Symlink everything we can find in /usr/lib/firefox

The Arch Linux repositories have many packages which add features
or extensions to Firefox. The AUR has even more. However, all those
packages keep their files inside the `/usr/lib/firefox` hierarchy so
they never worked for `firefox-developer-edition` users.

This commit enables many such extension and feature packages,
for example:

- firefox-noscript
- firefox-ublock-origin
- firefox-extension-multi-account-containers (AUR)

to work with `firefox-developer-edition`.

How it works:

This commit adds install scripts and an ALPM hook. Together, those
scripts and the hook will keep `/usr/lib/firefox` and
`/usr/lib/firefox-developer-edition` in sync. They achieve that by
creating symlinks pointing to each file in the `/usr/lib/firefox`
hierarchy. Pacman will run that hook whenever adding or removing
something in that hierarchy. Pacman will also run the install script
whenever this package gets installed, updated, or removed.

The scripts and the hook will handle the following events:

- When pacman installs anything into the `/usr/lib/firefox` hierarchy
  while this package is installed, the ALPM hook deletes and recreates
  the symlinks.

- The same thing happens when pacman modifies or removes anything in
  the `/usr/lib/firefox` hierarchy while this package is installed.

- When pacman removes the `/usr/lib/firefox` hierarchy while this
  package is installed, the ALPM hook deletes all the symlinks.

- When pacman first installs this package, the install script creates
  the symlinks.

- When pacman updates this package, the install script deletes and
  recreates the symlinks.

- When pacman removes this package, the install script deletes all the
  symlinks.

1 files changed, 12 insertions, 0 deletions

diff --git a/firefox-developer-edition-firefox-symlink.hook b/firefox-developer-edition-firefox-symlink.hook
new file mode 100644
index 000000000000..7e7b6269e5ac
--- /dev/null
+++ b/firefox-developer-edition-firefox-symlink.hook
@@ -0,0 +1,12 @@
+[Trigger]
+Type = Path
+Operation = Install
+Operation = Upgrade
+Operation = Remove
+Target = usr/lib/firefox/*
+
+[Action]
+Description = Updating symlinks for firefox-developer-edition...
+Exec = /bin/bash -c "cd /usr/share/libalpm/scripts && ./firefox-developer-edition-firefox-symlinks-delete && ./firefox-developer-edition-firefox-symlinks-create"
+When = PostTransaction
+Depends = firefox-developer-edition