zig build dist and distcheck for source tarballs

This moves the source tarball creation process into the Zig build system
and follows the autotools-standard naming conventions of `dist` and
`distcheck`.

The `dist` target creates a source tarball in the `PREFIX/dist`
directory. The tarball is named `ghostty-VERSION.tar.gz` as expected by
standard source tarball conventions.

The `distcheck` target does the same as `dist`, but also takes the
resulting tarball, extracts it, and runs tests on the extracted source
to verify the source tarball works as expected.

This commit also updates CI:

  1. Tagged releases now use the new `zig build distcheck` command.
  2. Tip releases now use the new `zig build dist` command.
  3. A new test build tests that source tarball generation works on
     every commit.

.github/workflows/release-tag.yml

@@ -77,9 +77,18 @@ jobs:
     needs: [setup]
     env:
       GHOSTTY_VERSION: ${{ needs.setup.outputs.version }}
+      ZIG_LOCAL_CACHE_DIR: /zig/local-cache
+      ZIG_GLOBAL_CACHE_DIR: /zig/global-cache
     steps:
       - uses: actions/checkout@v4
 
+      - name: Setup Cache
+        uses: namespacelabs/nscloud-cache-action@v1.2.0
+        with:
+          path: |
+            /nix
+            /zig
+
       - uses: cachix/install-nix-action@v30
         with:
           nix_path: nixpkgs=channel:nixos-unstable
@@ -91,8 +100,8 @@ jobs:
 
       - name: Create Tarball
         run: |
-          git archive --format=tgz --prefix="ghostty-${GHOSTTY_VERSION}/" -o "ghostty-${GHOSTTY_VERSION}.tar.gz" HEAD
-          git archive --format=tgz --prefix=ghostty-source/ -o ghostty-source.tar.gz HEAD
+          nix develop -c zig build distcheck
+          cp zig-out/dist/ghostty-${GHOSTTY_VERSION}.tar.gz .
 
       - name: Sign Tarball
         run: |
@@ -108,8 +117,6 @@ jobs:
           path: |-
             ghostty-${{ env.GHOSTTY_VERSION }}.tar.gz
             ghostty-${{ env.GHOSTTY_VERSION }}.tar.gz.minisig
-            ghostty-source.tar.gz
-            ghostty-source.tar.gz.minisig
 
   build-macos:
     needs: [setup]

.github/workflows/release-tip.yml

@@ -101,8 +101,17 @@ jobs:
         )
       }}
     runs-on: namespace-profile-ghostty-md
+    env:
+      ZIG_LOCAL_CACHE_DIR: /zig/local-cache
+      ZIG_GLOBAL_CACHE_DIR: /zig/global-cache
     steps:
       - uses: actions/checkout@v4
+      - name: Setup Cache
+        uses: namespacelabs/nscloud-cache-action@v1.2.0
+        with:
+          path: |
+            /nix
+            /zig
       - uses: cachix/install-nix-action@v30
         with:
           nix_path: nixpkgs=channel:nixos-unstable
@@ -111,12 +120,17 @@ jobs:
           name: ghostty
           authToken: "${{ secrets.CACHIX_AUTH_TOKEN }}"
       - name: Create Tarball
-        run: git archive --format=tgz --prefix=ghostty-source/ -o ghostty-source.tar.gz HEAD
+        run: |
+          rm -rf zig-out/dist
+          nix develop -c zig build distcheck
+          cp zig-out/dist/*.tar.gz ghostty-source.tar.gz
+
       - name: Sign Tarball
         run: |
           echo -n "${{ secrets.MINISIGN_KEY }}" > minisign.key
           echo -n "${{ secrets.MINISIGN_PASSWORD }}" > minisign.password
           nix develop -c minisign -S -m ghostty-source.tar.gz -s minisign.key < minisign.password
+
       - name: Update Release
         uses: softprops/action-gh-release@v2
         with:

.github/workflows/test.yml

@@ -11,6 +11,7 @@ jobs:
     runs-on: namespace-profile-ghostty-sm
     needs:
       - build-bench
+      - build-dist
       - build-flatpak
       - build-linux
       - build-linux-libghostty
@@ -209,6 +210,35 @@ jobs:
       - name: Test NixOS package build
         run: nix build .#ghostty
 
+  build-dist:
+    runs-on: namespace-profile-ghostty-md
+    needs: test
+    env:
+      ZIG_LOCAL_CACHE_DIR: /zig/local-cache
+      ZIG_GLOBAL_CACHE_DIR: /zig/global-cache
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Setup Cache
+        uses: namespacelabs/nscloud-cache-action@v1.2.0
+        with:
+          path: |
+            /nix
+            /zig
+
+      # Install Nix and use that to run our tests so our environment matches exactly.
+      - uses: cachix/install-nix-action@v30
+        with:
+          nix_path: nixpkgs=channel:nixos-unstable
+      - uses: cachix/cachix-action@v15
+        with:
+          name: ghostty
+          authToken: "${{ secrets.CACHIX_AUTH_TOKEN }}"
+
+      - name: Build and Check Source Tarball
+        run: nix develop -c zig build distcheck
+
   build-macos:
     runs-on: namespace-profile-ghostty-macos
     needs: test