From b20b07dc3de529e084655e85aacd272ce416acc5 Mon Sep 17 00:00:00 2001
From: Ross Light <ross@zombiezen.com>
Date: Fri, 28 Jul 2023 15:59:48 -0700
Subject: [PATCH] .github: use Nix to build Git

---
 .github/workflows/build.yml | 67 ++++++++++---------------------------
 flake.nix                   | 16 ++++-----
 2 files changed, 26 insertions(+), 57 deletions(-)

diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 4983224..887dd5f 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -23,90 +23,59 @@ on:
 jobs:
   linux:
     name: Linux
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     strategy:
       matrix:
         git:
-        - "2.27.0"  # latest
-        - "2.25.1"  # Ubuntu LTS 20.04 focal
-        - "2.20.1"  # Debian buster
-        - "2.17.1"  # Ubuntu LTS 18.04 bionic
+          - "2.27.0"  # latest
+          - "2.25.1"  # Ubuntu LTS 20.04 focal
+          - "2.20.1"  # Debian buster
+          - "2.17.1"  # Ubuntu LTS 18.04 bionic
     steps:
-    - name: Install Git dependencies
-      run: |
-        sudo apt-get update &&
-        sudo apt-get install -y --no-install-recommends \
-          gettext \
-          libcurl4-gnutls-dev \
-          libexpat1-dev \
-          libssl-dev \
-          libz-dev \
-          xz-utils
-    - name: Set up Go
-      uses: actions/setup-go@v4
-      with:
-        go-version: "1.19"
     - name: Check out code
       uses: actions/checkout@v3
-    - name: Install Git
-      run: misc/build-git.bash ~/git ${{ matrix.git }}
-    - name: Download dependencies
-      run: go mod download
-      env:
-        GO111MODULE: on
+    - name: Install Nix
+      uses: cachix/install-nix-action@v22
     - name: Run tests
       run: |
-        PATH="$HOME/git/bin-wrappers:$PATH" \
+        git_attr="$(echo "$GIT_VERSION" | sed -e 's/\./_/g')"
+        nix shell ".#$git_attr" '.#go' --command \
           go test \
             -mod=readonly \
             -v \
             -race \
             ./...
       env:
+        GIT_VERSION: ${{ matrix.git }}
         GO111MODULE: on
   mac:
     name: macOS
     runs-on: macOS-latest
     steps:
-    - name: Install xz
-      run: brew update && brew install xz
-    - name: Set up Go
-      uses: actions/setup-go@v4
-      with:
-        go-version: "1.19"
     - name: Check out code
       uses: actions/checkout@v3
-    - name: Install Git
-      run: misc/build-git.bash ~/git 2.27.0
-    - name: Download dependencies
-      run: go mod download
-      env:
-        GO111MODULE: on
+    - name: Install Nix
+      uses: cachix/install-nix-action@v22
     - name: Run tests
       run: |
-        PATH="$HOME/git/bin-wrappers:$PATH" \
+        git_attr="$(echo "$GIT_VERSION" | sed -e 's/\./_/g')"
+        nix shell ".#$git_attr" '.#go' --command \
           go test \
             -mod=readonly \
             -v \
             -race \
             ./...
       env:
-        GO111MODULE: on
+        GIT_VERSION: "2.27.0"
   windows:
     name: Windows
     runs-on: windows-latest
     steps:
+    - name: Check out code
+      uses: actions/checkout@v3
     - name: Set up Go
       uses: actions/setup-go@v4
       with:
-        go-version: "1.19"
-    - name: Check out code
-      uses: actions/checkout@v3
-    - name: Download dependencies
-      run: go mod download
-      env:
-        GO111MODULE: on
+        go-version: "1.20"
     - name: Run tests
       run: go test -mod=readonly -v -race ./...
-      env:
-        GO111MODULE: on
diff --git a/flake.nix b/flake.nix
index 75ef5ef..b75097c 100644
--- a/flake.nix
+++ b/flake.nix
@@ -38,6 +38,8 @@
       let
         pkgs = import nixpkgs { inherit system; };
       in {
+        packages.go = pkgs.go_1_20;
+
         packages.git = pkgs.git;
 
         packages.git_2_17_1 = self.lib.buildGit {
@@ -79,16 +81,14 @@
             outputs = [ "out" ];
           });
 
-        devShells.default = self.lib.mkShell { inherit pkgs; };
+        devShells.default = pkgs.mkShell {
+          packages = [
+            self.packages.${system}.go
+            pkgs.git
+          ];
+        };
       }
     ) // {
-      lib.mkShell = { pkgs, git ? pkgs.git }: pkgs.mkShell {
-        packages = [
-          pkgs.go_1_20
-          git
-        ];
-      };
-
       lib.buildGit = { pkgs, packagePath, args ? {} }:
         let
           defaultArgs = {