Document solution to "docs last update" date being rendered incorrectly when published through Vercel

[granny]

Have you read the Contributing Guidelines on issues?

• I have read the Contributing Guidelines on issues.

Description

Setting the VERCEL_DEEP_CLONE environment variable to true through vercel's Project Settings page will fix the "docs last update" date being rendered incorrectly when published through Vercel.

It should be documented in the field description of showLastUpdateTime.

It should also be documented under Deploying to Vercel. (I understand the decision to keep the "deployment" section mostly as-is.)

An aside:

A broader approach/solution would involve outputting a warning in the console if the repository is shallow and the showLastUpdateTime field is enabled. The warning would include the relevant solution for GitHub Actions or Vercel, depending on which one is being used.

Self-service

• I'd be willing to address this documentation request myself.