Cirrus: Reveal magic, parallel system-testing

Previously, several magic strings were in place to affect cirrus-ci
operations.  Two were buried within scripts.  One to optionally
execute system-tests within a PR. Another to avoid re-building
cache-images upon every merge.

Move these magic strings out into the open, buy locating their
logic up-front in the ``.cirrus.yml`` file.  This improves
readability and reduces surprise/astonishment at runtime.

Signed-off-by: Chris Evich <cevich@redhat.com>

contrib/cirrus/build_vm_images.sh

@@ -22,8 +22,6 @@ SCRIPT_BASE $SCRIPT_BASE
 PACKER_BASE $PACKER_BASE
 "
 
-require_regex '\*\*\*\s*CIRRUS:\s*REBUILD\s*IMAGES\s*\*\*\*' 'Not re-building VM images'
-
 show_env_vars
 
 # Everything here is running on the 'image-builder-image' GCE image

contrib/cirrus/lib.sh

@@ -120,23 +120,6 @@ cdsudo() {
     sudo --preserve-env=GOPATH --non-interactive bash -c "$CMD"
 }
 
-# Skip a build if $1 does not match in the PR Title/Description with message $2
-require_regex() {
-    req_env_var "
-        CIRRUS_CHANGE_MESSAGE $CIRRUS_CHANGE_MESSAGE
-        1 $1
-        2 $2
-    "
-    regex="$1"
-    msg="$2"
-    if ! echo "$CIRRUS_CHANGE_MESSAGE" | egrep -q "$regex"
-    then
-        echo "***** The PR Title/Description did not match the regular expression: $MAGIC_RE"
-        echo "***** $msg"
-        exit 0
-    fi
-}
-
 # Helper/wrapper script to only show stderr/stdout on non-zero exit
 install_ooe() {
     req_env_var "SCRIPT_BASE $SCRIPT_BASE"

contrib/cirrus/optional_system_test.sh

@@ -3,14 +3,6 @@
 set -e
 source $(dirname $0)/lib.sh
 
-MAGIC_RE='\*\*\*\s*CIRRUS:\s*SYSTEM\s*TEST\s*\*\*\*'
-if ! echo "$CIRRUS_CHANGE_MESSAGE" | egrep -q "$MAGIC_RE"
-then
-    echo "Skipping system-testing because PR title or description"
-    echo "does not match regular expression: $MAGIC_RE"
-    exit 0
-fi
-
 req_env_var "
 GOSRC $GOSRC
 OS_RELEASE_ID $OS_RELEASE_ID