refactor(docker): avoid copying volume inside container (#142)

* refactor(docker): avoid copying volume inside container

* docs(readme): Fix Docker tips to mount project, not just repository

Otherwise any project configs have no chance of being read...

Dockerfile

@@ -15,12 +15,26 @@ RUN cargo build --release --locked --no-default-features
 RUN rm -f target/release/deps/git_cliff*
 
 FROM debian:buster-slim as runner
+
+# Everything inside this container will be explicitly mounted by the end user,
+# so we can sidestep some Git security restrictions. This app recommends
+# mounting data to /app, but this *can* be changed externally and *will* be
+# changed when run by GitHub Actions, so we need to cover our bases.
+RUN echo '[safe]\n\tdirectory = *' > /etc/gitconfig
+
 COPY --from=builder /app/target/release/git-cliff /usr/local/bin
-WORKDIR git-home
-RUN cat <<'EOF' > entrypoint.sh
+WORKDIR app
+
+# Even if the repository as marked as safe, GitHub Actions and some other
+# environments insist on running the entrypoint as root inside the container
+# even when being run by a non priviledged user on their own files. Here we
+# check the ownership of the workdir (which may or may not be /app) and change
+# our effective user/group ID to match.
+RUN cat <<'EOF' > /usr/local/bin/entrypoint.sh
 #!/bin/sh
-cp -r /app /git-home/app
-cd /git-home/app
-exec git-cliff "$@"
+if [ "$(id -u)" -ne "$(stat -c '%u' .)" ]; then
+  eids="$(stat -c '--euid %u --egid %g' .)"
+fi
+exec ${eids:+setpriv --clear-groups $eids} git-cliff $@
 EOF
-ENTRYPOINT ["sh", "entrypoint.sh"]
+ENTRYPOINT ["sh", "/usr/local/bin/entrypoint.sh"]

website/docs/docker.md

@@ -15,13 +15,13 @@ Docker builds are [automated](https://github.com/orhun/git-cliff/tree/main/.gith
 The easiest way of running **git-cliff** (in the git root directory with [configuration file](/docs/configuration) present) is to use the available tags from [Docker Hub](https://hub.docker.com/r/orhunp/git-cliff):
 
 ```bash
-docker run -t -v "$(pwd)/.git":/app/ "orhunp/git-cliff:${TAG:-latest}"
+docker run -t -v "$(pwd)":/app/ "orhunp/git-cliff:${TAG:-latest}"
 ```
 
 Or you can use the image from the [GitHub Package Registry](https://github.com/orhun/git-cliff/pkgs/container/git-cliff%2Fgit-cliff):
 
 ```bash
-docker run -t -v "$(pwd)/.git":/app/ "ghcr.io/orhun/git-cliff/git-cliff:${TAG:-latest}"
+docker run -t -v "$(pwd)":/app/ "ghcr.io/orhun/git-cliff/git-cliff:${TAG:-latest}"
 ```
 
 ### Building