man: move examples out of sd_journal_get_fd into separate files

man/.dir-locals is to keep indentation under control.

This makes it much easier to compile and run those examples, c.f. #7578.

v2:
- copy more of .dir-locals.el from the root to man/.dir-locals.el
  (I though emacs would inherit from the one in the parent dir, but
   it seems it just uses its own broken defaults, including
   indent-tabs-mode by default.)

man/.dir-locals.el

@@ -0,0 +1,14 @@
+; special .c mode with reduced indentation for man pages
+((nil . ((indent-tabs-mode . nil)
+         (tab-width . 8)
+         (fill-column . 79)))
+ (c-mode . ((fill-column . 80)
+            (c-basic-offset . 2)
+            (eval . (c-set-offset 'substatement-open 0))
+            (eval . (c-set-offset 'statement-case-open 0))
+            (eval . (c-set-offset 'case-label 0))
+            (eval . (c-set-offset 'arglist-intro '++))
+            (eval . (c-set-offset 'arglist-close 0))))
+ (nxml-mode . ((nxml-child-indent . 2)
+               (fill-column . 119)))
+ (meson-mode . ((meson-indent-basic . 8))))

man/journal-iterate-poll.c

@@ -0,0 +1,23 @@
+#include <poll.h>
+#include <systemd/sd-journal.h>
+
+int wait_for_changes(sd_journal *j) {
+  struct pollfd pollfd;
+  int msec;
+
+  sd_journal_get_timeout(m, &t);
+  if (t == (uint64_t) -1)
+    msec = -1;
+  else {
+    struct timespec ts;
+    uint64_t n;
+    clock_gettime(CLOCK_MONOTONIC, &ts);
+    n = (uint64_t) ts.tv_sec * 1000000 + ts.tv_nsec / 1000;
+    msec = t > n ? (int) ((t - n + 999) / 1000) : 0;
+  }
+
+  pollfd.fd = sd_journal_get_fd(j);
+  pollfd.events = sd_journal_get_events(j);
+  poll(&pollfd, 1, msec);
+  return sd_journal_process(j);
+}

man/journal-iterate-wait.c

@@ -0,0 +1,39 @@
+#include <stdio.h>
+#include <string.h>
+#include <systemd/sd-journal.h>
+
+int main(int argc, char *argv[]) {
+  int r;
+  sd_journal *j;
+  r = sd_journal_open(&j, SD_JOURNAL_LOCAL_ONLY);
+  if (r < 0) {
+    fprintf(stderr, "Failed to open journal: %s\n", strerror(-r));
+    return 1;
+  }
+  for (;;)  {
+    const void *d;
+    size_t l;
+    r = sd_journal_next(j);
+    if (r < 0) {
+      fprintf(stderr, "Failed to iterate to next entry: %s\n", strerror(-r));
+      break;
+    }
+    if (r == 0) {
+      /* Reached the end, let's wait for changes, and try again */
+      r = sd_journal_wait(j, (uint64_t) -1);
+      if (r < 0) {
+        fprintf(stderr, "Failed to wait for changes: %s\n", strerror(-r));
+        break;
+      }
+      continue;
+    }
+    r = sd_journal_get_data(j, "MESSAGE", &d, &l);
+    if (r < 0) {
+      fprintf(stderr, "Failed to read message field: %s\n", strerror(-r));
+      continue;
+    }
+    printf("%.*s\n", (int) l, (const char*) d);
+  }
+  sd_journal_close(j);
+  return 0;
+}

man/sd_journal_get_fd.xml

@@ -23,7 +23,7 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 -->
 
-<refentry id="sd_journal_get_fd">
+<refentry id="sd_journal_get_fd" xmlns:xi="http://www.w3.org/2001/XInclude">
 
   <refentryinfo>
     <title>sd_journal_get_fd</title>
@@ -263,73 +263,13 @@ else {
     <para>Iterating through the journal, in a live view tracking all
     changes:</para>
 
-    <programlisting>#include &lt;stdio.h&gt;
-#include &lt;string.h&gt;
-#include &lt;systemd/sd-journal.h&gt;
-
-int main(int argc, char *argv[]) {
-  int r;
-  sd_journal *j;
-  r = sd_journal_open(&amp;j, SD_JOURNAL_LOCAL_ONLY);
-  if (r &lt; 0) {
-    fprintf(stderr, "Failed to open journal: %s\n", strerror(-r));
-    return 1;
-  }
-  for (;;)  {
-    const void *d;
-    size_t l;
-    r = sd_journal_next(j);
-    if (r &lt; 0) {
-      fprintf(stderr, "Failed to iterate to next entry: %s\n", strerror(-r));
-      break;
-    }
-    if (r == 0) {
-      /* Reached the end, let's wait for changes, and try again */
-      r = sd_journal_wait(j, (uint64_t) -1);
-      if (r &lt; 0) {
-        fprintf(stderr, "Failed to wait for changes: %s\n", strerror(-r));
-        break;
-      }
-      continue;
-    }
-    r = sd_journal_get_data(j, "MESSAGE", &amp;d, &amp;l);
-    if (r &lt; 0) {
-      fprintf(stderr, "Failed to read message field: %s\n", strerror(-r));
-      continue;
-    }
-    printf("%.*s\n", (int) l, (const char*) d);
-  }
-  sd_journal_close(j);
-  return 0;
-}</programlisting>
+    <programlisting><xi:include href="journal-iterate-wait.c" parse="text" /></programlisting>
 
     <para>Waiting with <function>poll()</function> (this
     example lacks all error checking for the sake of
     simplicity):</para>
 
-    <programlisting>#include &lt;poll.h&gt;
-#include &lt;systemd/sd-journal.h&gt;
-
-int wait_for_changes(sd_journal *j) {
-  struct pollfd pollfd;
-  int msec;
-
-  sd_journal_get_timeout(m, &amp;t);
-  if (t == (uint64_t) -1)
-    msec = -1;
-  else {
-    struct timespec ts;
-    uint64_t n;
-    clock_gettime(CLOCK_MONOTONIC, &amp;ts);
-    n = (uint64_t) ts.tv_sec * 1000000 + ts.tv_nsec / 1000;
-    msec = t > n ? (int) ((t - n + 999) / 1000) : 0;
-  }
-
-  pollfd.fd = sd_journal_get_fd(j);
-  pollfd.events = sd_journal_get_events(j);
-  poll(&amp;pollfd, 1, msec);
-  return sd_journal_process(j);
-}</programlisting>
+    <programlisting><xi:include href="journal-iterate-poll.c" parse="text" /></programlisting>
   </refsect1>
 
   <refsect1>