man: Update dpkg --log documentation

Add missing actions, and describe the startup messages.

Closes: #773398

debian/changelog

@@ -5,6 +5,8 @@ dpkg (1.18.0) UNRELEASED; urgency=low
     Closes: #768842
   * Document versioned Provides in deb-control(5).
   * Document the version when dpkg-deb --raw-extract got introduced.
+  * Document dpkg --log format, add missing actions and describe the startup
+    messages. Closes: #773398
 
  -- Guillem Jover <guillem@debian.org>  Tue, 09 Dec 2014 23:53:18 +0100
 

man/dpkg.1

@@ -702,11 +702,16 @@ multiple times. The output format used is the same as in \fB\-\-status\-fd.
 Log status change updates and actions to \fIfilename\fP, instead of
 the default \fI/var/log/dpkg.log\fP. If this option is given multiple
 times, the last filename is used. Log messages are of the form
+`YYYY-MM-DD HH:MM:SS startup \fItype\fP \fIcommand\fP' for each dpkg
+invocation where \fItype\fP is \fBarchives\fP (with a \fIcommand\fP of
+\fBunpack\fP or \fBinstall\fP) or \fBpackages\fP (with a \fIcommand\fP of
+\fBconfigure\fP, \fBtriggers\-only\fP, \fBremove\fP or \fBpurge\fP);
 `YYYY-MM-DD HH:MM:SS status \fIstate\fP \fIpkg\fP \fIinstalled-version\fP'
 for status change updates;
 `YYYY-MM-DD HH:MM:SS \fIaction\fP \fIpkg\fP \fIinstalled-version\fP
 \fIavailable-version\fP' for actions where \fIaction\fP is one of
-\fBinstall\fP, \fBupgrade\fP, \fBremove\fP, \fBpurge\fP; and
+\fBinstall\fP, \fBupgrade\fP, \fBconfigure\fP, \fBtrigproc\fP,
+\fBdisappear\fP, \fBremove\fP or \fBpurge\fP; and
 `YYYY-MM-DD HH:MM:SS conffile \fIfilename\fP \fIdecision\fP' for conffile
 changes where \fIdecision\fP is either \fBinstall\fP or \fBkeep\fP.
 .TP