Populate RepositoryBranch automatically

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Fixes #57

src/NuGetizer.Tasks/NuGetizer.PackageMetadata.targets

@@ -21,6 +21,34 @@ Copyright (c) .NET Foundation. All rights reserved.
 
     <NuGetizerPackageMetadataImported>true</NuGetizerPackageMetadataImported>
   </PropertyGroup>
+
+  <PropertyGroup Condition="'$(RepositoryBranch)' == ''">
+    <!-- GitHub Actions: https://docs.github.com/en/actions/reference/environment-variables#default-environment-variables -->
+    <RepositoryBranch Condition="'$(RepositoryBranch)' == '' and '$(GITHUB_REF)' != '' and $(GITHUB_REF.Contains('refs/pull/'))">pr$(GITHUB_REF.Replace('refs/pull/', '').Replace('/merge', ''))</RepositoryBranch>
+    <RepositoryBranch Condition="'$(RepositoryBranch)' == '' and '$(GITHUB_REF)' != ''">$(GITHUB_REF.Replace('refs/heads/', '').Replace('refs/tags/', ''))</RepositoryBranch>
+    <!-- Azure DevOps: https://docs.microsoft.com/en-us/azure/devops/pipelines/build/variables -->
+    <RepositoryBranch Condition="'$(RepositoryBranch)' == '' and '$(BUILD_SOURCEBRANCH)' != ''">$(BUILD_SOURCEBRANCH.Replace('refs/heads/', '').Replace('refs/tags/', ''))</RepositoryBranch>
+    <!-- AppVeyor: https://www.appveyor.com/docs/environment-variables/ -->
+    <RepositoryBranch Condition="'$(RepositoryBranch)' == '' and '$(APPVEYOR_PULL_REQUEST_NUMBER)' != ''">pr$(APPVEYOR_PULL_REQUEST_NUMBER)</RepositoryBranch>
+    <RepositoryBranch Condition="'$(RepositoryBranch)' == '' and '$(APPVEYOR_REPO_TAG_NAME)' != ''">$(APPVEYOR_REPO_TAG_NAME)</RepositoryBranch>
+    <RepositoryBranch Condition="'$(RepositoryBranch)' == '' and '$(APPVEYOR_REPO_BRANCH)' != ''">$(APPVEYOR_REPO_BRANCH)</RepositoryBranch>
+    <!--TravisCI: https://docs.travis-ci.com/user/environment-variables/ -->
+    <RepositoryBranch Condition="'$(RepositoryBranch)' == '' and '$(TRAVIS_PULL_REQUEST)' != '' and '$(TRAVIS_PULL_REQUEST)' != 'false'">pr$(TRAVIS_PULL_REQUEST)</RepositoryBranch>
+    <RepositoryBranch Condition="'$(RepositoryBranch)' == '' and '$(TRAVIS_BRANCH)' != ''">$(TRAVIS_BRANCH)</RepositoryBranch>
+    <!-- CircleCI: https://circleci.com/docs/2.0/env-vars/ -->
+    <RepositoryBranch Condition="'$(RepositoryBranch)' == '' and '$(CIRCLE_PR_NUMBER)' != ''">pr$(CIRCLE_PR_NUMBER)</RepositoryBranch>
+    <RepositoryBranch Condition="'$(RepositoryBranch)' == '' and '$(CIRCLE_TAG)' != ''">$(CIRCLE_TAG)</RepositoryBranch>
+    <RepositoryBranch Condition="'$(RepositoryBranch)' == '' and '$(CIRCLE_BRANCH)' != ''">$(CIRCLE_BRANCH)</RepositoryBranch>
+    <!-- GitLab: https://docs.gitlab.com/ee/ci/variables/predefined_variables.html -->
+    <RepositoryBranch Condition="'$(RepositoryBranch)' == '' and '$(CI_COMMIT_TAG)' != ''">$(CI_COMMIT_TAG)</RepositoryBranch>
+    <RepositoryBranch Condition="'$(RepositoryBranch)' == '' and '$(CI_MERGE_REQUEST_IID)' != ''">pr$(CI_MERGE_REQUEST_IID)</RepositoryBranch>
+    <RepositoryBranch Condition="'$(RepositoryBranch)' == '' and '$(CI_EXTERNAL_PULL_REQUEST_IID)' != ''">pr$(CI_EXTERNAL_PULL_REQUEST_IID)</RepositoryBranch>
+    <RepositoryBranch Condition="'$(RepositoryBranch)' == '' and '$(CI_COMMIT_BRANCH)' != ''">$(CI_COMMIT_BRANCH)</RepositoryBranch>
+    <!-- Buddy: https://buddy.works/docs/pipelines/environment-variables#default-environment-variables -->
+    <RepositoryBranch Condition="'$(RepositoryBranch)' == '' and '$(BUDDY_EXECUTION_PULL_REQUEST_NO)' != ''">pr$(BUDDY_EXECUTION_PULL_REQUEST_NO)</RepositoryBranch>
+    <RepositoryBranch Condition="'$(RepositoryBranch)' == '' and '$(BUDDY_EXECUTION_TAG)' != ''">$(BUDDY_EXECUTION_TAG)</RepositoryBranch>
+    <RepositoryBranch Condition="'$(RepositoryBranch)' == '' and '$(BUDDY_EXECUTION_BRANCH)' != ''">$(BUDDY_EXECUTION_BRANCH)</RepositoryBranch>
+  </PropertyGroup>
 
   <ItemDefinitionGroup>
     <PackageMetadata>

src/NuGetizer.Tests/given_sourcelink.cs

@@ -1,4 +1,5 @@
-using Xunit;
+using System;
+using Xunit;
 using Xunit.Abstractions;
 
 namespace NuGetizer
@@ -12,6 +13,9 @@ public class given_sourcelink
         [Fact]
         public void when_getting_metadata_then_adds_repository_info()
         {
+            if (string.IsNullOrEmpty(Environment.GetEnvironmentVariable("GITHUB_REF")))
+                Environment.SetEnvironmentVariable("GITHUB_REF", "refs/heads/main");
+
             var result = Builder.BuildProject(@"
 <Project Sdk='Microsoft.NET.Sdk'>
   <PropertyGroup>
@@ -33,6 +37,7 @@ public void when_getting_metadata_then_adds_repository_info()
             Assert.Equal("git", metadata.GetMetadata("RepositoryType"));
             Assert.Equal(ThisAssembly.Project.PrivateRepositoryUrl, metadata.GetMetadata("RepositoryUrl"));
             Assert.NotEmpty(metadata.GetMetadata("RepositoryCommit"));
+            Assert.NotEmpty(metadata.GetMetadata("RepositoryBranch"));
         }
 
         [Fact]