Fix incorrect comment diff hunk parsing, fix github asset ID nil panic (#35046)

* Fix missing the first char when parsing diff hunk header
* Fix #35040
* Fix #35049

----

Introduced in
https://github.com/go-gitea/gitea/pull/12047/files#diff-de48c2f70e24ff5603180acf8b5ce9d0356ede8a45bfbf2a485707282ace6d6aR268

Before:

<img width="487" height="167" alt="image"
src="https://github.com/user-attachments/assets/17524c76-a296-4b4b-a4f9-c5150c41bae5"
/>

After:

<img width="749" height="144" alt="image"
src="https://github.com/user-attachments/assets/bcb12c76-c1ae-40f1-81b7-183d15f891db"
/>

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

3 files changed, 26 insertions, 11 deletions

diff --git a/modules/git/diff.go b/modules/git/diff.go
index c4df6b8063..35d115be0e 100644
--- a/modules/git/diff.go
+++ b/modules/git/diff.go
@@ -99,9 +99,9 @@ func GetRepoRawDiffForFile(repo *Repository, startCommit, endCommit string, diff
 	return nil
 }
 
-// ParseDiffHunkString parse the diffhunk content and return
-func ParseDiffHunkString(diffhunk string) (leftLine, leftHunk, rightLine, righHunk int) {
-	ss := strings.Split(diffhunk, "@@")
+// ParseDiffHunkString parse the diff hunk content and return
+func ParseDiffHunkString(diffHunk string) (leftLine, leftHunk, rightLine, rightHunk int) {
+	ss := strings.Split(diffHunk, "@@")
 	ranges := strings.Split(ss[1][1:], " ")
 	leftRange := strings.Split(ranges[0], ",")
 	leftLine, _ = strconv.Atoi(leftRange[0][1:])
@@ -112,14 +112,19 @@ func ParseDiffHunkString(diffhunk string) (leftLine, leftHunk, rightLine, righHu
 		rightRange := strings.Split(ranges[1], ",")
 		rightLine, _ = strconv.Atoi(rightRange[0])
 		if len(rightRange) > 1 {
-			righHunk, _ = strconv.Atoi(rightRange[1])
+			rightHunk, _ = strconv.Atoi(rightRange[1])
 		}
 	} else {
-		log.Debug("Parse line number failed: %v", diffhunk)
+		log.Debug("Parse line number failed: %v", diffHunk)
 		rightLine = leftLine
-		righHunk = leftHunk
+		rightHunk = leftHunk
 	}
-	return leftLine, leftHunk, rightLine, righHunk
+	if rightLine == 0 {
+		// FIXME: GIT-DIFF-CUT-BUG search this tag to see details
+		// this is only a hacky patch, the rightLine&rightHunk might still be incorrect in some cases.
+		rightLine++
+	}
+	return leftLine, leftHunk, rightLine, rightHunk
 }
 
 // Example: @@ -1,8 +1,9 @@ => [..., 1, 8, 1, 9]
@@ -270,6 +275,12 @@ func CutDiffAroundLine(originalDiff io.Reader, line int64, old bool, numbersOfLi
 			oldNumOfLines++
 		}
 	}
+
+	// "git diff" outputs "@@ -1 +1,3 @@" for "OLD" => "A\nB\nC"
+	// FIXME: GIT-DIFF-CUT-BUG But there is a bug in CutDiffAroundLine, then the "Patch" stored in the comment model becomes "@@ -1,1 +0,4 @@"
+	// It may generate incorrect results for difference cases, for example: delete 2 line add 1 line, delete 2 line add 2 line etc, need to double check.
+	// For example: "L1\nL2" => "A\nB", then the patch shows "L2" as line 1 on the left (deleted part)
+
 	// construct the new hunk header
 	newHunk[headerLines] = fmt.Sprintf("@@ -%d,%d +%d,%d @@",
 		oldBegin, oldNumOfLines, newBegin, newNumOfLines)
diff --git a/services/gitdiff/gitdiff.go b/services/gitdiff/gitdiff.go
index 9964329876..0b6e6be82b 100644
--- a/services/gitdiff/gitdiff.go
+++ b/services/gitdiff/gitdiff.go
@@ -179,7 +179,7 @@ func (d *DiffLine) GetExpandDirection() DiffLineExpandDirection {
 }
 
 func getDiffLineSectionInfo(treePath, line string, lastLeftIdx, lastRightIdx int) *DiffLineSectionInfo {
-	leftLine, leftHunk, rightLine, righHunk := git.ParseDiffHunkString(line)
+	leftLine, leftHunk, rightLine, rightHunk := git.ParseDiffHunkString(line)
 
 	return &DiffLineSectionInfo{
 		Path:          treePath,
@@ -188,7 +188,7 @@ func getDiffLineSectionInfo(treePath, line string, lastLeftIdx, lastRightIdx int
 		LeftIdx:       leftLine,
 		RightIdx:      rightLine,
 		LeftHunkSize:  leftHunk,
-		RightHunkSize: righHunk,
+		RightHunkSize: rightHunk,
 	}
 }
 
@@ -290,7 +290,7 @@ func (diffSection *DiffSection) GetComputedInlineDiffFor(diffLine *DiffLine, loc
 	// try to find equivalent diff line. ignore, otherwise
 	switch diffLine.Type {
 	case DiffLineSection:
-		return getLineContent(diffLine.Content[1:], locale)
+		return getLineContent(diffLine.Content, locale)
 	case DiffLineAdd:
 		compareDiffLine := diffSection.GetLine(diffLine.Match)
 		return diffSection.getDiffLineForRender(DiffLineAdd, compareDiffLine, diffLine, locale)
@@ -856,6 +856,7 @@ func parseHunks(ctx context.Context, curFile *DiffFile, maxLines, maxLineCharact
 			lastLeftIdx = -1
 			curFile.Sections = append(curFile.Sections, curSection)
 
+			// FIXME: the "-1" can't be right, these "line idx" are all 1-based, maybe there are other bugs that covers this bug.
 			lineSectionInfo := getDiffLineSectionInfo(curFile.Name, line, leftLine-1, rightLine-1)
 			diffLine := &DiffLine{
 				Type:        DiffLineSection,
diff --git a/services/migrations/github.go b/services/migrations/github.go
index 2ce11615c6..c6cd6ea173 100644
--- a/services/migrations/github.go
+++ b/services/migrations/github.go
@@ -322,7 +322,10 @@ func (g *GithubDownloaderV3) convertGithubRelease(ctx context.Context, rel *gith
 	httpClient := NewMigrationHTTPClient()
 
 	for _, asset := range rel.Assets {
-		assetID := *asset.ID // Don't optimize this, for closure we need a local variable
+		assetID := asset.GetID() // Don't optimize this, for closure we need a local variable TODO: no need to do so in new Golang
+		if assetID == 0 {
+			continue
+		}
 		r.Assets = append(r.Assets, &base.ReleaseAsset{
 			ID:            asset.GetID(),
 			Name:          asset.GetName(),