Support ignoring files in the source directory (e.g., under `.chezmoiexternals/`)

[sigprof]

Is your feature request related to a problem? Please describe.

Currently there is no way to make chezmoi ignore some files in source directories like .chezmoiexternals/ or .chezmoitemplates, and this results in some annoyances when dealing with temporary and backup files from editors.

E.g., when vim .chezmoiexternals/chezmoi_modify_manager.toml is running:

$ chezmoi apply 
chezmoi: /home/vsu/.local/share/chezmoi/.chezmoiexternals/.chezmoi_modify_manager.toml.swp: not allowed in .chezmoiexternals directory

And after saving the file and exiting vim (so that the swap file with a problematic name is removed):

$ chezmoi apply 
chezmoi: /home/vsu/.local/share/chezmoi/.chezmoiexternals/chezmoi_modify_manager.toml~: .toml~: unknown format

I have **/*~ and **/.*.sw[a-p] in .chezmoiignore, but these patterns do not get applied to files which are used by chezmoi internally and not installed into the target directory.

Describe the solution you'd like

Ideally chezmoi should just use ignore patterns from .gitignore, but this is probably a too large request. Possible other options are:

• .chezmoisrcignore with the same syntax as .chezmoiignore, but applied to all cases where files from the source directory are read.
• ignoreSourcePatterns = ['**/*~', '**/.*.sw[a-p]'] in the configuration file.

Describe alternatives you've considered

It could be possible to avoid getting extra files written into the source directory, but there are some downsides:

• The editor could be configured to disable backup files when editing files inside ~/.local/share/chezmoi. In this case the downsides are minor (especially given that the files should also be tracked in git).
• Swap files could be disabled too, but in this case the downsides are more annoying, because in Vim swap files also function as lock files to prevent editing the same file in multiple Vim instances, therefore having the swap file in the same directory as the edited file is actually useful. And there is no support for the per-directory configuration of swap files in Vim.

[twpayne]

Ideally chezmoi should just use ignore patterns from .gitignore

This is not feasible. .gitignore files are for configuring git, and chezmoi is not git. .gitignore files also do not give the level of control that chezmoi needs (specifically, chezmoi needs the ability to ignore directories but not the files within them, whereas .gitignore files only apply to files).

The easy fix for you is to configure your editor to save its swap files in a different place, so it does not corrupt chezmoi's source state. In VIM, you can set this with, for example:

:set directory=$HOME/.vim/swapfiles

[sigprof]

There are some precedents for using information from git in other software — e.g., when Nix processes a flake and detects that the flake is in a git worktree, it takes the list of tracked files from git and makes only those files available for evaluation, ignoring any untracked files that may be present in the worktree. (This is actually even stronger than using .gitignore — you can work with a dirty worktree before committing the changes, but you need to git add any newly added files before they become available.)

And :set directory would work, but, unlike the backup-related options, directory is global, and relocating the swapfile to a user-specific directory removes the locking functionality in some multi-user situations. Although the problem with swap files in this particular case would be limited to editing files with names matching chezmoi* (swap files for other file names would be ignored due to initial .).

[twpayne]

Good point. You've changed my mind :)

I propose to make it so that you can put something like

**/.chezmoi*.sw*

in your .chezmoiignore file and that this .chezmoiignore file will also apply to files in chezmoi's special directories.

This way you can tell .chezmoiignore to ignore your editor's swap files, whatever pattern they might have, wherever they are, even if they match chezmoi's "reserved" pattern of .chezmoi*.

Thoughts?

[aforthwith]

I'm interested in this too. Perhaps another use case would help.

Many applications are less than diligent about separating configuration (that I want in my dotfiles) from ephemeral local state (which can be jettisoned, don't need to be backed up). One that I shall not shame supports extensions that can download large node_modules directories.

I'd like to be able to add node_modules to my .chezmoiignore so that I can chezmoi add ~/.local/config/foo without having to be surgical about what's in there that matters. Sometimes it's new files and sometimes it's modified, but I don't want to get distracted and want to lean on my ignore file to help me out. But as it stands, if node_modules is in a subdirectory of what I specify, chezmoi will still add it, which I find a frustrating cognitive dissonance that I keep having to relearn.