Function formatPatchHeader

app/src/lib/patch-formatter.ts:22–36

* Generates a string matching the format of a GNU unified diff header excluding * the (optional) timestamp fields * * Note that this multi-line string includes a trailing newline. * * @param from The relative path to the original version of the file or * null if the file is newly

(from: string | null, to: string | null)

 *              null if the file is the file is newly created.
 */
function formatPatchHeader(from: string | null, to: string | null): string {
  // https://en.wikipedia.org/wiki/Diff_utility
  //
  // > At the beginning of the patch is the file information, including the full
  // > path and a time stamp delimited by a tab character.
  // >
  // > [...] the original file is preceded by "---" and the new file is preceded
  // > by "+++".
  //
  // We skip the time stamp to match git
  const fromPath = from ? `a/${from}` : '/dev/null'
  const toPath = to ? `b/${to}` : '/dev/null'

  return `--- ${fromPath}\n+++ ${toPath}\n`
}

/**
 * Generates a string matching the format of a GNU unified diff header excluding