Git repository discovery error in monorepo when using Docker

[SimonVreman]

When building my project from the command line locally, just using pnpm next build, repository discovery happens as expected. However, when using Docker, I get a warning:

warn [nextra] Init git repository failed Discover git repo from [/app/docs] failed: could not find repository at '/app/docs'; class=Repository (6); code=NotFound (-3)

Project lives in a monorepo, with docs housing the Nextra app, first level subdirectory, running Nextra 4.2.7. Below is a Dockerfile I used to debug this, with git installed to confirm the repository is copied correctly (run container interactively with sh, run git status in build directory to confirm).

FROM node:20-alpine AS alpine
  RUN apk update
  RUN apk add --no-cache libc6-compat


FROM alpine AS base
  RUN npm install pnpm --global
  RUN pnpm config set store-dir ~/.pnpm-store


FROM base AS deps
  WORKDIR /app/docs
  COPY docs/package.json docs/pnpm-lock.yaml ./
  RUN pnpm i --frozen-lockfile


FROM base AS builder
  RUN apk add --no-cache git
  WORKDIR /app
  COPY .git .git

  WORKDIR /app/docs
  COPY --from=deps /app/docs/node_modules ./node_modules
  COPY ./docs .

  # Build the application
  ENV NEXT_TELEMETRY_DISABLED=1
  RUN pnpm build

[gmoigneu]

I have the same behavior using Upsun PaaS. Not sure what is causing this.