Function formatPatch

app/src/lib/patch-formatter.ts:129–232

(
  file: WorkingDirectoryFileChange,
  diff: ITextDiff | ILargeTextDiff
)

 * @param diff  The source diff
 */
export function formatPatch(
  file: WorkingDirectoryFileChange,
  diff: ITextDiff | ILargeTextDiff
): string {
  let patch = ''

  diff.hunks.forEach((hunk, hunkIndex) => {
    let hunkBuf = ''

    let oldCount = 0
    let newCount = 0

    let anyAdditionsOrDeletions = false

    hunk.lines.forEach((line, lineIndex) => {
      const absoluteIndex = hunk.unifiedDiffStart + lineIndex

      // We write our own hunk headers
      if (line.type === DiffLineType.Hunk) {
        return
      }

      // Context lines can always be let through, they will
      // never appear for new files.
      if (line.type === DiffLineType.Context) {
        hunkBuf += `${line.text}\n`
        oldCount++
        newCount++
      } else if (file.selection.isSelected(absoluteIndex)) {
        // A line selected for inclusion.

        // Use the line as-is
        hunkBuf += `${line.text}\n`

        if (line.type === DiffLineType.Add) {
          newCount++
        }
        if (line.type === DiffLineType.Delete) {
          oldCount++
        }

        anyAdditionsOrDeletions = true
      } else {
        // Unselected lines in new files needs to be ignored. A new file by
        // definition only consists of additions and therefore so will the
        // partial patch. If the user has elected not to commit a particular
        // addition we need to generate a patch that pretends that the line
        // never existed.
        if (
          file.status.kind === AppFileStatusKind.New ||
          file.status.kind === AppFileStatusKind.Untracked
        ) {
          return
        }

        // An unselected added line has no impact on this patch, pretend
        // it was never added to the old file by dropping it.
        if (line.type === DiffLineType.Add) {