license: removes copyright year and uses SPDX ID

As a small project, we have to conserve resources and not sign up for work that isn't required. I've recently realized many [commercial](https://github.com/hashicorp/consul/blob/main/command/cli/cli.go#L1-L2) and/or [CNCF projects](https://github.com/open-telemetry/opentelemetry-java/blob/main/api/all/src/main/java/io/opentelemetry/api/trace/Tracer.java#L1-L4) both use SPDX IDs and also don't bother with copyright year. If their legal team is ok with this, surely a volunteer team without access to one should be, too!

Doing so accomplishes the following, all of which help volunteers:
* significantly increases readability of files, particularly small ones
* removes beginning of year maintenance, which cause a lot of FUD last year. IIRC some deployment failed and hours were spent in spite of docs.
* eliminates the need to do a full source check out, just to satisfy the license plugin. This means we can use actions/checkout defaults.

Signed-off-by: Adrian Cole <adrian@tetrate.io>

.github/CONTRIBUTING.md

@@ -17,17 +17,8 @@ If you are adding a new file it should have a header like below. This
 can be automatically added by running `./mvnw com.mycila:license-maven-plugin:format`.
 
 ```
-/**
- * Copyright 2019 The OpenZipkin Authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
- * in compliance with the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software distributed under the License
- * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
- * or implied. See the License for the specific language governing permissions and limitations under
- * the License.
+/*
+ * Copyright The OpenZipkin Authors
+ * SPDX-License-Identifier: Apache-2.0
  */
  ```

.github/workflows/create_release.yml

@@ -18,7 +18,6 @@ jobs:
           # Prevent use of implicit GitHub Actions read-only GITHUB_TOKEN
           # because maven-release-plugin pushes commits to master.
           token: ${{ secrets.GH_TOKEN }}
-          fetch-depth: 1  # license check is skipped, so we don't need history
       - name: Setup java
         uses: actions/setup-java@v4
         with:

.github/workflows/deploy.yml

@@ -23,7 +23,8 @@ jobs:
           # Prevent use of implicit GitHub Actions read-only GITHUB_TOKEN
           # because javadoc_to_gh_pages pushes commits to the gh-pages branch.
           token: ${{ secrets.GH_TOKEN }}
-          # allow build-bin/javadoc_to_gh_pages to get the full history
+          # Allow build-bin/javadoc_to_gh_pages to fetch and push gh-pages
+          # See https://github.com/actions/checkout/issues/578
           fetch-depth: 0
       - name: Setup java
         uses: actions/setup-java@v4

.github/workflows/docker_push.yml

@@ -14,8 +14,6 @@ jobs:
     steps:
       - name: Checkout Repository
         uses: actions/checkout@v4
-        with:
-          fetch-depth: 1  # only needed to get the sha label
       # Don't attempt to cache Docker. Sensitive information can be stolen
       # via forks, and login session ends up in ~/.docker. This is ok because
       # we publish DOCKER_PARENT_IMAGE to ghcr.io, hence local to the runner.

.github/workflows/test.yml

@@ -36,8 +36,6 @@ jobs:
     steps:
       - name: Checkout Repository
         uses: actions/checkout@v4
-        with:
-          fetch-depth: 0  # full git history for license check
       - name: Setup java
         uses: actions/setup-java@v4
         with:
@@ -78,8 +76,6 @@ jobs:
     steps:
       - name: Checkout Repository
         uses: actions/checkout@v4
-        with:
-          fetch-depth: 1  # -Dlicense.skip=true, so we don't need a full clone
       - name: Setup java
         uses: actions/setup-java@v4
         with:

.github/workflows/test_readme.yml

@@ -38,8 +38,6 @@ jobs:
     steps:
       - name: Checkout Repository
         uses: actions/checkout@v4
-        with:
-          fetch-depth: 1
       - name: Setup java
         uses: actions/setup-java@v4
         with:
@@ -69,8 +67,6 @@ jobs:
     steps:
       - name: Checkout Repository
         uses: actions/checkout@v4
-        with:
-          fetch-depth: 1
       # Remove apt repos that are known to break from time to time.
       # See https://github.com/actions/virtual-environments/issues/323
       - name: Remove broken apt repos

.settings.xml

@@ -1,17 +1,8 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!--
 
-    Copyright 2015-2020 The OpenZipkin Authors
-
-    Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
-    in compliance with the License. You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-    Unless required by applicable law or agreed to in writing, software distributed under the License
-    is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
-    or implied. See the License for the specific language governing permissions and limitations under
-    the License.
+    Copyright The OpenZipkin Authors
+    SPDX-License-Identifier: Apache-2.0
 
