travis-ci: check AsciiDoc/AsciiDoctor stderr output

`make` does not necessarily fail with an error code if
Asciidoc/AsciiDoctor encounters problems. Anything written to stderr
might be a better indicator for problems.

Ensure that nothing is written to stderr during a documentation build.

The redirects do not work in `sh`, therefore the script uses `bash`.
This shouldn't be a problem as the script is only executed on TravisCI.

Signed-off-by: Lars Schneider <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: larsxschneider

ci/test-documentation.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env bash
 #
 # Perform sanity checks on documentation and build it.
 #
@@ -9,14 +9,17 @@ make check-builtins
 make check-docs
 
 # Build docs with AsciiDoc
-make --jobs=2 doc
+make --jobs=2 doc > >(tee stdout.log) 2> >(tee stderr.log >&2)
+! test -s stderr.log
 test -s Documentation/git.html
 test -s Documentation/git.xml
 test -s Documentation/git.1
 grep '<meta name="generator" content="AsciiDoc ' Documentation/git.html
 
 # Build docs with AsciiDoctor
 make clean
-make --jobs=2 USE_ASCIIDOCTOR=1 doc
+make --jobs=2 USE_ASCIIDOCTOR=1 doc > >(tee stdout.log) 2> >(tee stderr.log >&2)
+sed '/^GIT_VERSION = / d' stderr.log
+! test -s stderr.log
 test -s Documentation/git.html
 grep '<meta name="generator" content="Asciidoctor ' Documentation/git.html