diff --git a/.travis.yml b/.travis.yml
index f62aa14901..34423e84b4 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -31,7 +31,9 @@ cache:
 services: mongodb
 
 before_install:
+    # Matrix lines for intermediate PHP versions are skipped for pull requests
     - if [[ ! $deps && ! $TRAVIS_PHP_VERSION = ${MIN_PHP%.*} && $TRAVIS_PHP_VERSION != hhvm && $TRAVIS_PULL_REQUEST != false ]]; then deps=skip; fi;
+    # A sigchild-enabled-PHP is used to test the Process component on the lowest PHP matrix line
     - if [[ ! $deps && $TRAVIS_PHP_VERSION = ${MIN_PHP%.*} && ! -d php-$MIN_PHP/sapi ]]; then wget http://museum.php.net/php5/php-$MIN_PHP.tar.bz2 -O - | tar -xj; (cd php-$MIN_PHP; ./configure --enable-sigchild --enable-pcntl; make -j2); fi;
     - if [[ $TRAVIS_PHP_VERSION != hhvm ]]; then INI_FILE=~/.phpenv/versions/$(phpenv version-name)/etc/conf.d/travis.ini; else INI_FILE=/etc/hhvm/php.ini; fi;
     - echo memory_limit = -1 >> $INI_FILE
@@ -50,9 +52,12 @@ before_install:
 
 install:
     - if [[ $deps != skip ]]; then COMPONENTS=$(find src/Symfony -mindepth 3 -type f -name phpunit.xml.dist -printf '%h\n'); fi;
+    # Create local composer packages for each patched components and reference them in composer.json files when cross-testing components
     - if [[ $deps != skip && $deps ]]; then php .travis.php $TRAVIS_COMMIT_RANGE $TRAVIS_BRANCH $COMPONENTS; fi;
+    # For the master branch when deps=high, the version before master is checked out and tested with the locally patched components
     - if [[ $deps = high && $TRAVIS_BRANCH = master ]]; then SYMFONY_VERSION=$(git ls-remote --heads | grep -o '/[1-9].*' | tail -n 1 | sed s/.//); else SYMFONY_VERSION=$(cat composer.json | grep '^ *"dev-master". *"[1-9]' | grep -o '[0-9.]*'); fi;
     - if [[ $deps = high && $TRAVIS_BRANCH = master ]]; then git fetch origin $SYMFONY_VERSION; git checkout -m FETCH_HEAD; COMPONENTS=$(find src/Symfony -mindepth 3 -type f -name phpunit.xml.dist -printf '%h\n'); fi;
+    # Legacy tests are skipped when deps=high and when the current branch version has not the same major version number than the next one
     - if [[ $deps = high && ${SYMFONY_VERSION%.*} != $(git show $(git ls-remote --heads | grep -FA1 /$SYMFONY_VERSION | tail -n 1):composer.json | grep '^ *"dev-master". *"[1-9]' | grep -o '[0-9]*' | head -n 1) ]]; then LEGACY=,legacy; fi;
     - export COMPOSER_ROOT_VERSION=$SYMFONY_VERSION.x-dev;
     - if [[ ! $deps ]]; then composer update --prefer-dist; else export SYMFONY_DEPRECATIONS_HELPER=weak; fi;