From 773481d84e11482fe3b7c0bcc5b5b63ef41976dc Mon Sep 17 00:00:00 2001
From: Eugene Yokota <eed3si9n@gmail.com>
Date: Wed, 16 Oct 2024 02:36:28 -0400
Subject: [PATCH] Command chaining

---
 .../scala/com/geirsson/CiReleasePlugin.scala  | 28 ++++++++-----
 .../scala/com/geirsson/CiReleaseTest.scala    |  8 ++++
 readme.md                                     | 39 +++++++++++++++++++
 3 files changed, 66 insertions(+), 9 deletions(-)

diff --git a/plugin/src/main/scala/com/geirsson/CiReleasePlugin.scala b/plugin/src/main/scala/com/geirsson/CiReleasePlugin.scala
index 8286ffa..3c46d4f 100644
--- a/plugin/src/main/scala/com/geirsson/CiReleasePlugin.scala
+++ b/plugin/src/main/scala/com/geirsson/CiReleasePlugin.scala
@@ -244,15 +244,25 @@ object CiReleasePlugin extends AutoPlugin {
 
   def backPubVersionToCommand(ver: String): String =
     if (ver.contains("@")) {
-      val afterAt = ver.split("@").drop(1).mkString("@")
-      val cmd =
-        if (afterAt.contains("#")) afterAt.split("#").head
-        else afterAt
-      if (cmd.isEmpty) sys.error(s"Invalid back-publish version: $ver")
-      else {
-        if (!cmd.head.isDigit) cmd
-        else if (cmd.contains(".x")) s";++${cmd};publishSigned"
-        else s";++${cmd}!;publishSigned"
+      val nonComment =
+        if (ver.contains("#")) ver.split("#").head
+        else ver
+      val commands0 = nonComment.split("@").toList.drop(1)
+      var nonDigit = false
+      val commands = (commands0.map { cmd =>
+        if (cmd.isEmpty) sys.error(s"Invalid back-publish version: $ver")
+        else {
+          if (!cmd.head.isDigit) {
+            nonDigit = true
+            cmd
+          }
+          else if (cmd.contains(".x")) s"++${cmd}"
+          else s"++${cmd}!"
+        }
+      }) ::: (if (nonDigit) Nil else List("publishSigned"))
+      commands match {
+        case x :: Nil => x
+        case xs       => xs.mkString(";", ";", "")
       }
     } else "+publishSigned"
 
diff --git a/plugin/src/test/scala/com/geirsson/CiReleaseTest.scala b/plugin/src/test/scala/com/geirsson/CiReleaseTest.scala
index 4cdd39f..9de7c71 100644
--- a/plugin/src/test/scala/com/geirsson/CiReleaseTest.scala
+++ b/plugin/src/test/scala/com/geirsson/CiReleaseTest.scala
@@ -26,6 +26,14 @@ class CiReleaseTest extends munit.FunSuite {
     assertEquals(dropBackPubCommand("1.1.0@+foo/publishSigned"), expectedVer)
   }
 
+  test("Commands can be chained") {
+    assertEquals(backPubVersionToCommand("1.1.0@2.12.20@foo/publishSigned"), ";++2.12.20!;foo/publishSigned")
+    assertEquals(dropBackPubCommand("1.1.0@2.12.20@foo/publishSigned"), expectedVer)
+
+    assertEquals(backPubVersionToCommand("1.1.0@foo/something@bar/publishSigned"), ";foo/something;bar/publishSigned")
+    assertEquals(dropBackPubCommand("1.1.0@foo/something@bar/publishSigned"), expectedVer)
+  }
+
   test("Treat # as comments") {
     assertEquals(backPubVersionToCommand("1.1.0#comment"), "+publishSigned")
     assertEquals(dropBackPubCommand("1.1.0#comment"), expectedVer)
diff --git a/readme.md b/readme.md
index 7f2ed1c..615afa6 100644
--- a/readme.md
+++ b/readme.md
@@ -356,6 +356,45 @@ page will look like this:
 
 Enjoy 👌
 
+### Back-publishing support
+
+sbt-ci-release implements a mini-DSL for the Git tag for back publishing purpose, which is useful if you maintain a compiler plugin, library for Scala Native, or an sbt plugin during 2.x migration etc.
+
+```
+v1.2.3[@3.x|@2.n.x|@a.b.c][@command][#comment]
+```
+
+- `#` is used for comments, which is useful if you need to use the same command multiple times
+- `@3.x` expands to `++3.x`, and if no other commands follow, `;++3.x;publishSigned`
+- `@2.13.x` expands to `++2.13.x`, and if no other commands follow, `;++2.13.x;publishSigned`
+- Other commands such as `@foo/publishSigned` expands to `foo/publishSigned`
+
+#### Case 1: Publish all subprojects for Scala 2.13.15
+
+`v1.2.3@2.13.15`
+
+#### Case 2: Publish all subprojects for Scala 3.x
+
+`v1.2.3@3.x`. Optionally we can add a comment: `v1.2.3@3.x#comment`.
+
+We can use this to back publish sbt 2.x plugins.
+
+1. Branch off of `v1.2.3` to create `release/1.2.3` branch, and send a PR to bump sbt version
+2. Tag the brach to `v1.2.3@3.x#sbt2.0.0-Mn`
+
+#### Case 3: Publish some subprojects for Scala 2.13.15
+
+`v1.2.3@2.13.15@foo/publishSigned`
+
+You can create a subproject to aggregate 2 or more subprojects.
+
+#### Case 4: Publish some subprojects for supported Scala versions
+
+`v1.2.3@+foo_native/publishSigned#comment`
+
+1. Branch off of `v1.2.3` to create `release/1.2.3` branch, and send a PR to bump the Scala Native version.
+2. Tag the branch to `v1.2.3@+foo_native/publishSigned#native=0.5`
+
 ## FAQ
 
 ### How do I publish to Sonatype Central?