 -->
 <settings xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

RELEASE.md

@@ -46,23 +46,6 @@ Here's an example of a snapshot deploy with specified credentials.
 $ export GPG_TTY=$(tty) && GPG_PASSPHRASE=whackamole SONATYPE_USER=adrianmole SONATYPE_PASSWORD=ed6f20bde9123bbb2312b221 build-bin/build-bin/maven/maven_deploy
 ```
 
-## First release of the year
-
-The license plugin verifies license headers of files include a copyright notice indicating the years a file was affected.
-This information is taken from git history. There's a once-a-year problem with files that include version numbers (pom.xml).
-When a release tag is made, it increments version numbers, then commits them to git. On the first release of the year,
-further commands will fail due to the version increments invalidating the copyright statement. The way to sort this out is
-the following:
-
-Before you do the first release of the year, move the SNAPSHOT version back and forth from whatever the current is.
-In-between, re-apply the licenses.
-```bash
-$ ./mvnw versions:set -DnewVersion=1.3.3-SNAPSHOT -DgenerateBackupPoms=false
-$ ./mvnw com.mycila:license-maven-plugin:format
-$ ./mvnw versions:set -DnewVersion=1.3.2-SNAPSHOT -DgenerateBackupPoms=false
-$ git commit -am"Adjusts copyright headers for this year"
-```
-
 ## Manually releasing
 
 If for some reason, you lost access to CI or otherwise cannot get automation to work, bear in mind

benchmarks/pom.xml

@@ -1,17 +1,8 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!--
 
-    Copyright 2015-2024 The OpenZipkin Authors
-
-    Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
-    in compliance with the License. You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-    Unless required by applicable law or agreed to in writing, software distributed under the License
-    is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
-    or implied. See the License for the specific language governing permissions and limitations under
-    the License.
+    Copyright The OpenZipkin Authors
+    SPDX-License-Identifier: Apache-2.0
 
 -->
 <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

benchmarks/src/main/java/zipkin2/EndpointBenchmarks.java

@@ -1,15 +1,6 @@
 /*
- * Copyright 2015-2019 The OpenZipkin Authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
- * in compliance with the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software distributed under the License
- * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
- * or implied. See the License for the specific language governing permissions and limitations under
- * the License.
+ * Copyright The OpenZipkin Authors
+ * SPDX-License-Identifier: Apache-2.0
  */
 package zipkin2;
 

benchmarks/src/main/java/zipkin2/SpanBenchmarks.java

@@ -1,15 +1,6 @@
 /*
- * Copyright 2015-2019 The OpenZipkin Authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
- * in compliance with the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software distributed under the License
- * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
- * or implied. See the License for the specific language governing permissions and limitations under
- * the License.
+ * Copyright The OpenZipkin Authors
+ * SPDX-License-Identifier: Apache-2.0
  */
 package zipkin2;
 

benchmarks/src/main/java/zipkin2/codec/CodecBenchmarks.java

@@ -1,15 +1,6 @@
 /*
- * Copyright 2015-2024 The OpenZipkin Authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
- * in compliance with the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software distributed under the License
- * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
- * or implied. See the License for the specific language governing permissions and limitations under
- * the License.
+ * Copyright The OpenZipkin Authors
+ * SPDX-License-Identifier: Apache-2.0
  */
 package zipkin2.codec;
 

benchmarks/src/main/java/zipkin2/codec/JacksonSpanDecoder.java

@@ -1,15 +1,6 @@
 /*
- * Copyright 2015-2019 The OpenZipkin Authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
- * in compliance with the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software distributed under the License
- * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
- * or implied. See the License for the specific language governing permissions and limitations under
- * the License.
+ * Copyright The OpenZipkin Authors
+ * SPDX-License-Identifier: Apache-2.0
  */
 package zipkin2.codec;
 

benchmarks/src/main/java/zipkin2/codec/JsonCodecBenchmarks.java

@@ -1,15 +1,6 @@
 /*
- * Copyright 2015-2020 The OpenZipkin Authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
- * in compliance with the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software distributed under the License
- * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
- * or implied. See the License for the specific language governing permissions and limitations under
- * the License.
+ * Copyright The OpenZipkin Authors
+ * SPDX-License-Identifier: Apache-2.0
  */
 package zipkin2.codec;
 

benchmarks/src/main/java/zipkin2/codec/MoshiSpanDecoder.java

@@ -1,15 +1,6 @@
 /*
- * Copyright 2015-2024 The OpenZipkin Authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
