Don't require using global `core.excludesFile`

[lambdadog]

If borg were to set the core.excludesFile locally for a submodule upon adding it (presumably to a file in-repo), there would be no need to modify your global excludes.

While modifying your global excludes is unlikely to cause issues in most cases, a package could theoretically generate any file on build, including those that would cause conflict with a user's other git repos when excluding them on a global level -- of course, the user could simply set a local value for core.excludesFile in any repo that conflicted with a borg-relevant exclude, but ideally borg would act more as a guest on the user's system and not require them to do so.

[tarsius]

I have mixed feelings about that. I'll think about it at a later time and make a decision then. (Currently I am on break; or am at least trying to.)

[tarsius]

I've added support for defining extra build steps using borg.extra-build-step set in .gitmodules.

You can use that to implement this functionality like so:

# .gitmodules
[borg]
    extra-build-step = (my-borg-add-exclude-rules borg-clone)

;; etc/borg/config.el
(defun my-borg-add-exclude-rules (clone)
  (let ((file (expand-file-name "info/exclude" (borg-gitdir clone))))
    (unless (file-exists-p file)
      (message "Populating %s..." file)
      (make-directory (file-name-directory file))
      (with-temp-file file
        (insert "*.elc\n")
        (insert "*.texi\n")
        (insert "*.info\n")
        (insert "dir\n"))
      (message "Populating %s...done" file))))

[lambdadog]

If anyone else is coming upon this hoping to do the same, the example tarsius shared doesn't work, at least on my system, due to git creating the info/exclude file automatically which causes (file-exists-p file) to always be true.

If you're okay with just overwriting the excludes file every time (not something I'm particularly worried about), I just changed it to the following:

(defun config/borg-add-exclude-rules (clone)
  (let ((file (expand-file-name "info/exclude" (borg-gitdir clone))))
    (message "Populating %s..." file)
    (ignore-errors
      (make-directory (file-name-directory file) 'with-parents))
    (with-temp-file file
      (insert "*.elc\n")
      (insert "*-autoloads.el\n")
      (insert "*.texi\n")
      (insert "*.info\n")
      (insert "dir\n"))
    (message "Populating %s...done" file)))

[lambdadog]

It may also be worth considering just using git config --local core.excludesFile <path> to a singular file shared between all of the drones, but I haven't experimented with that yet.