travis-ci: build documentation

Build documentation as separate Travis CI job to check for
documentation errors.

Signed-off-by: Lars Schneider <larsxschneider@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

.travis.yml

@@ -32,6 +32,21 @@ env:
     # t9816 occasionally fails with "TAP out of sequence errors" on Travis CI OS X
     - GIT_SKIP_TESTS="t9810 t9816"
 
+matrix:
+  include:
+    - env: Documentation
+      os: linux
+      compiler: clang
+      addons:
+        apt:
+          packages:
+          - asciidoc
+          - xmlto
+      before_install:
+      before_script:
+      script: ci/test-documentation.sh
+      after_failure:
+
 before_install:
   - >
     case "${TRAVIS_OS_NAME:-linux}" in

ci/test-documentation.sh

@@ -0,0 +1,14 @@
+#!/bin/sh
+#
+# Perform sanity checks on documentation and build it.
+#
+
+set -e
+
+make check-builtins
+make check-docs
+make doc
+
+test -s Documentation/git.html
+test -s Documentation/git.xml
+test -s Documentation/git.1