- * in compliance with the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software distributed under the License
- * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
- * or implied. See the License for the specific language governing permissions and limitations under
- * the License.
+ * Copyright The OpenZipkin Authors
+ * SPDX-License-Identifier: Apache-2.0
  */
 package zipkin2.codec;
 

benchmarks/src/main/java/zipkin2/codec/ProtoCodecBenchmarks.java

@@ -1,15 +1,6 @@
 /*
- * Copyright 2015-2020 The OpenZipkin Authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
- * in compliance with the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software distributed under the License
- * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
- * or implied. See the License for the specific language governing permissions and limitations under
- * the License.
+ * Copyright The OpenZipkin Authors
+ * SPDX-License-Identifier: Apache-2.0
  */
 package zipkin2.codec;
 

benchmarks/src/main/java/zipkin2/codec/ProtobufSpanDecoder.java

@@ -1,15 +1,6 @@
 /*
- * Copyright 2015-2024 The OpenZipkin Authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
- * in compliance with the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software distributed under the License
- * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
- * or implied. See the License for the specific language governing permissions and limitations under
- * the License.
+ * Copyright The OpenZipkin Authors
+ * SPDX-License-Identifier: Apache-2.0
  */
 package zipkin2.codec;
 

benchmarks/src/main/java/zipkin2/codec/WireSpanDecoder.java

@@ -1,15 +1,6 @@
 /*
- * Copyright 2015-2024 The OpenZipkin Authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
- * in compliance with the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software distributed under the License
- * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
- * or implied. See the License for the specific language governing permissions and limitations under
- * the License.
+ * Copyright The OpenZipkin Authors
+ * SPDX-License-Identifier: Apache-2.0
  */
 package zipkin2.codec;
 

benchmarks/src/main/java/zipkin2/collector/MetricsBenchmarks.java

@@ -1,15 +1,6 @@
 /*
- * Copyright 2015-2023 The OpenZipkin Authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
- * in compliance with the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software distributed under the License
- * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
- * or implied. See the License for the specific language governing permissions and limitations under
- * the License.
+ * Copyright The OpenZipkin Authors
+ * SPDX-License-Identifier: Apache-2.0
  */
 package zipkin2.collector;
 

benchmarks/src/main/java/zipkin2/elasticsearch/internal/BulkRequestBenchmarks.java

@@ -1,15 +1,6 @@
 /*
- * Copyright 2015-2023 The OpenZipkin Authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
- * in compliance with the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software distributed under the License
- * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
- * or implied. See the License for the specific language governing permissions and limitations under
- * the License.
+ * Copyright The OpenZipkin Authors
+ * SPDX-License-Identifier: Apache-2.0
  */
 package zipkin2.elasticsearch.internal;
 

benchmarks/src/main/java/zipkin2/internal/DelayLimiterBenchmarks.java

@@ -1,15 +1,6 @@
 /*
- * Copyright 2015-2020 The OpenZipkin Authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
- * in compliance with the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software distributed under the License
- * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
- * or implied. See the License for the specific language governing permissions and limitations under
- * the License.
+ * Copyright The OpenZipkin Authors
+ * SPDX-License-Identifier: Apache-2.0
  */
 package zipkin2.internal;
 

benchmarks/src/main/java/zipkin2/internal/ReadBufferBenchmarks.java

@@ -1,15 +1,6 @@
 /*
- * Copyright 2015-2019 The OpenZipkin Authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
- * in compliance with the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software distributed under the License
- * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
- * or implied. See the License for the specific language governing permissions and limitations under
- * the License.
+ * Copyright The OpenZipkin Authors
+ * SPDX-License-Identifier: Apache-2.0
  */
 package zipkin2.internal;
 

benchmarks/src/main/java/zipkin2/internal/WriteBufferBenchmarks.java

@@ -1,15 +1,6 @@
 /*
- * Copyright 2015-2024 The OpenZipkin Authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
- * in compliance with the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software distributed under the License
- * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
- * or implied. See the License for the specific language governing permissions and limitations under
- * the License.
+ * Copyright The OpenZipkin Authors
+ * SPDX-License-Identifier: Apache-2.0
  */
 package zipkin2.internal;