Add %-specifiers support.

lacme(8): for --config=, --socket=, --config-certs= (and ‘socket’/
‘config-certs’/‘challenge-directory’ configuration options *before*
privilege drop; and for the [accountd] section ‘command’/‘config’
configuration options *after* privilege drop).

lacme-accountd(1): for --config=, --socket= and --privkey= (and
‘socket’/‘privkey’ configuration options).

This also changes the default configuration file location.  lacme(8) and
lacme-accountd(1) now respectively use /etc/lacme/lacme.conf resp.
/etc/lacme/lacme-accountd.conf when running as root, and
$XDG_CONFIG_HOME/lacme/lacme.conf resp. $XDG_CONFIG_HOME/lacme/lacme-accountd.conf
when running as a normal user.  There is no fallback to /etc anymore.

1 files changed, 53 insertions, 14 deletions

diff --git a/lacme-accountd.1.md b/lacme-accountd.1.md
index cd6352c..4c494f2 100644
--- a/lacme-accountd.1.md
+++ b/lacme-accountd.1.md
@@ -41,9 +41,12 @@ Options
 
 `--config=`*filename*
 
-:   Use *filename* as configuration file.  `lacme-accountd` fails when
-    `--config=` is used with a non-existent file, but a non-existent
-    default location is treated as if it were an empty file.
+:   Use *filename* as configuration file instead of
+    `%E/lacme/lacme-accountd.conf`.  The value is subject to
+    [%-specifier expansion](#percent-specifiers).  `lacme-accountd`
+    fails when `--config=` is used with a non-existent file, but a
+    non-existent default location is treated as if it were an empty
+    file.
 
     See the **[configuration file](#configuration-file)** section below
     for the configuration options.
@@ -57,6 +60,8 @@ Options
       symmetrically encrypted)
     * `gpg:`*FILE*, for a [`gpg`(1)]-encrypted private key
 
+    *FILE* is subject to [%-specifier expansion](#percent-specifiers).
+
     The [`genpkey`(1ssl)] command can be used to generate a new private
     (account) key:
 
@@ -67,9 +72,14 @@ Options
 
 `--socket=`*path*
 
-:   Use *path* as the UNIX-domain socket to bind against for signature
-    requests from the [ACME] client.  `lacme-accountd` aborts if *path*
-    exists or if its parent directory is writable by other users.
+:   Use *path* as the UNIX-domain socket to bind to for signature
+    requests from the [ACME] client.  The value is subject to
+    [%-specifier expansion](#percent-specifiers).  `lacme-accountd`
+    aborts if *path* exists or if its parent directory is writable by
+    other users.
+    Default: `%t/S.lacme` (omitting `--socket=` therefore yields an
+    error when `lacme-accountd` doesn't run as and the `XDG_RUNTIME_DIR`
+    environment variable is unset or empty).
 
 `-h`, `--help`
 
@@ -86,12 +96,6 @@ Options
 Configuration file
 ==================
 
-If `--config=` is not given, `lacme-accountd` uses the first existing
-configuration file among *$XDG_CONFIG_HOME/lacme/lacme-accountd.conf*
-(or *~/.config/lacme/lacme-accountd.conf* if the `XDG_CONFIG_HOME`
-environment variable is not set), and
-*@@sysconfdir@@/lacme/lacme-accountd.conf*.
-
 When given on the command line, the `--privkey=`, `--socket=` and
 `--quiet` options take precedence over their counterpart (without
 leading `--`) in the configuration file.  Valid settings are:
@@ -110,13 +114,48 @@ leading `--`) in the configuration file.  Valid settings are:
 *socket*
 
 :   See `--socket=`.
-    Default: *$XDG_RUNTIME_DIR/S.lacme* if the `XDG_RUNTIME_DIR`
-    environment variable is set.
 
 *quiet*
 
 :   Be quiet. Possible values: `Yes`/`No`.
 
+%-specifiers  {#percent-specifiers}
+============
+
+The value the `--config=`, `--privkey=` and `--socket=` CLI options (and
+*privkey* and *socket* configuration options) are subject to %-expansion
+for the following specifiers.
+
+----  ------------------------------------------------------------------
+`%C`  `@@localstatedir@@/cache` for the root user, and `$XDG_CACHE_HOME`
+      for other users (or `$HOME/.cache` if the `XDG_CACHE_HOME`
+      environment variable is unset or empty).
+
+`%E`  `@@sysconfdir@@` for the root user, and `$XDG_CONFIG_HOME` for
+      other users (or `$HOME/.config` if the `XDG_CONFIG_HOME`
+      environment variable is unset or empty).
+
+`%g`  Current group name.
+
+`%G`  Current group ID.
+
+`%h`  Home directory of the current user.
+
+`%t`  `@@runstatedir@@` for the root user, and `$XDG_RUNTIME_DIR` for
+      other users.  Non-root users may only use `%t` when the
+      `XDG_RUNTIME_DIR` environment variable is set to a non-empty
+      value.
+
+`%T`  `$TMPDIR`, or `/tmp` if the `TMPDIR` environment variable is unset
+      or empty.
+
+`%u`  Current user name.
+
+`%U`  Current user ID.
+
+`%%`  A literal `%`.
+----  ------------------------------------------------------------------
+
 Examples
 ========