pg_rewind: Avoid need for empty callback test function.

Melanie suggested usage of
`declare -F <function_name> > /dev/null && <function_name>` in pg_rewind test.

-F will return only the name of the function and then the error code will be
non-zero if it is not defined and then by and-ing it with the function
definition alone, that function will only run in run_test if it is defined. So,
this helps to avoid coding empty functions if the test doesn't wish to have any
implementation for the same.
Co-authored-by: NMelanie Plageman <mplageman@pivotal.io>

src/bin/pg_rewind/sql/ao_rewind.sql

@@ -10,12 +10,6 @@ TESTNAME=ao_rewind
 
 . sql/config_test.sh
 
-# Nothing to do here
-function before_master
-{
-:
-}
-
 # Do an insert in master.
 function before_standby
 {

src/bin/pg_rewind/sql/basictest.sql

@@ -10,12 +10,6 @@ TESTNAME=basictest
 
 . sql/config_test.sh
 
-# Nothing to do here
-function before_master
-{
-:
-}
-
 # Do an insert in master.
 function before_standby
 {

src/bin/pg_rewind/sql/databases.sql

@@ -10,12 +10,6 @@ TESTNAME=databases
 
 . sql/config_test.sh
 
-# Nothing to do here
-function before_master
-{
-:
-}
-
 # Create a database in master.
 function before_standby
 {

src/bin/pg_rewind/sql/extrafiles.sql

@@ -12,12 +12,6 @@ TESTNAME=extrafiles
 
 . sql/config_test.sh
 
-# Nothing to do here
-function before_master
-{
-  :
-}
-
 # Create a subdir that will be present in both
 function before_standby
 {
@@ -43,11 +37,6 @@ function standby_following_master
   echo "in master3" > $TEST_MASTER/tst_master_dir/master_subdir/master_file3
 }
 
-function after_promotion
-{
-  :
-}
-
 # See what files and directories are present after rewind.
 function after_rewind
 {

src/bin/pg_rewind/sql/run_test.sh

@@ -49,13 +49,13 @@ EOF
 
 #### Now run the test-specific parts to initialize the master before setting
 echo "Master initialized."
-before_master
+declare -F before_master > /dev/null && before_master
 
 pg_ctl -w -D $TEST_MASTER start -o "$MASTER_PG_CTL_OPTIONS" >>$log_path 2>&1
 
 # up standby
 echo "Master running."
-before_standby
+declare -F before_standby > /dev/null && before_standby
 
 # Set up standby with necessary parameter
 rm -rf $TEST_STANDBY
@@ -76,7 +76,7 @@ pg_ctl -w -D $TEST_STANDBY start -o "$STANDBY_PG_CTL_OPTIONS" >>$log_path 2>&1
 #### Now run the test-specific parts to run after standby has been started
 # up standby
 echo "Standby initialized and running."
-standby_following_master
+declare -F standby_following_master > /dev/null && standby_following_master
 
 # sleep a bit to make sure the standby has caught up.
 sleep 1
@@ -95,7 +95,7 @@ wait_until_standby_is_promoted >>$log_path 2>&1
 
 #### Now run the test-specific parts to run after promotion
 echo "Standby promoted."
-after_promotion
+declare -F after_promotion > /dev/null && after_promotion
 
 # For some tests, we want to stop the master after standby promotion
 if [ "$STOP_MASTER_BEFORE_PROMOTE" != "true" ]; then
@@ -168,7 +168,7 @@ pg_ctl -w -D $TEST_MASTER promote >>$log_path 2>&1
 wait_until_master_is_promoted >>$log_path 2>&1
 echo "Master promoted."
 
-after_rewind
+declare -F after_rewind > /dev/null && after_rewind
 
 # Stop remaining servers
 pg_ctl stop -D $TEST_MASTER -m fast -w >>$log_path 2>&1

src/bin/pg_rewind/sql/simple_no_rewind_required.sql

@@ -11,24 +11,6 @@ STOP_MASTER_BEFORE_PROMOTE=true
 
 . sql/config_test.sh
 
-# Nothing to do here
-function before_master
-{
-:
-}
-
-# Nothing to do here
-function before_standby
-{
-:
-}
-
-# Nothing to do here
-function standby_following_master
-{
-:
-}
-
 # Run checkpoint to update Control File with new timeline ID
 function after_promotion
 {

src/bin/pg_rewind/sql/unclean_shutdown.sql

@@ -12,38 +12,10 @@ TESTNAME=unclean_shutdown
 
 MASTER_PG_CTL_STOP_MODE="immediate"
 
-# Nothing to do here
-function before_master
-{
-:
-}
-
-# Nothing to do here
-function before_standby
-{
-:
-}
-
-# Nothing to do here
-function standby_following_master
-{
-:
-}
-
-# Nothing to do here
-function after_promotion
-{
-:
-}
-
 # The old master was stopped with immediate mode which will cause unclean
 # shutdown and leave "in production" in the control file. At the beginning of
 # pg_rewind, a single-user mode postgres session should have been run to ensure
 # clean shutdown on the target instance.
-function after_rewind
-{
-:
-}
 
 # Run the test
 . sql/run_test.sh