improve atomic deployments (#55)

- use paths for versioning
   - use major.minor.patch-commits_since_version_source
   - remove purge instructions as it is no longer required
   - add instruction to switch between versions

Pros
 1. 100% atomic deployments. Content won’t be available till the big-bang
    moment in which the origin’s path gets updated. Purge or content
    expiration doesn’t affect what Azure CDN serves leaving you in full
    control when new content starts being served.
 2. better content organization and visualization
 3. don't have to wait for cache to expire before Azure CDN begins to
    serve a new version and it doesn’t require to execute a purge
    action (cache invalidation)
 4. enhanceed control over managing the content that Azure CDN serves
    - it is possible to easily clean up the container enabling use cases
      like history max level (e.g. keep last 3 most recent versions)
    - it is just matter of target another container folder to rollback to
      a previous version
    - it allows SxS versions enabling more sophisticated use cases like
      previewing new website versions before they are live and many other
      scenarios (support older versions, variations, etc.)

Cons
1. if some content was being downloaded and newer version just kicked-in, user
   might face some 404.
2. more space might be required, same content is now duplicated on every folder

solved: #114210

Author: Fernando Antivero

src/ClientApp/azure-pipelines.yml

@@ -39,7 +39,9 @@ stages:
 
     - script: |
         cd $(Build.SourcesDirectory)
-        echo $(docker run --rm -v "$(pwd):/repo" gittools/gitversion:5.0.1-linux-netcoreapp2.1 /repo | grep -oP '(?<="MajorMinorPatch":")[^"]*') > src/ClientApp/public/version.txt
+        echo $(docker run --rm -v "$(pwd):/repo" gittools/gitversion:5.0.1-linux-netcoreapp2.1 /repo) > .gitversion
+        echo $(cat .gitversion | grep -oP '(?<="MajorMinorPatch":")[^"]*') > src/ClientApp/public/version.txt
+        echo $(cat .gitversion | grep -oP '(?<="FullSemVer":")[^"]*' | sed -e "s/\+/-/g") > src/ClientApp/public/semver.txt
       displayName: 'bump version'
 
     - task: PublishBuildArtifacts@1
@@ -61,6 +63,7 @@ stages:
           steps:
           - script: |
               echo '##vso[task.setvariable variable=releaseVersion]'$(cat "$(Pipeline.Workspace)/drop/version.txt")
+              echo '##vso[task.setvariable variable=releaseSemVer]'$(cat "$(Pipeline.Workspace)/drop/semver.txt")
             displayName: 'set release version'
             name: setVarReleaseVersion
 
@@ -75,15 +78,17 @@ stages:
 
           - script: |
               az login --service-principal -u $(azureArmClientId) -p $(azureArmClientSecret) --tenant $(azureArmTenantId)
-              az storage blob upload-batch -s "$(Pipeline.Workspace)/drop" --destination \$web --account-name $(azureStorageAccountName)
-              az cdn endpoint purge --resource-group $(azureResourceGroup) --profile-name $(azureCdnName) --name $(azureCdnName) --content-paths '/' '/index.html' '/404.html' '/version.txt'
+              # upload content to container versioned folder
+              az storage blob upload-batch -s "$(Pipeline.Workspace)/drop" --destination "\$web\$(releaseSemVer)" --account-name $(azureStorageAccountName)
+              # target new version
+              az cdn endpoint update --resource-group $(azureResourceGroup) --profile-name $(azureCdnName) --name $(azureCdnName) --origin-path '/$(releaseSemVer)'
               AZURE_CDN_ENDPOINT_HOSTNAME=$(az cdn endpoint show --resource-group $(azureResourceGroup) --name $(azureCdnName) --profile-name $(azureCdnName) --query hostName -o tsv)
               echo "Azure CDN endpooint host ${AZURE_CDN_ENDPOINT_HOSTNAME}"
               echo '##vso[task.setvariable variable=azureCndEndpointHost]'$AZURE_CDN_ENDPOINT_HOSTNAME
             displayName: 'upload to Azure Storage static website hosting and purge Azure CDN endpoint'
           
           - script: |
-              liveVersion=$(curl --fail --silent "https://$(azureCndEndpointHost)/version.txt")
-              [[ $liveVersion == $(releaseVersion) ]] && echo -e "\033[1;32m## [Passed] website validation Ok: $liveVersion is live now\033[0m" || >&2 echo -e "\033[0;31m## [Fail] website validation Fail: expected $(releaseVersion) - actual $liveVersion\033[0m"
+              liveVersion=$(curl --fail --silent "https://$(azureCndEndpointHost)/semver.txt")
+              [[ $liveVersion == $(releaseSemVer) ]] && echo -e "\033[1;32m## [Passed] website validation Ok: $liveVersion is live now\033[0m" || >&2 echo -e "\033[0;31m## [Fail] website validation Fail: expected $(releaseSemVer) - actual $liveVersion\033[0m"
             displayName: 'validate website version'
             failOnStderr: true