Fix conditions for builds in CI, and document in comments

.travis.yml

@@ -34,24 +34,24 @@ addons:
     packages:
       - zmq
 
-# Docs are only built and deployed in "cron" builds - so only prepare that when needed
+# Doc building tools are needed on linux with stable rust
 before_install:
   - make no-book-config
   - |
-    if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then
+    if [[ "$TRAVIS_OS_NAME" == "linux" && "$TRAVIS_RUST_VERSION" == "stable" ]]; then
       make book-config
     fi
 
-# Docs are only built and deployed in "cron" builds on linux with rust stable
+# Docs are only built on linux with stable rust
 script:
   - |
-    if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then
+    if [[ "$TRAVIS_OS_NAME" == "linux" && "$TRAVIS_RUST_VERSION" == "stable" ]]; then
       travis_wait 50 make clippy build test docs
     else
       travis_wait 50 make clippy test
     fi
 
-# Docs are only built and deployed in "cron" builds on linux with rust stable
+# Docs are only on linux builds of master branch with stable rust
 deploy:
   provider: pages
   skip_cleanup: true
@@ -67,6 +67,7 @@ notifications:
   email:
   - [email protected]
 
+# avoid measuring coverage on CRON builds, only measure on non-CRON linux builds with stable rust
 after_success: |
   if [[ "$TRAVIS_OS_NAME" == "linux" && "$TRAVIS_RUST_VERSION" == "stable" && "$TRAVIS_EVENT_TYPE" != "cron" ]]; then
     FLOW_LIB_PATH=$TRAVIS_BUILD_DIR,$TRAVIS_BUILD_DIR/flowr/src/lib make coverage