External files that require multiple extraction steps

[woolsweater]

What would be the recommended way to handle external files that require more elaborate extraction than a single command?

As an example, I'd like make Apple's SF fonts part of my chezmoi-mananged setup. They only distribute these on disk images, which contain compressed archives in a special Apple format. So the steps to install the font files would be something like:

1. Download the disk image
2. Mount it
3. Expand the archive on the image out to a temporary location
4. Copy the actual font files from the expanded directory tree into their destination (~/Library/Fonts/)
5. Unmount the disk image
6. (Ideally but optionally) delete the download

It doesn't seem like this is the kind of process that .chezmoiexternal.filter is intended to support. Which is understandable, since it's rather more than a simple "filter". Is the preferred option therefore to simply use a run_once script to perform the required steps? This is fine but lacks that "declarative" sparkle, so I wanted to double-check. 🙂

Chezmoi is a wonderful tool; thanks for your work!

[twpayne]

One simple solution is to add the extracted font files in ~/Library/Fonts directly to your dotfiles repo, i.e. run

$ chezmoi add ~/Library/Fonts/SF-*.otf

This is declarative, at the expense of making updates to the fonts a manual process.

It would be theoretically possible to use .chezmoiexternal.filter where the filter is a script that you've written that performs the necessary steps to convert the .dmg into a an archive that chezmoi can unpack. However, this would be very inefficient in practice because chezmoi would need to apply the filter every time you run chezmoi diff or chezmoi apply to see if anything has changed.

Although declarative approaches are nice, in practice a run_once_ script is likely the best fit here.

[woolsweater]

That makes sense! I will stick with the run_once script; it does seem like the best option. Thanks!

[twpayne]

Note that in this particular case the .otf files are in a .pkg installer inside the .dmg, so a single unpacking stage is not sufficient.

[halostatue]

True. 7z can probably deal with this, too:

7z e <DMG> <pkgfilename> -so | 7z e -r -si '*.ttf' -o <targetpath>

This is completely untested, and is extremely fragile, obviously.

[woolsweater]

Interesting tip, thanks. I'll keep this in mind for the future.

[twpayne]

Wow, this actually worked. Using 7-Zip 22.01, it actually takes three stages of unpacking (!). I had to go via intermediate files as I think some of the stages require the ability to seek in the input, which you don't get with a pipe.

$ 7zz e -so SF-Mono.dmg "SFMonoFonts/SF Mono Fonts.pkg" > "SF Mono Fonts.pkg"
$ 7zz e -so "SF Mono Fonts.pkg" Payload~ | tar xf - --strip-components=3

[halostatue]

-so outputs to stdout only, so the first line doesn’t need the redirect.

$ 7zz e SF-Mono.dmg "SFMonoFonts/SF Mono Fonts.pkg" # writes "SF Mono Fonts.pkg" to the current directory
$ 7zz e -so "SF Mono Fonts.pkg" Payload~ | tar xf - --strip-components=3