Cirrus: Add golang code consistency check script

Depends on #15893

Fixes: #15913

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

contrib/cirrus/check_go_changes.sh

@@ -0,0 +1,53 @@
+#!/bin/bash
+
+set -eo pipefail
+
+# This script is intended to confirm new go code conforms to certain
+# conventions and/or does not introduce use of old/deprecated packages
+# or functions.  It needs to run in the Cirrus CI environment, on behalf
+# of PRs, via runner.sh.  This ensures a consistent and predictable
+# environment not easily reproduced by a `Makefile`.
+
+# shellcheck source=contrib/cirrus/lib.sh
+source $(dirname $0)/lib.sh
+
+check_msg() {
+    msg "#####"  # Cirrus-CI logs automatically squash empty lines
+    msg "##### $1"  # Complains if $1 is empty
+}
+
+# First arg is check description, second is regex to search $diffs for.
+check_diffs() {
+    local check regex
+    check="$1"
+    regex="$2"
+    check_msg "Confirming changes have no $check"
+    req_env_vars check regex diffs
+    if egrep -q "$regex"<<<"$diffs"; then
+        # Show 5 context lines before/after as compromise for script simplicity
+        die "Found $check:
+$(egrep -B 5 -A 5 "$regex"<<<"$diffs")"
+    fi
+}
+
+if [[ -n "$CIRRUS_TAG" ]] || ! req_env_vars CIRRUS_CHANGE_IN_REPO CIRRUS_PR DEST_BRANCH
+then
+    warn "Skipping: Golang code checks cannot run in this context"
+    exit 0
+fi
+
+base=$(git merge-base $DEST_BRANCH $CIRRUS_CHANGE_IN_REPO)
+diffs=$(git diff $base $CIRRUS_CHANGE_IN_REPO -- '*.go' ':^vendor/')
+
+if [[ -z "$diffs" ]]; then
+    check_msg "There are no golang diffs to check between $base...$CIRRUS_CHANGE_IN_REPO"
+    exit 0
+fi
+
+check_diffs \
+    "use of deprecated ioutil vs recommended io or os packages." \
+    "^(\\+[^#]+io/ioutil)|(\\+.+ioutil\\..+)"
+
+check_diffs \
+    "use of os.IsNotExists(err) vs recommended errors.Is(err, os.ErrNotExist)" \
+    "^\\+[^#]*os\\.IsNotExists\\("

contrib/cirrus/runner.sh

@@ -233,25 +233,7 @@ function _run_consistency() {
     SUGGESTION="run 'make generate-bindings' and commit all changes" ./hack/tree_status.sh
     make completions
     SUGGESTION="run 'make completions' and commit all changes" ./hack/tree_status.sh
-
-    if  [[ -z "$CIRRUS_TAG" ]] && \
-        req_env_vars CIRRUS_CHANGE_IN_REPO CIRRUS_PR DEST_BRANCH
-    then
-        local base diffs regex i
-        # Prevent this check from detecting itself
-        i=i
-        msg "#####"
-        msg "Verifying no change adds new calls to ${i}o/${i}outil."
-        base=$(git merge-base $DEST_BRANCH $CIRRUS_CHANGE_IN_REPO)
-        diffs=$(git diff $base $CIRRUS_CHANGE_IN_REPO -- '*.go' ':^vendor/')
-        regex=$(echo -e "^(\\+.+${i}o/${i}outil)|(\\+.+${i}outil\\..+)")
-        if egrep -q "$regex"<<<"$diffs"; then
-            die "Found attempted use of deprecated ${i}outils:
-$(egrep -B 5 -A 5 "$regex"<<<"$diffs")"
-        fi
-    else
-        msg "Skipping check for ${i}o/${i}outil addition."
-    fi
+    $SCRIPT_BASE/check_go_changes.sh
 }
 
 function _run_build() {