Run script when external changes

[chuxubank]

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

I'm always frustrated when I want to run a script after an external changes like git-repo

Describe the solution you'd like

Provide external's status in the chezmoi data.
For git-repo it could be the current latest commit id,
For others it could be the checksum or other things.
So I can include something like

{{ .chezmoi.external.".emacs.d".status }}

or
add templete function like git

{{ gitStatus "~/.emacs.d" }}

and for dir

{{ dirHash "~/.emacs.d" }}

in my scripts and only run them if the external changes with run_on_change prefix.

Describe alternatives you've considered

Give an run_on_external_change prefix for script.
Could following by an external name like run_on_external_change_dot_emacs_d

Additional context

It could be helpful if we want run script only when the external changes.

[ErrrorMaxx]

I think {{ "output" "git" "-C" "~/.emacs.d" "rev-parse" "HEAD" }} for git-repo is ok

[chuxubank]

@ErrrorMaxx Thanks! Seemed I missed the output function.

[chuxubank]

For others, the final version could be:

{{ output "git" "-C" (joinPath .chezmoi.homeDir ".emacs.d") "rev-parse" "HEAD" }}