Function parsePatch

src/patch/parse.ts:16–525

(uniDiff: string)

 * information to determine them (e.g. a hunk-only patch with no file headers).
 */
export function parsePatch(uniDiff: string): StructuredPatch[] {
  const diffstr = uniDiff.split(/\n/),
        list: Partial<StructuredPatch>[] = [];
  let i = 0;

  // These helper functions identify line types that can appear between files
  // in a multi-file patch. Keeping them in one place avoids subtle
  // inconsistencies from having the same regexes duplicated in multiple places.

  // Matches `diff --git ...` lines specifically.
  function isGitDiffHeader(line: string): boolean {
    return (/^diff --git /).test(line);
  }

  // Matches lines that denote the start of a new diff's section in a
  // multi-file patch: `diff --git ...`, `Index: ...`, or `diff -r ...`.
  function isDiffHeader(line: string): boolean {
    return isGitDiffHeader(line)
        || (/^Index:\s/).test(line)
        || (/^diff(?: -r \w+)+\s/).test(line);
  }

  // Matches `--- ...` and `+++ ...` file header lines.
  function isFileHeader(line: string): boolean {
    return (/^(---|\+\+\+)\s/).test(line);
  }

  // Matches `@@ ...` hunk header lines.
  function isHunkHeader(line: string): boolean {
    return (/^@@\s/).test(line);
  }

  function parseIndex() {
    const index: Partial<StructuredPatch> = {};
    index.hunks = [];
    list.push(index);

    // Parse diff metadata
    let seenDiffHeader = false;
    while (i < diffstr.length) {
      const line = diffstr[i];

      // File header (---, +++) or hunk header (@@) found; end parsing diff metadata
      if (isFileHeader(line) || isHunkHeader(line)) {
        break;
      }

      // The next two branches handle recognized diff headers. Note that
      // isDiffHeader deliberately does NOT match arbitrary `diff`
      // commands like `diff -u -p -r1.1 -r1.2`, because in some
      // formats (e.g. CVS diffs) such lines appear as metadata within
      // a single file's header section, after an `Index:` line. See the
      // diffx documentation (https://diffx.org) for examples.
      //
      // In both branches: if we've already seen a diff header for *this*
      // file and now we encounter another one, it must belong to the
      // next file, so break.