move ci job scipts into an actual script

This will make it possible/easier to:

* share code between jobs
* run jobs locally

.gitlab-ci.yml

@@ -42,9 +42,7 @@ ci:
     - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH
     - if: $CI_PIPELINE_SOURCE == 'merge_request_event'
   script:
-    - direnv exec . nix-build-and-cache ci
-
-    - direnv exec . engage
+    - direnv exec . job ci
   cache:
     paths:
       - target
@@ -57,7 +55,7 @@ artifacts:
     - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH
     - if: $CI_PIPELINE_SOURCE == 'merge_request_event'
   script:
-    - direnv exec . nix-build-and-cache packages
+    - direnv exec . job artifacts
 
 pages:
   stage: deploy
@@ -65,8 +63,7 @@ pages:
   rules:
     - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH
   script:
-    - nix build .#website-root
-    - cp --recursive --dereference result public
+    - direnv exec . job pages
   artifacts:
     paths:
       - public

bin/job

@@ -0,0 +1,52 @@
+#!/usr/bin/env bash
+
+job_artifacts() (
+    set -euo pipefail
+
+    nix-build-and-cache packages
+)
+
+job_ci() (
+    set -euo pipefail
+
+    nix-build-and-cache ci
+    direnv exec . engage
+)
+
+job_pages() (
+    set -euo pipefail
+
+    nix build .#website-root
+    cp --recursive --dereference result public
+)
+
+bail() (
+    set -euo pipefail
+
+    echo
+    echo "Job failed"
+    exit 1
+)
+
+run() (
+    set -euo pipefail
+
+    if [[ -z "${1+x}" ]]; then
+        echo "You must supply a job to run. Available jobs:"
+        declare -F | rg \
+            --only-matching \
+            --color never \
+            --replace '* $1' \
+            '^declare -f job_(.*)$'
+
+        exit 1
+    fi
+
+    job="$1"
+
+    cd "$(git rev-parse --show-toplevel)"
+
+    job_"$job" || bail
+)
+
+run "$@"

nix/shell.nix

@@ -8,6 +8,7 @@
 , markdownlint-cli
 , mdbook
 , mkShell
+, ripgrep
 , stdenv
 , toolchain
 }:
@@ -35,6 +36,7 @@ mkShell {
     lychee
     markdownlint-cli
     mdbook
+    ripgrep
     toolchain
   ]
   ++