Adding manpage generated with help2man.

Signed-off-by: Daniel Baumann <daniel@debian.org>

debian/control

@@ -7,6 +7,7 @@ Build-Depends:
  debhelper-compat (= 12),
  dh-python,
  git,
+ help2man,
  pylint,
  python3-all,
  python3-arrow,

debian/rules

@@ -10,7 +10,14 @@ override_dh_auto_test:
 	PYBUILD_SYSTEM=custom dh_auto_test
 
 execute_after_dh_auto_install:
-	# we don't want them in the package?
+	# manpage
+	mkdir -p debian/gitlint/usr/share/man/man1
+
+	PYTHONPATH=debian/gitlint/usr/lib/$$(py3versions -d)/dist-packages \
+		help2man --no-discard-stderr --name 'Git commit message linter' \
+		debian/gitlint/usr/bin/gitlint > debian/gitlint/usr/share/man/man1/gitlint.1
+
+	# removing unused files
 	rm -rf debian/gitlint/usr/lib/python*/dist-packages/qa
 
 execute_after_dh_fixperms: