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Loading the Emacs Info manuals in MSYS2

4 July 2021 3:58 AM (emacs | msys2 | windows)

I've been annoyed at MSYS2 for a while because Info manuals included with Emacs wouldn't show up when I opened info. The few manuals that were installed through ELPA packages showed up fine.

Some time ago I discovered this was because I installed the mingw-w64-x86_64-emacs package from MSYS2, and this package installs all the info manuals into /mingw64/share/info instead of /usr/share/info and there was no dir file in there. I couldn't quite remember how this worked so I left it alone. At least I understood what was going on.

Recently I finally took the time to look at it again. I remembered that pacman has some capabilities for hooks. I wrote a very simple one for myself to keep my Pacman mirror list updated automatically. But I couldn't remember where the default ones were located. pacman to the rescue. pacman -Ql pacman | less with a quick search for hooks and I discovered that these hooks live in /usr/share/libalpm/hooks/. A quick look in there showed that MSYS2 distributes a couple of hooks: texinfo-install.hook and texinfo-remove.hook. When a package gets installed, upgraded, or removed one of these hooks gets called.

Basically what the -install hook does is go through each file in the installed packages that is under /usr/share/info and call install-info on it. That's great, easy to reproduce on the command line:

find /mingw64/share/info -fype f -name '*.info' -exec install-info '{}' /mingw64/share/info/dir \;

This sets it up the first time, since I already have Emacs installed and didn't want to reinstall it.

[Trigger]
Type = Path
Operation = Install
Operation = Upgrade
Target = mingw64/share/info/*

[Action]
Description = Updating the mingw64 info directory file...
When = PostTransaction
Exec = /usr/bin/sh -c 'while read -r f; do install-info "$f" /mingw64/share/info/dir 2> /dev/null; done'
NeedsTargets

Put this in /etc/pacman.d/hooks/texinfo-install-mingw64.hook (or C:/msys2/etc/pacman.d/hooks/texinfo-install-mingw64.hook if you're working from Emacs), and now every time a package gets installed or upgraded and it has any files in /mingw64/share/info/ it should automatically update the dir file and give you access to all those info manuals.

The remove hook is basically the same, except it passes in the --delete option to install-info to remove the entries from the dir file.

[Trigger]
Type = Path
Operation = Remove
Target = mingw64/share/info/*

[Action]
Description = Removing old entries from the mingw64 info directory file...
When = PreTransaction
Exec = /usr/bin/sh -c 'while read -r f; do install-info --delete "$f" /mingw64/share/info/dir 2> /dev/null; done'
NeedsTargets

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