feat: Add an entrypoint to perform env setup

Author: tlater-famedly

Diff for: Dockerfile

@@ -25,3 +25,6 @@ RUN apt update -yqq \
      && cargo install cargo-license \
      && cargo cache -a
 COPY cobertura_transform.xslt /opt/
+
+COPY entrypoint.bash /entrypoint.bash
+ENTRYPOINT ["/entrypoint.bash"]

Diff for: README.md

@@ -0,0 +1,15 @@
+# Famedly Rust Container
+
+Container used for Rust CI jobs. Set up with all necessary packages
+and configuration to build, test and publish our crates.
+
+For full environment setup, some secrets need to be defined:
+
+## Settings
+
+| Variable                     | Example Value                                     | Explanation                                                           |
+|------------------------------|---------------------------------------------------|-----------------------------------------------------------------------|
+| FCR_ADDITIONAL_RUST_PACKAGES | cargo-fuzz cargo-tarpaulin                        | Additional Rust packages to install before running the given command. |
+| FCR_CRATES_REGISTRY          | famedly                                           | Additional registry to pull crates from.                              |
+| FCR_CRATES_REGISTRY_INDEX    | ssh://[email protected]/famedly/crate-index.git | The index URL of the registry; Can be omitted for `famedly`.          |
+| FCR_SSH_KEY                  |                                                   | The SSH key to use                                                    |

Diff for: entrypoint.bash

@@ -0,0 +1,82 @@
+#!/bin/bash
+
+# Famedly Rust Container entrypoint.
+#
+# Configures the runtime to be used for various CI jobs.
+
+echo "Preparing Rust build environment"
+
+
+if [ -n "${FCR_SSH_KEY}" ]; then
+    echo "Setting up SSH"
+
+    # Get an ssh agent running
+    USER="$(whoami)"
+    SSH_HOME="$(getent passwd "$USER" | cut -d: -f6)" # Is different from $HOME in docker containers, because github CI..
+    eval "$(ssh-agent)" # This exports the socket to `SSH_AUTH_SOCK`
+
+    # Import the SSH key from the secret
+    ssh-add -vvv - <<< "${FCR_SSH_KEY}"$'\n' # ensure newline at the end of key
+
+    # Import host keys for GitHub and Gitlab
+    mkdir -p "$SSH_HOME/.ssh"
+    (
+        ssh-keyscan -H gitlab.com
+        ssh-keyscan -H github.com
+    ) >> "$SSH_HOME/.ssh/known_hosts"
+fi
+
+
+if [ -n "${FCR_ADDITIONAL_RUST_PACKAGES}" ]; then
+    echo "Installing additional packages: ${FCR_ADDITIONAL_RUST_PACKAGES}"
+    # shellcheck disable=SC2086
+    apt-get install -yqq --no-install-recommends ${FCR_ADDITIONAL_RUST_PACKAGES}
+fi
+
+
+echo "Configuring cargo"
+
+CARGO_HOME="${HOME}/${CARGO_HOME}"
+mkdir -p "${CARGO_HOME}"
+cat << EOF >> "${CARGO_HOME}/config.toml"
+[net]
+git-fetch-with-cli = true
+EOF
+
+# Don't write anything for crates-io, since it is baked-in and cargo
+# special cases on it so configuring it works differently anyway.
+if [ -n "${FCR_CRATES_REGISTRY}" ] &&  [ "${FCR_CRATES_REGISTRY}" != "crates-io" ]; then
+    case "${FCR_CRATES_REGISTRY}" in
+        "famedly")
+            FCR_CRATES_REGISTRY_INDEX="${FCR_CRATES_REGISTRY_INDEX:-ssh://git@ssh.shipyard.rs/famedly/crate-index.git}"
+            ;;
+        "")
+            if [ -z "${FCR_CRATES_REGISTRY_INDEX}" ]; then
+                echo "Error: Crate registry index URL not known for ${FCR_CRATES_REGISTRY}. Configure it using \$FCR_CRATES_REGISTRY_INDEX." > /dev/stderr
+                exit 1
+            fi
+            ;;
+    esac
+
+    cat << EOF >> "${CARGO_HOME}/config.toml"
+[registries.${FCR_CRATES_REGISTRY}]
+index = "${FCR_CRATES_REGISTRY_INDEX}"
+EOF
+fi
+
+
+if [ -n "${GITHUB_ENV}" ]; then
+    # TODO(tlater): Check if this is even necessary; AIUI we should
+    # remain in the container env and therefore these variables should
+    # already be set.
+    echo "Exporting created environment variables"
+
+    (
+        echo "CARGO_HOME=${CARGO_HOME}"
+        echo "SSH_AUTH_SOCK=${SSH_AUTH_SOCK}"
+    ) >> "$GITHUB_ENV"
+fi
+
+
+echo "Preparations finished"
+"$@"