(maint) Add task to check commit messages

Author: gimmyxd

.travis.yml

@@ -18,6 +18,8 @@ before_install:
 matrix:
   fast_finish: true
   include:
+  - rvm: 2.5.3
+    env: CHECK="commits"
   - rvm: 2.5.3
     env: CHECK="validate lint spec"
   - rvm: 2.5.3

Rakefile

@@ -41,3 +41,33 @@ task :gen_nodeset do
   end
   puts nodeset
 end
+
+desc "verify that commit messages match CONTRIBUTING.md requirements"
+task(:commits) do
+  # This rake task looks at the summary from every commit from this branch not
+  # in the branch targeted for a PR. This is accomplished by using the
+  # TRAVIS_COMMIT_RANGE environment variable, which is present in travis CI and
+  # populated with the range of commits the PR contains. If not available, this
+  # falls back to `master..HEAD` as a next best bet as `master` is unlikely to
+  # ever be absent.
+  commit_range = ENV['TRAVIS_COMMIT_RANGE'].nil? ? 'master..HEAD' : ENV['TRAVIS_COMMIT_RANGE'].sub(/\.\.\./, '..')
+  puts "Checking commits #{commit_range}"
+  %x{git log --no-merges --pretty=%s #{commit_range}}.each_line do |commit_summary|
+    # This regex tests for the currently supported commit summary tokens.
+    # The exception tries to explain it in more full.
+    if /^\((maint|packaging|doc|docs|modules-\d+)\)|revert/i.match(commit_summary).nil?
+      raise "\n\n\n\tThis commit summary didn't match CONTRIBUTING.md guidelines:\n" \
+        "\n\t\t#{commit_summary}\n" \
+        "\tThe commit summary (i.e. the first line of the commit message) should start with one of:\n"  \
+        "\t\t(MODULES-<digits>) # this is most common and should be a ticket at tickets.puppet.com\n" \
+        "\t\t(docs)\n" \
+        "\t\t(docs)(DOCUMENT-<digits>)\n" \
+        "\t\t(packaging)\n"
+        "\t\t(maint)\n" \
+        "\n\tThis test for the commit summary is case-insensitive.\n\n\n"
+    else
+      puts "#{commit_summary}"
+    end
+    puts "...passed"
+  end
+end