStat, err := gitdiff.GetDiffShortStat(ci.HeadGitRepo, beforeCommitID, headCommitID)
+	if err != nil {
+		ctx.ServerError("GetDiffShortStat", err)
+		return false
+	}
+	ctx.Data["DiffShortStat"] = diffShortStat
 	ctx.Data["Diff"] = diff
-	ctx.Data["DiffNotAvailable"] = diff.NumFiles == 0
+	ctx.Data["DiffNotAvailable"] = diffShortStat.NumFiles == 0
 
 	if !fileOnly {
 		diffTree, err := gitdiff.GetDiffTree(ctx, ci.HeadGitRepo, false, beforeCommitID, headCommitID)

routers/web/repo/editor.go

@@ -423,7 +423,7 @@ func DiffPreviewPost(ctx *context.Context) {
 		return
 	}
 
-	if diff.NumFiles != 0 {
+	if len(diff.Files) != 0 {
 		ctx.Data["File"] = diff.Files[0]
 	}
 

routers/web/repo/pull.go

@@ -200,22 +200,13 @@ func GetPullDiffStats(ctx *context.Context) {
 		return
 	}
 
-	diffOptions := &gitdiff.DiffOptions{
-		BeforeCommitID:     mergeBaseCommitID,
-		AfterCommitID:      headCommitID,
-		MaxLines:           setting.Git.MaxGitDiffLines,
-		MaxLineCharacters:  setting.Git.MaxGitDiffLineCharacters,
-		MaxFiles:           setting.Git.MaxGitDiffFiles,
-		WhitespaceBehavior: gitdiff.GetWhitespaceFlag(ctx.Data["WhitespaceBehavior"].(string)),
-	}
-
-	diff, err := gitdiff.GetPullDiffStats(ctx.Repo.GitRepo, diffOptions)
+	diffShortStat, err := gitdiff.GetDiffShortStat(ctx.Repo.GitRepo, mergeBaseCommitID, headCommitID)
 	if err != nil {
-		ctx.ServerError("GetPullDiffStats", err)
+		ctx.ServerError("GetDiffShortStat", err)
 		return
 	}
 
-	ctx.Data["Diff"] = diff
+	ctx.Data["DiffShortStat"] = diffShortStat
 }
 
 func GetMergedBaseCommitID(ctx *context.Context, issue *issues_model.Issue) string {
@@ -752,36 +743,43 @@ func viewPullFiles(ctx *context.Context, specifiedStartCommit, specifiedEndCommi
 		MaxLineCharacters:  setting.Git.MaxGitDiffLineCharacters,
 		MaxFiles:           maxFiles,
 		WhitespaceBehavior: gitdiff.GetWhitespaceFlag(ctx.Data["WhitespaceBehavior"].(string)),
-		FileOnly:           fileOnly,
 	}
 
 	if !willShowSpecifiedCommit {
 		diffOptions.BeforeCommitID = startCommitID
 	}
 
-	var methodWithError string
-	var diff *gitdiff.Diff
-	shouldGetUserSpecificDiff := false
+	diff, err := gitdiff.GetDiff(ctx, gitRepo, diffOptions, files...)
+	if err != nil {
+		ctx.ServerError("GetDiff", err)
+		return
+	}
 
 	// if we're not logged in or only a single commit (or commit range) is shown we
 	// have to load only the diff and not get the viewed information
 	// as the viewed information is designed to be loaded only on latest PR
 	// diff and if you're signed in.
+	shouldGetUserSpecificDiff := false
 	if !ctx.IsSigned || willShowSpecifiedCommit || willShowSpecifiedCommitRange {
-		diff, err = gitdiff.GetDiff(ctx, gitRepo, diffOptions, files...)
-		methodWithError = "GetDiff"
+		// do nothing
 	} else {
-		diff, err = gitdiff.SyncAndGetUserSpecificDiff(ctx, ctx.Doer.ID, pull, gitRepo, diffOptions, files...)
-		methodWithError = "SyncAndGetUserSpecificDiff"
 		shouldGetUserSpecificDiff = true
+		err = gitdiff.SyncUserSpecificDiff(ctx, ctx.Doer.ID, pull, gitRepo, diff, diffOptions, files...)
+		if err != nil {
+			ctx.ServerError("SyncUserSpecificDiff", err)
+			return
+		}
 	}
+
+	diffShortStat, err := gitdiff.GetDiffShortStat(ctx.Repo.GitRepo, startCommitID, endCommitID)
 	if err != nil {
-		ctx.ServerError(methodWithError, err)
+		ctx.ServerError("GetDiffShortStat", err)
 		return
 	}
+	ctx.Data["DiffShortStat"] = diffShortStat
 
 	ctx.PageData["prReview"] = map[string]any{
-		"numberOfFiles":       diff.NumFiles,
+		"numberOfFiles":       diffShortStat.NumFiles,
 		"numberOfViewedFiles": diff.NumViewedFiles,
 	}
 
