Add GIT_VERSION env var support (#928)

Add GIT_VERSION env var support

Author: FinlayRJW

changelog/@unreleased/pr-928.v2.yml

@@ -0,0 +1,5 @@
+type: improvement
+improvement:
+  description: Add `GIT_VERSION` env var support
+  links:
+  - https://github.com/palantir/gradle-git-version/pull/928

src/main/java/com/palantir/gradle/gitversion/VersionDetailsImpl.java

@@ -43,6 +43,11 @@ final class VersionDetailsImpl implements VersionDetails {
 
     @Override
     public String getVersion() {
+        String envVersion = System.getenv("GIT_VERSION");
+        if (envVersion != null && !envVersion.isEmpty()) {
+            return envVersion;
+        }
+
         if (description() == null) {
             return "unspecified";
         }

src/test/groovy/com/palantir/gradle/gitversion/GitVersionPluginTests.groovy

@@ -193,6 +193,34 @@ class GitVersionPluginTests extends Specification {
         buildResult.output.contains(":printVersion\n1.0.0\n")
     }
 
+    def 'gitVersion() uses GIT_VERSION environment variable if it is set' () {
+        given:
+        buildFile << '''
+            plugins {
+                id 'com.palantir.git-version'
+            }
+            version gitVersion()
+        '''.stripIndent()
+        gitIgnoreFile << 'build'
+        Git git = new Git(projectDir, true)
+        git.runGitCommand("init", projectDir.toString())
+        git.runGitCommand("add", ".")
+        git.runGitCommand("commit", "-m", "'initial commit'")
+        git.runGitCommand("tag", "-a", "1.0.0", "-m", "1.0.0")
+
+        when:
+        BuildResult normalResult = with('printVersion').build()
+
+        then:
+        normalResult.output.contains(":printVersion\n1.0.0\n")
+
+        when:
+        BuildResult overriddenResult = with(Optional.empty(), Optional.of(Map.of("GIT_VERSION", "999")),'printVersion').build()
+
+        then:
+        overriddenResult.output.contains(":printVersion\n999\n")
+    }
+
     def 'git describe when lightweight tag is present' () {
         given:
         buildFile << '''
@@ -701,10 +729,10 @@ class GitVersionPluginTests extends Specification {
     }
 
     private GradleRunner with(String... tasks) {
-        return with(Optional.empty(), tasks)
+        return with(Optional.empty(), Optional.empty(), tasks)
     }
 
-    private GradleRunner with(Optional<String> gradleVersion, String... tasks) {
+    private GradleRunner with(Optional<String> gradleVersion, Optional<Map<String, String>> envVars, String... tasks) {
         List<String> arguments = new ArrayList<>(['--stacktrace'])
         arguments.addAll(tasks)
 
@@ -714,6 +742,11 @@ class GitVersionPluginTests extends Specification {
                 .withArguments(arguments)
 
         gradleVersion.ifPresent({ version -> gradleRunner.withGradleVersion(version) })
+        envVars.ifPresent {env ->
+            Map<String, String> systemEnv = new HashMap<>(System.getenv())
+            systemEnv.putAll(env)
+            gradleRunner.withEnvironment(systemEnv)
+        }
 
         return gradleRunner
     }