Switch to a submodule for harfbuzz. (#205)

This simplifies updating as well as reducing the amount of churn
in this repo when updating.

Author: waywardmonkeys

.github/workflows/main.yml

@@ -15,6 +15,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
+        with:
+          submodules: true
 
       - name: install harfbuzz from apt
         run: |
@@ -37,6 +39,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
+        with:
+          submodules: true
 
       - name: Install stable toolchain
         uses: dtolnay/rust-toolchain@stable
@@ -64,6 +68,8 @@ jobs:
 
     steps:
       - uses: actions/checkout@v3
+        with:
+          submodules: true
 
       - name: install harfbuzz from homebrew
         run: |
@@ -91,6 +97,8 @@ jobs:
 
     steps:
       - uses: actions/checkout@v3
+        with:
+          submodules: true
 
       - name: Install stable toolchain
         uses: dtolnay/rust-toolchain@stable
@@ -114,6 +122,8 @@ jobs:
 
     steps:
       - uses: actions/checkout@v3
+        with:
+          submodules: true
 
       - name: Install stable toolchain
         uses: dtolnay/rust-toolchain@stable
@@ -132,6 +142,8 @@ jobs:
 
     steps:
       - uses: actions/checkout@v3
+        with:
+          submodules: true
 
       - uses: mymindstorm/setup-emsdk@v12
         with:
@@ -151,6 +163,8 @@ jobs:
 
     steps:
       - uses: actions/checkout@v3
+        with:
+          submodules: true
 
       - name: Install stable toolchain
         uses: dtolnay/rust-toolchain@stable

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "harfbuzz-sys/harfbuzz"]
+	path = harfbuzz-sys/harfbuzz
+	url = https://github.com/harfbuzz/harfbuzz

README.md

@@ -1,7 +1,23 @@
-## rust-harfbuzz
+# rust-harfbuzz
 
 [![Build Status](https://github.com/servo/rust-harfbuzz/actions/workflows/main.yml/badge.svg)](https://github.com/servo/rust-harfbuzz/actions)
 
 [Documentation](https://docs.rs/harfbuzz-sys)
 
 Bindings to the HarfBuzz text shaping engine.
+
+## Vendored Harfbuzz Sources
+
+This repository contains a vendored copy of the `harfbuzz` sources
+as a git submodule. If building with the `bundled` feature, be sure
+to initialize submodules:
+
+```
+git clone --recursive https://github.com/servo/rust-harfbuzz.git
+```
+
+Or, after a clone:
+
+```
+git submodule update --init
+```