Update pull request jenkinsfile to shortcut building docs

If docs are changed then docs "check" is run If only docs changed and
not other files, then only docs are built and other stages are
"fast-forwarded".

Also, remove docs from gitignore and from rebar.config.

3 files changed, 116 insertions, 11 deletions

diff --git a/.gitignore b/.gitignore
index 4a02f57ce..518ec7b19 100644
--- a/.gitignore
+++ b/.gitignore
@@ -50,7 +50,6 @@ src/couch/priv/couch_ejson_compare/couch_ejson_compare.d
 src/couch/priv/couch_js/**/*.d
 src/couch/priv/icu_driver/couch_icu_driver.d
 src/mango/src/mango_cursor_text.nocompile
-src/docs/
 src/ets_lru/
 src/excoveralls/
 src/fauxton/
diff --git a/build-aux/Jenkinsfile.pr b/build-aux/Jenkinsfile.pr
index db0d095d0..b64a3df6e 100644
--- a/build-aux/Jenkinsfile.pr
+++ b/build-aux/Jenkinsfile.pr
@@ -24,6 +24,9 @@ cd apache-couchdb-*
 make check || (make build-report && false)
 '''
 
+docs_changed = "git diff --name-only origin/${env.CHANGE_TARGET} | grep -q '^src/docs/'"
+other_changes = "git diff --name-only origin/${env.CHANGE_TARGET} | grep -q -v '^src/docs/'"
+
 pipeline {
 
   // no top-level agent; agents must be declared for each stage
@@ -61,7 +64,107 @@ pipeline {
 
   stages {
 
-    stage('erlfmt') {
+    stage('Setup Env') {
+      agent {
+          docker {
+              image "${DOCKER_IMAGE_BASE}-${LOW_ERLANG_VER}"
+              label 'docker'
+              args "${DOCKER_ARGS}"
+              registryUrl 'https://docker.io/'
+              registryCredentialsId 'dockerhub_creds'
+          }
+      }
+      options {
+          timeout(time: 10, unit: 'MINUTES')
+      }
+      steps {
+        script {
+            env.DOCS_CHANGED = '0'
+            env.ONLY_DOCS_CHANGED = '0'
+            if ( sh(returnStatus: true, script: docs_changed) == 0 ) {
+               env.DOCS_CHANGED = '1'
+               if (sh(returnStatus: true, script: other_changes) == 1) {
+                   env.ONLY_DOCS_CHANGED = '1'
+               }
+            }
+        }
+      }
+      post {
+        cleanup {
+          // UGH see https://issues.jenkins-ci.org/browse/JENKINS-41894
+          sh 'rm -rf ${WORKSPACE}/*'
+        }
+      }
+    } // stage 'Setup Environment'
+
+    stage('Docs Check') {
+      // Run docs `make check` stage if any docs changed
+      when {
+          beforeOptions true
+          expression { DOCS_CHANGED == '1' }
+      }
+      agent {
+          docker {
+              image "${DOCKER_IMAGE_BASE}-${LOW_ERLANG_VER}"
+              label 'docker'
+              args "${DOCKER_ARGS}"
+              registryUrl 'https://docker.io/'
+              registryCredentialsId 'dockerhub_creds'
+          }
+      }
+      options {
+        timeout(time: 15, unit: 'MINUTES')
+      }
+      steps {
+        sh '''
+          (cd src/docs && make check)
+        '''
+      }
+      post {
+        cleanup {
+          // UGH see https://issues.jenkins-ci.org/browse/JENKINS-41894
+          sh 'rm -rf ${WORKSPACE}/*'
+        }
+      }
+    } // stage Docs Check
+
+    stage('Build Docs') {
+      // Build docs separately if only docs changed. If there are other changes, docs are
+      // already built as part of `make dist`
+      when {
+          beforeOptions true
+          expression { ONLY_DOCS_CHANGED == '1' }
+      }
+      agent {
+          docker {
+              image "${DOCKER_IMAGE_BASE}-${LOW_ERLANG_VER}"
+              label 'docker'
+              args "${DOCKER_ARGS}"
+              registryUrl 'https://docker.io/'
+              registryCredentialsId 'dockerhub_creds'
+          }
+      }
+      options {
+          timeout(time: 30, unit: 'MINUTES')
+      }
+      steps {
+         sh '''
+           (cd src/docs && make html)
+         '''
+      }
+      post {
+        cleanup {
+          // UGH see https://issues.jenkins-ci.org/browse/JENKINS-41894
+          sh 'rm -rf ${WORKSPACE}/*'
+        }
+      }
+    } // stage Build Docs
+
+    stage('Erlfmt') {
+       when {
+          beforeOptions true
+          expression { ONLY_DOCS_CHANGED == '0' }
+       }
       agent {
         docker {
           image "${DOCKER_IMAGE_BASE}-${LOW_ERLANG_VER}"
@@ -76,7 +179,6 @@ pipeline {
       }
       steps {
         sh '''
-          set
           rm -rf apache-couchdb-*
           ./configure --skip-deps
           make erlfmt-check
@@ -88,10 +190,14 @@ pipeline {
           sh 'rm -rf ${WORKSPACE}/*'
         }
       }
-    } // stage erlfmt
+    } // stage Erlfmt
 
 
-    stage('Build Release Tarball') {
+    stage('Make Dist') {
+      when {
+          beforeOptions true
+          expression { ONLY_DOCS_CHANGED == '0' }
+      }
       agent {
         docker {
           image "${DOCKER_IMAGE_BASE}-${LOW_ERLANG_VER}"
@@ -106,7 +212,6 @@ pipeline {
       }
       steps {
         sh '''
-          set
           rm -rf apache-couchdb-*
           ./configure --spidermonkey-version 78
           make dist
@@ -122,14 +227,17 @@ pipeline {
           sh 'rm -rf ${WORKSPACE}/*'
         }
       }
-    } // stage Build Release Tarball
+    } // stage Make Dist
 
     // TODO Rework once Improved Docker Pipeline Engine is released
     // https://issues.jenkins-ci.org/browse/JENKINS-47962
     // https://issues.jenkins-ci.org/browse/JENKINS-48050
 
     stage('Make Check') {
-
+      when {
+          beforeOptions true
+          expression { ONLY_DOCS_CHANGED == '0' }
+      }
       matrix {
         axes {
           axis {
diff --git a/rebar.config.script b/rebar.config.script
index fc409c576..b0c2236bc 100644
--- a/rebar.config.script
+++ b/rebar.config.script
@@ -147,9 +147,7 @@ DepDescs = [
 {khash,            "khash",            {tag, "1.1.0"}},
 {snappy,           "snappy",           {tag, "CouchDB-1.0.8"}},
 
-%% Non-Erlang deps
-{docs,             {url, "https://github.com/apache/couchdb-documentation"},
-                   {tag, "3.2.1-1"}, [raw]},
+%% %% Non-Erlang deps
 {fauxton,          {url, "https://github.com/apache/couchdb-fauxton"},
                    {tag, "v1.2.8"}, [raw]},
 %% Third party deps