drm_hwcomposer: Fix check commit script to ignore case and extra spaces

Job 93709 [1] failed with missing committer sign-off. Ayan has their
committer string set to "Ayan kumar halder <ayan.halder@arm.com>", and
the Signed-off-by line on the commit was
"Signed-off-by: Ayan Kumar Halder <ayan.halder@arm.com>". So grep did
what we asked it to do and did not find the SoB since the case was
incorrect.

This patch changes to case-insensitive search and while we're at it,
trims excess whitespace from both the commit body and the
committer/author name.

Finally, I've improved the error message so it's hopefully more clear
why things fail in the future.

[1]- https://gitlab.freedesktop.org/ayan.halder/drm-hwcomposer/-/jobs/93709

Signed-off-by: Sean Paul <seanpaul@chromium.org>
diff --git a/.gitlab-ci-checkcommit.sh b/.gitlab-ci-checkcommit.sh
index fc8963a..d76baf7 100755
--- a/.gitlab-ci-checkcommit.sh
+++ b/.gitlab-ci-checkcommit.sh
@@ -4,6 +4,29 @@
 	printf "ERROR: %s\n" "$*" >&2
 }
 
+findtag() {
+	local commit_body tag person
+	commit_body=$1
+	tag=$2
+	person=$3
+
+	# trim duplicate spaces from commit body and person
+	match="$tag: $(echo $person | tr -s ' ')"
+
+	if [ -z "$(echo "$commit_body" | tr -s ' ' | grep -i "$match")" ]; then
+		echoerr "Tag is missing from commit body"
+		echoerr ""
+		echoerr "Looking for '"$match"' in: "
+		echoerr "-----------------------------------------------------"
+		echoerr "$commit_body"
+		echoerr "-----------------------------------------------------"
+		echoerr ""
+		return 0
+	fi
+
+	return 1
+}
+
 git fetch https://gitlab.freedesktop.org/drm-hwcomposer/drm-hwcomposer.git
 
 git log --pretty='%h' FETCH_HEAD..HEAD | while read h; do
@@ -16,15 +39,13 @@
 	commit_body=$(git show -s --pretty=%b "$h")
 
 	author=$(git show -s --format='%an <%ae>')
-	sob=$(echo "$commit_body" | grep "Signed-off-by: $author")
-	if [ -z "$sob" ] ; then
+	if findtag "$commit_body" "Signed-off-by" "$author"; then
 		echoerr "Author SoB tag is missing from commit $h"
 		exit 1
 	fi
 
 	committer=$(git show -s --format='%cn <%ce>')
-	sob=$(echo "$commit_body" | grep "Signed-off-by: $committer")
-	if [ -z "$sob" ] ; then
+	if findtag "$commit_body" "Signed-off-by" "$committer"; then
 		echoerr "Committer SoB tag is missing from commit $h"
 		exit 1
 	fi