Use full Git hash in generated version files (#12001)

fix: Use full Git hash in generated version files

Git chooses the minimum unique abbreviation when `--short` is used.
That abbreviation can have a different length when runners have
different Git objects, even when both jobs build the same commit. This
produces different version files and prevents reproducible JARs across
jobs.

Emit the full commit hash in the version file instead, for example:

1.65.0-SNAPSHOT~846103dfeb02cb7e162b0404af6d87a4882e2e91

Also, capture the project name during configuration so the task action
does not access the Gradle project.

https://git-scm.com/docs/git-rev-parse#Documentation/git-rev-parse.txt---shortltlengthgt

---

The validate build scan reported for `:dd-trace-api:writeVersionNumberFile`:

```
The task was not up-to-date because of the following reasons:
Value of input property 'gitHash' has changed for task ':dd-trace-api:writeVersionNumberFile'
```

chore: Keep a 10 char hex abbreviation

The tracer version string is propagated today by a few components:
* tracer
* telemetry
* remote config poller
* crash-tracking

In all cases the tracer version is processed as an "opaque" string and
ends up as a tag value for the tracer.

The hash in the version string packaged in the agent jar shows the
abbreviation has been growing over the years 7, 8, 9, 10, (and probaly
soon 11) chars over the repo's history.

Given the hash surfaces in UI, let's truncate it to 10 chars.

https://git-scm.com/docs/hash-function-transition.html

Co-authored-by: brice.dutheil <brice.dutheil@datadoghq.com>

Author: bric3

buildSrc/src/main/kotlin/datadog/gradle/plugin/version/WriteVersionFile.kt

@@ -1,12 +1,15 @@
 package datadog.gradle.plugin.version
 
+import org.checkerframework.checker.units.qual.g
 import org.gradle.api.DefaultTask
 import org.gradle.api.file.DirectoryProperty
 import org.gradle.api.file.ProjectLayout
 import org.gradle.api.model.ObjectFactory
 import org.gradle.api.provider.Property
 import org.gradle.api.provider.ProviderFactory
 import org.gradle.api.tasks.Input
+import org.gradle.api.tasks.Internal
+import org.gradle.api.tasks.Optional
 import org.gradle.api.tasks.OutputDirectory
 import org.gradle.api.tasks.TaskAction
 import org.gradle.kotlin.dsl.property
@@ -27,20 +30,28 @@ abstract class WriteVersionFile @Inject constructor(
     .convention(
       providerFactory.of(GitCommandValueSource::class.java) {
         parameters {
-          gitCommand.addAll("git", "rev-parse", "--short", "HEAD")
+          gitCommand.addAll("git", "rev-parse", "HEAD")
           workingDirectory.set(layout.projectDirectory)
         }
       }
     )
 
+  @get:Input
+  val gitHashTruncation: Property<Int> = objects.property<Int>()
+    .convention(10)
+
+  @get:Input
+  val projectName: Property<String> = objects.property<String>()
+    .convention(project.name)
+
   @get:OutputDirectory
   val outputDirectory: DirectoryProperty = objects.directoryProperty()
     .convention(layout.buildDirectory.dir("generated/version"))
 
   @TaskAction
   fun writeVersionFile() {
-    val versionFile = outputDirectory.file("${project.name}.version").get().asFile
+    val versionFile = outputDirectory.file("${projectName.get()}.version").get().asFile
     versionFile.parentFile.mkdirs()
-    versionFile.writeText("${version.get()}~${gitHash.get()}")
+    versionFile.writeText("${version.get()}~${gitHash.get().take(gitHashTruncation.get())}")
   }
 }

buildSrc/src/test/kotlin/datadog/gradle/plugin/version/WriteVersionFilePluginTest.kt

@@ -9,8 +9,9 @@ class WriteVersionFilePluginTest : VersionPluginsFixture() {
 
   @Test
   fun `writes version file in version~hash format`() {
+    // task truncation convention is 10
     assertVersionFile(
-      expectedContentRegex = "1\\.2\\.3~[0-9a-f]+",
+      expectedContentRegex = "1\\.2\\.3~[0-9a-f]{10}",
       beforeGradle = {
         initGitRepo()
       },