Share and unify limit for intra line diffs

Closes #13838

app/src/ui/diff/diff-helpers.tsx

@@ -387,3 +387,9 @@ export function getLargestLineNumber(hunks: DiffHunk[]): number {
 export function getNumberOfDigits(val: number): number {
   return (Math.log(val) * Math.LOG10E + 1) | 0
 }
+
+/**
+ * The longest line for which we'd try to calculate a line diff, this matches
+ * GitHub.com's behavior.
+ **/
+export const MaxIntraLineDiffStringLength = 1024

app/src/ui/diff/side-by-side-diff.tsx

@@ -45,6 +45,7 @@ import {
   DiffColumn,
   getLineWidthFromDigitCount,
   getNumberOfDigits,
+  MaxIntraLineDiffStringLength,
 } from './diff-helpers'
 import { showContextualMenu } from '../main-process-proxy'
 import { getTokens } from './diff-syntax-mode'
@@ -59,7 +60,6 @@ import { IMenuItem } from '../../lib/menu-item'
 import { HiddenBidiCharsWarning } from './hidden-bidi-chars-warning'
 
 const DefaultRowHeight = 20
-const MaxLineLengthToCalculateDiff = 240
 
 export interface ISelectionPoint {
   readonly column: DiffColumn
@@ -1164,8 +1164,8 @@ function getModifiedRows(
       const deletedLine = deletedLines[i]
 
       if (
-        addedLine.line.content.length < MaxLineLengthToCalculateDiff &&
-        deletedLine.line.content.length < MaxLineLengthToCalculateDiff
+        addedLine.line.content.length < MaxIntraLineDiffStringLength &&
+        deletedLine.line.content.length < MaxIntraLineDiffStringLength
       ) {
         const { before, after } = getDiffTokens(
           deletedLine.line.content,

app/src/ui/diff/text-diff.tsx

@@ -46,6 +46,7 @@ import {
   canSelect,
   getLineWidthFromDigitCount,
   getNumberOfDigits,
+  MaxIntraLineDiffStringLength,
 } from './diff-helpers'
 import {
   expandTextDiffHunk,
@@ -58,9 +59,6 @@ import { WhitespaceHintPopover } from './whitespace-hint-popover'
 import { PopoverCaretPosition } from '../lib/popover'
 import { HiddenBidiCharsWarning } from './hidden-bidi-chars-warning'
 
-/** The longest line for which we'd try to calculate a line diff. */
-const MaxIntraLineDiffStringLength = 4096
-
 // This is a custom version of the no-newline octicon that's exactly as
 // tall as it needs to be (8px) which helps with aligning it on the line.
 export const narrowNoNewlineSymbol = {