[Issue #169] Documentation update

Author: gsmolk

doc/pgprobackup.xml

@@ -2242,6 +2242,13 @@ BACKUP INSTANCE 'node'
                 <literal>MERGING</literal> — the backup is being merged.
               </para>
             </listitem>
+            <listitem>
+              <para>
+                <literal>MERGED</literal> — the backup data files were
+                successfully merged, but its metadata is in the process
+                of been updated. Only full backup can have this status.
+              </para>
+            </listitem>
             <listitem>
               <para>
                 <literal>DELETING</literal> — the backup files are being deleted.
@@ -3146,7 +3153,9 @@ pg_probackup merge -B <replaceable>backup_dir</replaceable> --instance <replacea
     <para>
       This command merges the specified incremental backup to its
       parent full backup, together with all incremental backups
-      between them. Once the merge is complete, the incremental
+      between them. If the specified backup ID belong to the full backup,
+      then it will be merged with the closest incremental backup.
+      Once the merge is complete, the incremental
       backups are removed as redundant. Thus, the merge operation is
       virtually equivalent to retaking a full backup and removing all
       the outdated backups, but it allows to save much time,
@@ -3165,7 +3174,8 @@ pg_probackup show -B <replaceable>backup_dir</replaceable> --instance <replaceab
 </programlisting>
     <para>
       If the merge is still in progress, the backup status is
-      displayed as <literal>MERGING</literal>. The merge is idempotent, so you can
+      displayed as <literal>MERGING</literal> or, at the final stage,
+      <literal>MERGED</literal>. The merge is idempotent, so you can
       restart the merge if it was interrupted.
     </para>
   </refsect2>
@@ -3404,6 +3414,7 @@ pg_probackup backup -B <replaceable>backup_dir</replaceable> -b <replaceable>bac
 [--no-validate] [--skip-block-validation]
 [-w --no-password] [-W --password]
 [--archive-timeout=<replaceable>timeout</replaceable>] [--external-dirs=<replaceable>external_directory_path</replaceable>]
+[--no-sync]
 [<replaceable>connection_options</replaceable>] [<replaceable>compression_options</replaceable>] [<replaceable>remote_options</replaceable>]
 [<replaceable>retention_options</replaceable>] [<replaceable>pinning_options</replaceable>] [<replaceable>logging_options</replaceable>]
 </programlisting>
@@ -3556,6 +3567,18 @@ pg_probackup backup -B <replaceable>backup_dir</replaceable> -b <replaceable>bac
       </para>
       </listitem>
       </varlistentry>
+
+      <varlistentry>
+<term><option>--no-sync</option></term>
+      <listitem>
+      <para>
+        Do not sync backed up files to disk. You can use this flag to speed
+        up backup process. Using this flag can result in data
+        corruption in case of operating system or hardware crash.
+        Corruption can be detected by backup validation.
+      </para>
+      </listitem>
+      </varlistentry>
       </variablelist>
       </para>
 
@@ -3583,7 +3606,7 @@ pg_probackup restore -B <replaceable>backup_dir</replaceable> --instance <replac
 [-j <replaceable>num_threads</replaceable>] [--progress]
 [-T <replaceable>OLDDIR</replaceable>=<replaceable>NEWDIR</replaceable>] [--external-mapping=<replaceable>OLDDIR</replaceable>=<replaceable>NEWDIR</replaceable>] [--skip-external-dirs]
 [-R | --restore-as-replica] [--no-validate] [--skip-block-validation] [--force]
-[--restore-command=<replaceable>cmdline</replaceable>]
+[--restore-command=<replaceable>cmdline</replaceable>] [--no-sync]
 [<replaceable>recovery_target_options</replaceable>] [<replaceable>logging_options</replaceable>] [<replaceable>remote_options</replaceable>]
 [<replaceable>partial_restore_options</replaceable>] [<replaceable>remote_wal_archive_options</replaceable>]
 </programlisting>
@@ -3705,6 +3728,17 @@ pg_probackup restore -B <replaceable>backup_dir</replaceable> --instance <replac
       </para>
       </listitem>
       </varlistentry>
+
+      <varlistentry>
+<term><option>--no-sync</option></term>
+      <listitem>
+      <para>
+        Do not sync restored files to disk. You can use this flag to speed
+        up restore process. Using this flag can result in data
+        corruption in case of operating system or hardware crash.
+      </para>
+      </listitem>
+      </varlistentry>
     </variablelist>
     </para>
       <para>
@@ -3831,7 +3865,9 @@ pg_probackup merge -B <replaceable>backup_dir</replaceable> --instance <replacea
       <para>
         Merges the specified incremental backup to its parent full
         backup, together with all incremental backups between them, if
-        any. As a result, the full backup takes in all the merged
+        any. If the specified backup ID belong to the full backup,
+        then it will be merged with the closest incremental backup.
+        As a result, the full backup takes in all the merged
         data, and the incremental backups are removed as redundant.
       </para>
       <para>