add travis autobuild scripts (courtesy of EmuTOS project)

.travis/fix_travis_commit_range.sh

@@ -0,0 +1,35 @@
+# This script fragment must be sourced by the main script file
+# in order to define the FIXED_TRAVIS_COMMIT_RANGE variable
+# . .travis/fix_travis_commit_range.sh
+
+# TRAVIS_COMMIT_RANGE uses triple-dot syntax to specify which commits have
+# triggered the build. This is wrong. In case of forced push, the previous
+# commit is not an ancestor of the last commit, so it is not present in the
+# cloned repository. And also, the range contains unrelated commits.
+# https://docs.travis-ci.com/user/environment-variables/
+# https://git-scm.com/book/tr/v2/Git-Tools-Revision-Selection
+# https://github.com/travis-ci/travis-ci/issues/4596
+#
+# The solution is to use double-dot syntax instead.
+# In case of forced push, we can't know the previous commit. So we just use
+# the parent commit as previous one.
+
+echo TRAVIS_COMMIT_RANGE=$TRAVIS_COMMIT_RANGE
+
+PREVIOUS_COMMIT=$(echo $TRAVIS_COMMIT_RANGE | sed 's/\.\.\..*//')
+CURRENT_COMMIT=$TRAVIS_COMMIT
+
+if ! git merge-base --is-ancestor $PREVIOUS_COMMIT $CURRENT_COMMIT 2>/dev/null
+then
+  # Forced push: use parent commit as previous commit
+  PREVIOUS_COMMIT=$CURRENT_COMMIT~
+fi
+
+# Normalize commits
+PREVIOUS_COMMIT=$(git rev-parse --short $PREVIOUS_COMMIT)
+CURRENT_COMMIT=$(git rev-parse --short $CURRENT_COMMIT)
+
+export FIXED_TRAVIS_COMMIT_RANGE=$PREVIOUS_COMMIT..$CURRENT_COMMIT
+echo FIXED_TRAVIS_COMMIT_RANGE=$FIXED_TRAVIS_COMMIT_RANGE
+
+unset PREVIOUS_COMMIT CURRENT_COMMIT