Function unifiedFilePatch

src/apply-patch.ts:412–465

(
  oldPath: string,
  newPath: string,
  oldContent: string | null,
  newContent: string | null,
)

}

function unifiedFilePatch(
  oldPath: string,
  newPath: string,
  oldContent: string | null,
  newContent: string | null,
): string {
  const oldLines = fileLines(oldContent ?? "");
  const newLines = fileLines(newContent ?? "");
  let prefix = 0;
  while (
    prefix < oldLines.length &&
    prefix < newLines.length &&
    oldLines[prefix] === newLines[prefix]
  ) {
    prefix += 1;
  }

  let suffix = 0;
  while (
    suffix < oldLines.length - prefix &&
    suffix < newLines.length - prefix &&
    oldLines[oldLines.length - 1 - suffix] === newLines[newLines.length - 1 - suffix]
  ) {
    suffix += 1;
  }

  const contextBefore = Math.min(3, prefix);
  const contextAfter = Math.min(3, suffix);
  const oldChanged = oldLines.slice(prefix, oldLines.length - suffix);
  const newChanged = newLines.slice(prefix, newLines.length - suffix);
  const before = oldLines.slice(prefix - contextBefore, prefix);
  const after = oldLines.slice(oldLines.length - suffix, oldLines.length - suffix + contextAfter);
  const oldCount = contextBefore + oldChanged.length + contextAfter;
  const newCount = contextBefore + newChanged.length + contextAfter;
  const oldStart = oldContent === null ? 0 : prefix - contextBefore + 1;
  const newStart = newContent === null ? 0 : prefix - contextBefore + 1;
  const displayOld = oldContent === null ? "/dev/null" : `a/${oldPath}`;
  const displayNew = newContent === null ? "/dev/null" : `b/${newPath}`;

  return [
    `diff --git a/${oldPath} b/${newPath}`,
    oldContent === null ? "new file mode 100644" : undefined,
    newContent === null ? "deleted file mode 100644" : undefined,
    `--- ${displayOld}`,
    `+++ ${displayNew}`,
    `@@ -${hunkRange(oldStart, oldCount)} +${hunkRange(newStart, newCount)} @@`,
    ...before.map((line) => ` ${line}`),
    ...oldChanged.map((line) => `-${line}`),
    ...newChanged.map((line) => `+${line}`),
    ...after.map((line) => ` ${line}`),
  ]
    .filter((line): line is string => line !== undefined)
    .join("\n");
}

function countPatchStats(patch: string): { additions: number; removals: number } {
  let additions = 0;