Add $EUDEV_RULES_DIRECTORY to the list of rules directories.

The old udev 182 supported $UDEV_CONFIG_FILE, which in turn allowed
the search path to be customized, but eudev no longer has this, hence
this hack.

--- eudev-3.1.5/src/udev/udev-rules.c	2015-10-13 06:22:14.000000000 +0800
+++ eudev-3.1.5/src/udev/udev-rules.c	2015-10-16 20:45:38.491934336 +0800
@@ -47,15 +47,11 @@
         };
 };
 
-static const char* const rules_dirs[] = {
+static const char* rules_dirs[] = {
         UDEV_CONF_DIR "/rules.d",
         UDEV_RULES_DIR,
-        UDEV_ROOT_RUN "/udev/rules.d",
         UDEV_LIBEXEC_DIR "/rules.d",
-#ifdef HAVE_SPLIT_USR
-        "/lib/udev/rules.d",
-        "/usr/lib/udev/rules.d",
-#endif
+        NULL,			/* placeholder for $EUDEV_RULES_DIRECTORY */
         NULL};
 
 struct udev_rules {
@@ -1704,6 +1700,9 @@
 
         udev_rules_check_timestamp(rules);
 
+        /* Allow the user to specify an additional rules directory.  */
+        rules_dirs[3] = getenv("EUDEV_RULES_DIRECTORY");
+
         r = conf_files_list_strv(&files, ".rules", NULL, rules_dirs);
         if (r < 0) {
                 log_error_errno(r, "failed to enumerate rules files: %m");
og/tests/services.scm'>log</a><a href='/guix/tree/tests/services.scm?id=05044a54468e091ead1dfa24662df02cd0929ad8'>tree</a><a href='/guix/commit/tests/services.scm?id=05044a54468e091ead1dfa24662df02cd0929ad8'>commit</a><a href='/guix/diff/tests/services.scm?id=05044a54468e091ead1dfa24662df02cd0929ad8'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/tests/services.scm'>
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<div class='path'>path: <a href='/guix/log/?id=05044a54468e091ead1dfa24662df02cd0929ad8'>root</a>/<a href='/guix/log/tests?id=05044a54468e091ead1dfa24662df02cd0929ad8'>tests</a>/<a href='/guix/log/tests/services.scm?id=05044a54468e091ead1dfa24662df02cd0929ad8'>services.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/tests/services.scm?id=05044a54468e091ead1dfa24662df02cd0929ad8&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2023-06-06 11:54:39 +0200'>2023-06-06</span></td><td><a href='/guix/commit/tests/services.scm?id=181951207339508789b28ba7cb914f983319920f'>services: 'modify-services' preserves service ordering.</a><span class='msg-avail'>...<span class='msg-tooltip'>Fixes &lt;https://issues.guix.gnu.org/63921&gt;.

The regression was introduced in
dbbc7e946131ba257728f1d05b96c4339b7ee88b, which changed the order of
services.  As a result, someone using 'modify-services' could find
themselves with incorrect ordering of expressions in the "boot" script,
whereby the cleanup expressions would come after (execl ".../shepherd").
This, in turn, would lead shepherd to error out at boot with EADDRINUSE
on /var/run/shepherd/socket.

* gnu/services.scm (%delete-service, %apply-clauses): Remove.
(clause-alist): New macro.
(apply-clauses): New procedure.
(modify-services): Use it.  Adjust docstring.
* tests/services.scm ("modify-services: do nothing"): Remove 'sort' call.
("modify-services: delete service"): Likewise, and add 't4' service.
("modify-services: change value"): Remove 'sort' call and fix expected value.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2023-06-02 16:16:12 +0200'>2023-06-02</span></td><td><a href='/guix/commit/tests/services.scm?id=ae707b62e71b1fae054eb422412384bcc8d39fa9'>tests: Check for service existence in MODIFY-SERVICES</a><span class='msg-avail'>...<span class='msg-tooltip'>* tests/services.scm ("modify-services: delete non-existing service")
("modify-services: change value for non-existing service"): New tests.

Signed-off-by: Ludovic Courtès &lt;ludo@gnu.org&gt;
</span></span></td><td>Brian Cully</td></tr>
<tr><td><span title='2023-06-02 16:16:07 +0200'>2023-06-02</span></td><td><a href='/guix/commit/tests/services.scm?id=09fcf261c1f66a07891ec2fe80f8652fd286bd3e'>tests: Add tests for MODIFY-SERVICES procedure</a><span class='msg-avail'>...<span class='msg-tooltip'>* tests/services.scm ("modify-services: do nothing")
("modify-services: delete service")
("modify-services: change value"): New tests.

Signed-off-by: Ludovic Courtès &lt;ludo@gnu.org&gt;
</span></span></td><td>Brian Cully</td></tr>
<tr><td><span title='2022-05-18 22:29:54 +0200'>2022-05-18</span></td><td><a href='/guix/commit/tests/services.scm?id=3948ac25b1dccc40c7fdf56377f94a0775a835ee'>services: Make &lt;service-type&gt; 'description' field mandatory.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services.scm (&lt;service-type&gt;)[description]: Remove default value.
* tests/services.scm: Add 'description' field to each 'service-type' form.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-04-10 01:24:30 +0200'>2022-04-10</span></td><td><a href='/guix/commit/tests/services.scm?id=ec6a585ee2fd91c857276479411eedd0756e0093'>services: Test 'shepherd-service-upgrade' with transient services.</a><span class='msg-avail'>...<span class='msg-tooltip'>This is a followup to eeb8ac43c8c0b0cc69422766070dbefc55f5c5c1.

* tests/services.scm ("shepherd-service-upgrade: transient service"):
New test.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-04-10 01:15:13 +0200'>2022-04-10</span></td><td><a href='/guix/commit/tests/services.scm?id=e25eca35ff04e4234d0376fbb9a8e146869772c8'>services: herd: Adjust to &lt;live-service&gt; changes.</a><span class='msg-avail'>...<span class='msg-tooltip'>This is a followup to a2c759c8304c461d096ab763568e7f71546ff4e8.

* guix/scripts/system/reconfigure.scm (running-services): Fill in the
'transient?' field of &lt;live-service&gt;.
* tests/services.scm ("shepherd-service-upgrade: one unchanged, one upgraded, one new")
("shepherd-service-upgrade: service depended on is not unloaded")
("shepherd-service-upgrade: obsolete services that depend on each
other"): Adjust calls to 'live-service'.
</span></span></td><td>Ludovic Courtès</td></tr>