From 3d996a84cc754cea106ac490099f3cd24f546be8 Mon Sep 17 00:00:00 2001
From: dearblue <dearblue@users.osdn.me>
Date: Sun, 12 Feb 2023 21:02:31 +0900
Subject: [PATCH] Takes the environment variable `DESTDIR` in `rake install`

If the environment variable `DESTDIR` is set, the writing destination is `<DESTDIR>/<PREFIX>/...`.
It is assumed to be used for package work.
---
 doc/guides/compile.md | 4 ++++
 lib/mruby/build.rb    | 1 +
 tasks/install.rake    | 2 +-
 3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/doc/guides/compile.md b/doc/guides/compile.md
index 03450cd6a..08dedbf9d 100644
--- a/doc/guides/compile.md
+++ b/doc/guides/compile.md
@@ -595,6 +595,9 @@ The `PREFIX` environment variable affects all build targets and changes the `/us
 The `MRuby::Build#install_prefix` can be set for each individual build target.
 In this case, the environment variable `PREFIX` is ignored.
 
+Also, if the environment variable `DESTDIR` is set, it will prepend to the path obtained by `install_prefix` to determine the final write directory.
+This is intended for temporary file expansion by the user's package work.
+
 ---
 
 To summarize:
@@ -602,6 +605,7 @@ To summarize:
 - The default value of the environment variable `PREFIX` is `/usr/local`.
 - For the "host" build target, the default value of `MRuby::Build#install_prefix` is `<PREFIX>`.
 - For a build target other than "host", the default value of `MRuby::Build#install_prefix` is `<PREFIX>/mruby/<build-name>`.
+- If the environment variable `DESTDIR` is set, the actual write directory is `<DESTDIR>/<MRuby::Build#install_prefix>`.
 
 ## Tips
 
diff --git a/lib/mruby/build.rb b/lib/mruby/build.rb
index cfae8c8a1..71aed7667 100644
--- a/lib/mruby/build.rb
+++ b/lib/mruby/build.rb
@@ -9,6 +9,7 @@ module MRuby
   autoload :Presym, "mruby/presym"
 
   INSTALL_PREFIX = ENV['PREFIX'] || ENV['INSTALL_PREFIX'] || '/usr/local'
+  INSTALL_DESTDIR = ENV['DESTDIR'] || ''
 
   class << self
     def targets
diff --git a/tasks/install.rake b/tasks/install.rake
index ccb0c1a3c..234bec8d8 100644
--- a/tasks/install.rake
+++ b/tasks/install.rake
@@ -13,7 +13,7 @@ task "install:bin"
 MRuby.each_target do |build|
   next if build.internal?
 
-  prefix = build.install_prefix
+  prefix = File.join(MRuby::INSTALL_DESTDIR, build.install_prefix)
 
   task "install:full" => "install:full:#{build.name}"