bug#65927: the role and location of locale.alias

[Bruno Haible <bruno@clisp.org>]

Hi,

In guix 1.4.0 there are 2 locale.alias files from glibc on the disk:

$ ls -liL --sort=size `find / -name locale.alias 2>/dev/null | grep -v X11` 940417 -r--r--r-- 1 root root 2998 Jan  1  1970 /gnu/store/0dbscs8zq4bdg8vbn9jkdgynjcn3s01p-gcc-toolchain-12.2.0/share/locale/locale.alias
 940417 -r--r--r-- 1 root root 2998 Jan  1  1970 /gnu/store/5h2w4qi9hk1qzzgi1w83220ydslinr4s-glibc-2.33/share/locale/locale.alias
  15716 -r--r--r-- 1 root root 2998 Jan  1  1970 /gnu/store/ayc9r7162rphy4zjw8ch01pmyh214h82-glibc-2.33/share/locale/locale.alias
  15716 -r--r--r-- 1 root root 2998 Jan  1  1970 /gnu/store/c326489r6jvnl69l2nbmdvxmgzqln2hy-profile/share/locale/locale.alias
  15716 -r--r--r-- 1 root root 2998 Jan  1  1970 /gnu/store/isn13ca7419sj7myb3xr3i3zbxspky8c-profile/share/locale/locale.alias
  15716 -r--r--r-- 1 root root 2998 Jan  1  1970 /gnu/store/yh51nb5dq9n6pw8mrdp3nxcfmxzmrp1x-profile/share/locale/locale.alias
1058938 -r--r--r-- 1 root root  261 Jan  1  1970 /gnu/store/wf46adk80fdc1qij8472n8r2xr4cln0a-gdm-42.0/share/gdm/locale.alias

I explained the purpose of this file in
https://sourceware.org/pipermail/libc-alpha/2023-September/151524.html .
In summary, it's a configuration file whose initial contents is provided
for glibc, but which needs to be edited by the system administrator in
some situations.

For this reason, in Debian 12, the file has been moved to
/etc/locale.alias, and /usr/share/locale/locale.alias is merely
a symbolic link to /etc/locale.alias. IMO, this is the correct
way to handle this configuration file.

The way Guix handles this file provokes two problems:

1) When the system administrator wants to add a new alias, they have
   to search for all occurrences of the file in the (two) glibc
   installations. And if/when they install newer versions of glibc,
   they will have to reapply their change again and again.

2) GNU gettext needs to access this file, in order to recognize the
   same aliases that glibc recognizes. But glibc does not export the
   _nl_expand_alias function. Therefore GNU gettext needs to know
   where the file is. But how could GNU gettext retrieve any of the
   file names
     /gnu/store/5h2w4qi9hk1qzzgi1w83220ydslinr4s-glibc-2.33/share/locale/locale.alias
     /gnu/store/ayc9r7162rphy4zjw8ch01pmyh214h82-glibc-2.33/share/locale/locale.alias
   ?
   If Guix had this configuration file moved to /etc, like Debian did, GNU gettext
   could be compiled with '-DLOCALE_ALIAS_PATH=\"/etc\"' and would then be able
   to access it.

Bruno