setup: enhance --new-systemd-unit

Do not left created dropin directory in case of some initdb
failure, or so.  This allow user run the same --new-systemd-unit
repeatedly without changing the command-line.

* postgresql-setup.in (exit_handler): New exit callback wrapper.
($cleanup_dropin): Code to be executed to clean drop-in directory.
(generate_systemd_dropin): Fill $cleanup_dropin callback.
(initdb): Clean $cleanup_dropin in case of successful initdb.
This is not needed for upgrade() because we never create drop-ins
there.

* NEWS: Document changes.

Author: praiskup

NEWS

@@ -1,5 +1,10 @@
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
+New in 3.1 version
+
+* The --new-systemd-unit option now cleans the recently created drop-in
+  directory if something goes wrong.
+
 Bugfixes in 3.2 version
 
 * Fix regression of setting the default pgdata variable for non-default

postgresql-setup.in

@@ -168,6 +168,7 @@ initdb()
     info $"Initializing database in '$pgdata'$port_info"
     if check_not_initialized && perform_initdb; then
         info $"Initialized, logs are in ${initdb_log}"
+        cleanup_dropin=
     else
         error $"Initializing database failed, possibly see $initdb_log"
         script_result=1
@@ -324,6 +325,8 @@ generate_systemd_dropin()
     mkdir -p "$dropindir" \
         || die "Can not create '$dropindir'"
 
+    cleanup_dropin="rm -rf \"$dropindir\""
+
     cat <<EOF > "$dropin" || die "Can not write to '$dropin'"
 [Service]
 Environment=PGDATA=$pgdata
@@ -502,6 +505,16 @@ service_configuration()
     test -n "$envfile_pgport" && set_var "$portvar" "$envfile_pgport"
 }
 
+cleanup_dropin=
+exit_handler()
+{
+    test -n "$cleanup_dropin" && {
+        info "cleaning up created dropin directory"
+        eval "$cleanup_dropin"
+    }
+}
+
+trap exit_handler 0
 
 # <Compat>
 # Alow users to use the old style arguments like