From b98b5dffa61ffa019a45f6032d857a47cfd9f10c Mon Sep 17 00:00:00 2001
From: Eugene Yokota <eed3si9n@gmail.com>
Date: Fri, 22 Mar 2019 02:28:14 -0400
Subject: [PATCH] use tag when available

---
 build.sbt | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/build.sbt b/build.sbt
index 847e67f07..1f13669c9 100644
--- a/build.sbt
+++ b/build.sbt
@@ -61,12 +61,15 @@ def commonSettings: Seq[Setting[_]] = Def.settings(
   testOptions in Test += Tests.Argument(TestFrameworks.ScalaCheck, "-w", "1"),
   testOptions in Test += Tests.Argument(TestFrameworks.ScalaCheck, "-verbosity", "2"),
   javacOptions in compile ++= Seq("-Xlint", "-Xlint:-serial"),
-  scalacOptions in (Compile, doc) ++= {
+  Compile / doc / scalacOptions ++= {
+    import scala.sys.process._
+    val devnull = ProcessLogger(_ => ())
+    val tagOrSha = ("git describe --exact-match" #|| "git rev-parse HEAD").lineStream(devnull).head
     Seq(
       "-sourcepath",
       (baseDirectory in LocalRootProject).value.getAbsolutePath,
       "-doc-source-url",
-      s"""https://github.com/sbt/sbt/tree/${sys.process.Process("git rev-parse HEAD").lineStream_!.head}€{FILE_PATH}.scala"""
+      s"https://github.com/sbt/sbt/tree/$tagOrSha€{FILE_PATH}.scala"
     )
   },
   crossScalaVersions := Seq(baseScalaVersion),