feat: Improve diff being generated

Add `DiffCleanupSemantic` into the mix when generated diffs (PR review,
commit view and issue/comment history). This avoids trying to produce a
optimal diff and tries to reduce the amount of edits, by combing them
into larger edits, which is nicer and easier to 'look at'. There's no
need for a perfect minimal diff, as the output isn't being parsed by a
computer, it's parsed by people.

Ref: https://codeberg.org/forgejo/forgejo/issues/4996

routers/web/repo/issue_content_history.go

@@ -154,6 +154,7 @@ func GetContentHistoryDetail(ctx *context.Context) {
 	dmp := diffmatchpatch.New()
 	// `checklines=false` makes better diff result
 	diff := dmp.DiffMain(prevHistoryContentText, history.ContentText, false)
+	diff = dmp.DiffCleanupSemantic(diff)
 	diff = dmp.DiffCleanupEfficiency(diff)
 
 	// use chroma to render the diff html

services/gitdiff/highlightdiff.go

@@ -97,6 +97,7 @@ func (hcd *HighlightCodeDiff) diffWithHighlight(filename, language, codeA, codeB
 	convertedCodeB := hcd.ConvertToPlaceholders(string(highlightCodeB))
 
 	diffs := diffMatchPatch.DiffMain(convertedCodeA, convertedCodeB, true)
+	diffs = diffMatchPatch.DiffCleanupSemantic(diffs)
 	diffs = diffMatchPatch.DiffCleanupEfficiency(diffs)
 
 	for i := range diffs {