Add a GitHub Action to lint my Caddyfiles

.github/workflows/caddy_fmt.yml

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+name: "Lint my Caddyfiles"
+
+on:
+  push:
+    branches:
+    - main
+
+    paths:
+      - '.github/workflows/caddy_fmt.yml'
+      - 'Caddyfile'
+      - '**/Caddyfile'
+      - '**/*.Caddyfile'
+
+  pull_request:
+    branches:
+    - main
+
+    paths:
+      - '.github/workflows/caddy_fmt.yml'
+      - 'Caddyfile'
+      - '**/Caddyfile'
+      - '**/*.Caddyfile'
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - name: "Check out the repo"
+        uses: actions/checkout@v4
+
+      - name: Install Caddy
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          gh release download \
+            --repo caddyserver/caddy \
+            --pattern 'caddy_*_linux_amd64.tar.gz' \
+            --output caddy.tar.gz
+          tar -xzf caddy.tar.gz --directory /usr/local/bin
+          chmod +x /usr/local/bin/caddy
+          which caddy
+
+      - name: Format my Caddyfiles
+        run: |
+          find . \
+            -name Caddyfile \
+            -o -name '*.Caddyfile' ! -name 'redirects.Caddyfile' | \
+            xargs -I '{}' --verbose caddy fmt --overwrite '{}'
+
+      - name: Print changes
+        run: git diff
+
+      - name: Check for changes
+        run: git diff --exit-code

src/_til/2024/2024-11-22-debugging-find-and-xargs.md

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+---
+layout: til
+title: Debugging some confusing behaviour with `find` and `xargs`
+date: 2024-11-22 16:35:11 +0000
+tags:
+  - shell scripting
+summary:
+  Use the `--verbose` flag to see what `xargs` is doing; don't rely on `find` to return files in a consistent order.
+---
+I was trying to write a GitHub Actions workflow to format my Caddyfiles.
+I'd written a command to find all the Caddyfiles in my repo, and pass them to `caddy fmt`:
+
+```
+find . -name Caddyfile | xargs caddy fmt --overwrite
+```
+
+Thsi command seemed to work when I ran it locally on my Mac, but it didn't do what I expected when it ran on Ubuntu in GitHub Actions.
+It took me a while to work out what was going on!
+
+I learnt two useful debugging techniques along the way:
+
+1.  **Use the `--verbose` flag to see what `xargs` is doing.**
+    This will print the exact command which is run by `xargs`.
+
+    ```console
+    $ ls *.jpg | xargs echo
+    26704189108_9e71d865d8_b.jpg 51119071159_905212c30f_b.jpg 8076936667_c5605863a9_o.jpg
+
+    $ ls *.jpg | xargs --verbose echo
+    echo 26704189108_9e71d865d8_b.jpg 51119071159_905212c30f_b.jpg 8076936667_c5605863a9_o.jpg
+    26704189108_9e71d865d8_b.jpg 51119071159_905212c30f_b.jpg 8076936667_c5605863a9_o.jpg
+
+    $ ls *.jpg | xargs --verbose -I '{}' echo '{}'
+    echo 26704189108_9e71d865d8_b.jpg
+    26704189108_9e71d865d8_b.jpg
+    echo 51119071159_905212c30f_b.jpg
+    51119071159_905212c30f_b.jpg
+    echo 8076936667_c5605863a9_o.jpg
+    8076936667_c5605863a9_o.jpg
+    ```
+
+    In particular, I could see whether the command I was running with `xargs` was being called with all the arguments at once, or passed them individually.
+
+2.  **Files discovered by `find` may be in a different order on different OSes.**
+
+    This was the heart of my issue -- I was passing all my filenames in one big list, and `caddy fmt` will [only format the first path it gets](https://github.com/caddyserver/caddy/issues/6702).
+    Because the order of files is different on different OSes, I was getting different behaviour.
+
+    Compare:
+
+    ```console
+    $ # macOS
+    $ find . -name Caddyfile -o -name '*.Caddyfile'
+    ./Caddyfile
+    ./caddy/gone.Caddyfile
+    ./caddy/redirects.Caddyfile
+
+    $ # Ubuntu
+    $ find . -name Caddyfile -o -name '*.Caddyfile'
+    ./caddy/gone.Caddyfile
+    ./caddy/redirects.Caddyfile
+    ./Caddyfile
+    ```
+
+    In hindsight, this makes sense -- there are multiple ways you might search a directory tree, and one isn't necessarily better than the other.
+
+    Don't rely on the order to be consistent!
+
+    I've had a brief glance at the man page, and `find` does have some options for controlling the ordering -- for example, you can use `-d`/`--depth` to do a depth-first search (process each directory's contents before the directory itself).
+
+    This reminds me of when I discovered `WalkDir::contents_first()` and `os.walk(topdown: bool)` while [writing `emptydir`](/2024/emptydir/#how-does-it-work).

src/_til/2024/2024-11-22-install-from-github-releases.md

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+---
+layout: til
+title: How to install an asset from a GitHub release
+date: 2024-11-22 11:35:50 +0000
+tags:
+  - github
+summary:
+  Use `gh release download`, which includes a pattern matcher if you want to pick a specific asset.
+---
+I wanted to install Caddy in GitHub Actions, and one of the ways [to install it](https://caddyserver.com/docs/install#static-binaries) is by downloading static binaries from their GitHub releases.
+
+I wasn't sure how to download release assets in a sensible way -- I've written shell scripts for it before, but it feels messy and fragile.
+Surely there must be a better way!
+
+I stumbled upon [a GitHub Action](https://github.com/php/php-src/blob/master/.github/actions/setup-caddy/action.yml) in the PHP repository (!) which pointed me in the right direction:
+
+```shell
+gh release -R caddyserver/caddy download --pattern 'caddy_*_linux_amd64.tar.gz' -O - | sudo tar -xz -C /usr/bin caddy
+sudo chmod +x /usr/bin/caddy
+```
+
+This is using [the GitHub CLI](https://cli.github.com/), which I haven't used before -- but it's pre-installed in GitHub Actions, which is very convenient for my purposes!
+
+## In a GitHub Action
+
+Here's how I packaged this as a step in a GitHub Action:
+
+```yml
+- name: Install Caddy
+  env:
+    GH_TOKEN: ${{ github.token }}
+  run: |
+    gh release download \
+      --repo caddyserver/caddy \
+      --pattern 'caddy_*_linux_amd64.tar.gz' \
+      --output caddy.tar.gz
+    tar -xzf caddy.tar.gz --directory /usr/local/bin
+    chmod +x /usr/local/bin/caddy
+    which caddy
+```
+
+It's a bit more verbose and leaves a `caddy.tar.gz` file lying around, but I find this version easier to understand and debug.
+
+## Notes
+
+*   You can specific a release to `gh release download`, or if not it will pick the latest release.
+    If you let it pick automatically, it skips pre-releases.