From 627159b9f2d6165b7d51f811180c03770a6377bb Mon Sep 17 00:00:00 2001
From: MerryMage <MerryMage@users.noreply.github.com>
Date: Wed, 15 Aug 2018 13:28:13 +0100
Subject: [PATCH] externals: Document subtrees

---
 externals/README.md | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)
 create mode 100644 externals/README.md

diff --git a/externals/README.md b/externals/README.md
new file mode 100644
index 00000000..7a141c83
--- /dev/null
+++ b/externals/README.md
@@ -0,0 +1,19 @@
+This repository uses subtrees to manage some of its externals.
+
+## Initial setup
+
+```
+git remote add externals-fmt https://github.com/fmtlib/fmt.git
+git remote add externals-xbyak https://github.com/herumi/xbyak.git
+```
+
+## Updating
+
+Change `<ref>` to refer to the appropriate git reference.
+
+```
+git fetch externals-fmt
+git fetch externals-xbyak
+git subtree pull --squash --prefix=externals/fmt externals-fmt <ref>
+git subtree pull --squash --prefix=externals/xbyak externals-xbyak <ref>
+```