chore(travis): verify conformance to commit message format

Added script that can be used to verify correctness of commit messages
in given range.

.travis.yml

@@ -8,6 +8,7 @@ os:
  - osx
 
 script:
+- if [[ "$TRAVIS_PULL_REQUEST" != "false" ]] && [[ "$TRAVIS_OS_NAME" == "linux" ]]; then bash ./verify-commit-messages.sh "$TRAVIS_COMMIT_RANGE" ; fi
 - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then bash ./.travis/build-ubuntu_14_04.sh; fi
 - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then bash ./osx/qTox-Mac-Deployer-ULTIMATE.sh -i ; fi
 - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then bash ./osx/qTox-Mac-Deployer-ULTIMATE.sh -b ; fi

verify-commit-messages.sh

@@ -0,0 +1,48 @@
+#!/bin/bash
+#
+#    Copyright © 2016 Zetok Zalbavar <zetok@openmailbox.org>
+#
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License as published by
+#    the Free Software Foundation, either version 3 of the License, or
+#    (at your option) any later version.
+#
+#    This program is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU General Public License for more details.
+#
+#    You should have received a copy of the GNU General Public License
+#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Script for verifying conformance to commit message format of commits in commit
+# range supplied.
+#
+# Scrpt fails (non-zero exit status) if commit messages don't conform.
+
+# usage:
+#   ./$script $commit_range
+#
+# $commit_range – in format `abdce..12345`
+
+ARG="$1"
+
+echo "" # ← formatting
+
+# Conform, /OR ELSE/.
+if git log --format=format:'%s' "$ARG" | \
+    grep -v -E '^(feat|fix|docs|style|refactor|perf|revert|test|chore)(\(.+\))?:.{1,68}$'
+then
+    echo ""
+    echo "Above ↑ commits don't conform to commit message format:"
+    echo "https://github.com/tux3/qTox/blob/master/CONTRIBUTING.md#commit-message-format"
+    echo ""
+    echo "Pls fix."
+    echo ""
+    echo "If you're not sure how to rewrite history, here's a helpful tutorial:"
+    echo "https://www.atlassian.com/git/tutorials/rewriting-history/git-commit--amend/"
+    echo ""
+    echo "If you're still not sure what to do, feel free to pop on IRC, or ask in PR comments for help :)"
+    # fail the build
+    exit 1
+fi