Add CI and fix test failures on Linux

.github/workflows/build.yml

@@ -0,0 +1,39 @@
+name: CI
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+  workflow_dispatch:
+
+jobs:
+  build:
+    strategy:
+      fail-fast: false
+      matrix:
+        zig-version: ["0.14.0"]
+        os:
+          - ubuntu-latest
+          # - macos-latest # Does not build yet
+          # - windows-latest # Does not pass tests
+    runs-on: ${{ matrix.os }}
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Zig
+        uses: mlugg/setup-zig@v1
+        with:
+          version: ${{ matrix.zig-version }}
+
+      - name: Check Formatting
+        run: zig fmt --ast-check --check .
+
+      - name: Build
+        run: zig build --summary all
+
+      - name: Test
+        run: zig build test --summary all

build.zig

@@ -389,6 +389,26 @@ pub fn build(b: *std.Build) !void {
 
     const test_step = b.step("test", "Run core unit tests (requires python)");
     {
+        // Fix the test fixture file permissions. This is necessary because Zig does
+        // not respect the execute permission on arbitrary files it extracts from dependencies.
+        // Since we need those files to have the execute permission set for tests to
+        // run successfully, we need to patch them before we bake them into the
+        // test executable. While modifying the global cache is hacky, it wont break
+        // hashes for the same reason above.
+        for ([_]std.Build.LazyPath{
+            libgit_root.path(b, "tests/resources/filemodes/exec_on"),
+            libgit_root.path(b, "tests/resources/filemodes/exec_off2on_staged"),
+            libgit_root.path(b, "tests/resources/filemodes/exec_off2on_workdir"),
+            libgit_root.path(b, "tests/resources/filemodes/exec_on_untracked"),
+        }) |lazy| {
+            const path = lazy.getPath2(b, null);
+            const file = try std.fs.cwd().openFile(path, .{
+                .mode = .read_write,
+            });
+            defer file.close();
+            try file.setPermissions(.{ .inner = .{ .mode = 0o755 } });
+        }
+
         const gen_cmd = b.addSystemCommand(&.{"python"});
         gen_cmd.addFileArg(libgit_src.path("tests/clar/generate.py"));
         const clar_suite = gen_cmd.addPrefixedOutputDirectoryArg("-o", "clar_suite");