[gnome-contacts/wip/nielsdg/commit-cehcks] ci: Do some basic checks on the commit message

[Niels De Graef <nielsdg src gnome org>]

commit d64996a91730713fd91703934ef1ac94c54f05dd
Author: Niels De Graef <nielsdegraef gmail com>
Date:   Sun Dec 6 15:09:58 2020 +0100

    ci: Do some basic checks on the commit message

 .gitlab-ci.yml             | 13 +++++++++++
 .gitlab/ci/commit-check.sh | 55 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index c78259fb..61230e67 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -18,6 +18,19 @@ style-check:
     paths:
       - "style-check-junit-report.xml"
 
+commit-check:
+  stage: review
+  script:
+    - ./.gitlab/ci/commit-check.sh
+  artifacts:
+    expire_in: 1 week
+    name: "style-check-junit-report"
+    when: always
+    reports:
+      junit: commit-check-junit-report.xml
+    paths:
+      - "commit-check-junit-report.xml"
+    allow_failure: true
 
 flatpak:
   image: registry.gitlab.gnome.org/gnome/gnome-runtime-images/gnome:master
diff --git a/.gitlab/ci/commit-check.sh b/.gitlab/ci/commit-check.sh
new file mode 100755
index 00000000..81765035
--- /dev/null
+++ b/.gitlab/ci/commit-check.sh
@@ -0,0 +1,55 @@
+#!/usr/bin/env bash
+#
+# commit-check.sh: Performs some basic checks on commit messages
+#
+# For general recommendations, see https://wiki.gnome.org/Git/CommitMessages
+
+# Source the JUnit helpers
+scriptdir="$(dirname "$BASH_SOURCE")"
+source "$scriptdir/junit-report.sh"
+
+target_branch="${CI_MERGE_REQUEST_TARGET_BRANCH_NAME:-${CI_DEFAULT_BRANCH}}"
+
+# Get the list of commits (hashes) in this branch
+git fetch "$CI_MERGE_REQUEST_PROJECT_URL.git" "$target_branch"
+branch_point="$(git merge-base HEAD FETCH_HEAD)"
+commits="$(git log --format='format:%H' $branch_point..$CI_COMMIT_SHA)"
+
+if [[ -z "$commits" ]]; then
+  echo "Commit range empty" >&2
+  exit 1
+fi
+
+for commit in $commits; do
+  commit_msg="$(git show -s --format='format:%B' $commit)"
+
+  # Note: this might seem a bit strict, but remember that we allow this to fail
+  # in the CI pipeline (although it will give warnings).
+  TESTNAME="Lines shouldn't be too long"
+  MAX_LENGTH=75
+  too_long_lines="$(echo "$commit_msg" | grep ".\{$(( MAX_LENGTH + 1 ))\}" )"
+  if [[ -z "$too_long_lines" ]]; then
+    append_passed_test_case "$TESTNAME"
+  else
+    append_failed_test_case "$TESTNAME" \
+      "Commit $commit: Some lines are over $MAX_LENGTH characters:"$'\n\n'"$too_long_lines"
+  fi
+
+
+  # Needed to have nicely working shortlog
+  TESTNAME="2nd line should be empty"
+  if [[ "$(echo "$commit_msg" | wc -l)" -le 1 ]]; then
+    # Commit is just one line long, so we're ok
+    append_passed_test_case "$TESTNAME"
+  elif [[ -z "$(echo "$commit_msg" | sed -n "2p")" ]]; then
+    # 2nd line is empty
+    append_passed_test_case "$TESTNAME"
+  else
+    append_failed_test_case "$TESTNAME" \
+      "Commit $commit: Second line is not empty"
+  fi
+done
+
+# Generate report
+generate_junit_report "$CI_JOB_NAME-junit-report.xml" "$CI_JOB_NAME"
+check_junit_report "$CI_JOB_NAME-junit-report.xml"