Linkcheck only changed files (except for cron jobs)

.travis.yml

@@ -12,7 +12,7 @@ before_install:
 install:
 - source ~/.cargo/env || true
 - cargo install mdbook --version '^0.4.3'
-- cargo install mdbook-linkcheck --version '^0.7.0'
+- cargo install mdbook-linkcheck --git https://github.com/Michael-F-Bryan/mdbook-linkcheck --rev 14441d77646d58cea8ffc32fde9ea33b2bedb1a2
 script:
 - git checkout -b ci
 - git rebase origin/master

book.toml

@@ -14,6 +14,7 @@ enable = true
 level = 0
 
 [output.linkcheck]
+command = "../../ci/linkcheck.sh"
 follow-web-links = true
 exclude = [ "crates\\.io", "gcc\\.godbolt\\.org", "youtube\\.com", "youtu\\.be", "dl\\.acm\\.org", "cs\\.bgu\\.ac\\.il", "www\\.amazon\\.com", "www\\.rustaceans\\.org" ]
 cache-timeout = 86400

ci/linkcheck.sh

@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+
+set -ev
+set -o pipefail
+
+# https://docs.travis-ci.com/user/environment-variables/#default-environment-variables
+if [ "$TRAVIS_EVENT_TYPE" = "cron" ] ; then # running in cron job
+  FLAGS=""
+
+  echo "Doing full link check."
+elif [ "$CI" = "true" ] ; then # running in PR CI build
+  if [ -z "$TRAVIS_COMMIT_RANGE" ]; then
+    echo "error: unexpected state: TRAVIS_COMMIT_RANGE must be non-empty in CI"
+    exit 1
+  fi
+
+  CHANGED_FILES=$(git diff --name-only $TRAVIS_COMMIT_RANGE | tr '\n' ' ')
+  FLAGS="-f $CHANGED_FILES"
+
+  echo "Checking files changed in $TRAVIS_COMMIT_RANGE: $CHANGED_FILES"
+else # running locally
+  COMMIT_RANGE=master...
+  CHANGED_FILES=$(git diff --name-only $COMMIT_RANGE | tr '\n' ' ')
+  FLAGS="-f $CHANGED_FILES"
+
+  echo "Checking files changed in $COMMIT_RANGE: $CHANGED_FILES"
+fi
+
+exec mdbook-linkcheck $FLAGS -- $TRAVIS_BUILD_DIR