@@ -840,7 +838,7 @@ func viewPullFiles(ctx *context.Context, specifiedStartCommit, specifiedEndCommi
 	}
 
 	ctx.Data["Diff"] = diff
-	ctx.Data["DiffNotAvailable"] = diff.NumFiles == 0
+	ctx.Data["DiffNotAvailable"] = diffShortStat.NumFiles == 0
 
 	baseCommit, err := ctx.Repo.GitRepo.GetCommit(startCommitID)
 	if err != nil {

services/convert/git_commit.go

@@ -210,17 +210,15 @@ func ToCommit(ctx context.Context, repo *repo_model.Repository, gitRepo *git.Rep
 
 	// Get diff stats for commit
 	if opts.Stat {
-		diff, err := gitdiff.GetDiff(ctx, gitRepo, &gitdiff.DiffOptions{
-			AfterCommitID: commit.ID.String(),
-		})
+		diffShortStat, err := gitdiff.GetDiffShortStat(gitRepo, "", commit.ID.String())
 		if err != nil {
 			return nil, err
 		}
 
 		res.Stats = &api.CommitStats{
-			Total:     diff.TotalAddition + diff.TotalDeletion,
-			Additions: diff.TotalAddition,
-			Deletions: diff.TotalDeletion,
+			Total:     diffShortStat.TotalAddition + diffShortStat.TotalDeletion,
+			Additions: diffShortStat.TotalAddition,
+			Deletions: diffShortStat.TotalDeletion,
 		}
 	}
 

services/convert/pull.go

@@ -17,8 +17,10 @@ import (
 	"code.gitea.io/gitea/modules/git"
 	"code.gitea.io/gitea/modules/gitrepo"
 	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/setting"
 	api "code.gitea.io/gitea/modules/structs"
 	"code.gitea.io/gitea/modules/util"
+	"code.gitea.io/gitea/services/gitdiff"
 )
 
 // ToAPIPullRequest assumes following fields have been assigned with valid values:
@@ -239,9 +241,13 @@ func ToAPIPullRequest(ctx context.Context, pr *issues_model.PullRequest, doer *u
 		// Calculate diff
 		startCommitID = pr.MergeBase
 
-		apiPullRequest.ChangedFiles, apiPullRequest.Additions, apiPullRequest.Deletions, err = gitRepo.GetDiffShortStat(startCommitID, endCommitID)
+		diffShortStats, err := gitdiff.GetDiffShortStat(gitRepo, startCommitID, endCommitID)
 		if err != nil {
 			log.Error("GetDiffShortStat: %v", err)
+		} else {
+			apiPullRequest.ChangedFiles = &diffShortStats.NumFiles
+			apiPullRequest.Additions = &diffShortStats.TotalAddition
+			apiPullRequest.Deletions = &diffShortStats.TotalDeletion
 		}
 	}
 
@@ -462,12 +468,6 @@ func ToAPIPullRequests(ctx context.Context, baseRepo *repo_model.Repository, prs
 				return nil, err
 			}
 
-			// Outer scope variables to be used in diff calculation
-			var (
-				startCommitID string
-				endCommitID   string
-			)
-
 			if git.IsErrBranchNotExist(err) {
 				headCommitID, err := headGitRepo.GetRefCommitID(apiPullRequest.Head.Ref)
 				if err != nil && !git.IsErrNotExist(err) {
@@ -476,7 +476,6 @@ func ToAPIPullRequests(ctx context.Context, baseRepo *repo_model.Repository, prs
 				}
 				if err == nil {
 					apiPullRequest.Head.Sha = headCommitID
-					endCommitID = headCommitID
 				}
 			} else {
 				commit, err := headBranch.GetCommit()
@@ -487,17 +486,8 @@ func ToAPIPullRequests(ctx context.Context, baseRepo *repo_model.Repository, prs
 				if err == nil {
 					apiPullRequest.Head.Ref = pr.HeadBranch
 					apiPullRequest.Head.Sha = commit.ID.String()
-					endCommitID = commit.ID.String()
 				}
 			}
-
-			// Calculate diff
-			startCommitID = pr.MergeBase
-
-			apiPullRequest.ChangedFiles, apiPullRequest.Additions, apiPullRequest.Deletions, err = gitRepo.GetDiffShortStat(startCommitID, endCommitID)
-			if err != nil {
-				log.Error("GetDiffShortStat: %v", err)
-			}
 		}
 
 		if len(apiPullRequest.Head.Sha) == 0 && len(apiPullRequest.Head.Ref) != 0 {
@@ -518,6 +508,12 @@ func ToAPIPullRequests(ctx context.Context, baseRepo *repo_model.Repository, prs
 			apiPullRequest.MergedBy = ToUser(ctx, pr.Merger, nil)
 		}
 
+		// Do not provide "ChangeFiles/Additions/Deletions" for the PR list, because the "diff" is quite slow
+		// If callers are interested in these values, they should do a separate request to get the PR details
+		if apiPullRequest.ChangedFiles != nil || apiPullRequest.Additions != nil || apiPullRequest.Deletions != nil {
+			setting.PanicInDevOrTesting("ChangedFiles/Additions/Deletions should not be set in PR list")
+		}
+
 		apiPullRequests = append(apiPullRequests, apiPullRequest)
 	}