Add a GitHub workflow to generate Git for Windows' Pacman package

Git for Windows uses MSYS2 as base system, and therefore the Git
binaries are bundled as Pacman package.

This workflow allows building the 64-bit version of this package (which
is called `mingw-w64-x86_64-git`).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

.github/workflows/git-artifacts.yml

@@ -0,0 +1,141 @@
+name: mingw-w64-x86_64-git
+
+on:
+  # This workflow can be triggered manually in the Actions tab, see
+  # https://github.blog/changelog/2020-07-06-github-actions-manual-triggers-with-workflow_dispatch/
+  - workflow_dispatch
+
+env:
+  HOME: "${{github.workspace}}\\home"
+  MSYSTEM: MINGW64
+  USERPROFILE: "${{github.workspace}}\\home"
+
+jobs:
+  bundle-artifacts:
+    runs-on: windows-latest
+    steps:
+      - name: Configure user
+        shell: bash
+        run:
+          USER_NAME="${{github.actor}}" &&
+          USER_EMAIL="${{github.actor}}@users.noreply.github.com" &&
+          mkdir "$HOME" &&
+          git config --global user.name "$USER_NAME" &&
+          git config --global user.email "$USER_EMAIL" &&
+          echo "PACKAGER=$USER_NAME <$USER_EMAIL>" >>$GITHUB_ENV
+      - name: Download git-sdk-64-build-installers
+        shell: bash
+        run: |
+          # Use Git Bash to download and unpack the artifact
+
+          ## Get artifact
+          urlbase=https://dev.azure.com/git-for-windows/git/_apis/build/builds
+          id=$(curl "$urlbase?definitions=29&statusFilter=completed&resultFilter=succeeded&\$top=1" |
+            jq -r '.value[0].id')
+          download_url=$(curl "$urlbase/$id/artifacts" |
+            jq -r '.value[] | select(.name == "git-sdk-64-build-installers").resource.downloadUrl')
+
+          curl -o artifacts.zip "$download_url"
+
+          ## Unpack artifact
+          unzip artifacts.zip
+      - name: Clone build-extra
+        shell: bash
+        run: |
+          d=git-sdk-64-build-installers/usr/src/build-extra &&
+          git clone --single-branch -b main https://github.com/git-for-windows/build-extra $d
+      - name: Generate bundle artifacts
+        shell: powershell
+        run: |
+          & .\git-sdk-64-build-installers\git-cmd.exe --command=usr\bin\bash.exe -lc @"
+            printf '#!/bin/sh\n\nexec /mingw64/bin/git.exe "`$@"\n' >/usr/bin/git &&
+            mkdir -p bundle-artifacts &&
+
+            git -c init.defaultBranch=main init --bare &&
+            git remote add -f origin https://github.com/git-for-windows/git &&
+            git fetch https://github.com/${{github.repository}} ${{github.ref}}:${{github.ref}} &&
+
+            tag_name=\"`$(git describe --match 'v[0-9]*' FETCH_HEAD)-`$(date +%Y%m%d%H%M%S)\" &&
+            echo \"prerelease-`${tag_name#v}\" >bundle-artifacts/ver &&
+            echo \"`${tag_name#v}\" >bundle-artifacts/display_version &&
+            echo \"`$tag_name\" >bundle-artifacts/next_version &&
+            git tag -m \"Snapshot build\" \"`$tag_name\" FETCH_HEAD &&
+            git bundle create bundle-artifacts/git.bundle origin/main..\"`$tag_name\" &&
+
+            sh -x /usr/src/build-extra/please.sh mention feature \"Snapshot of `$(git show -s  --pretty='tformat:%h (%s, %ad)' --date=short FETCH_HEAD)\" &&
+            git -C /usr/src/build-extra bundle create \"`$PWD/bundle-artifacts/build-extra.bundle\" origin/main..main
+          "@
+      - name: 'Publish Pipeline Artifact: bundle-artifacts'
+        uses: actions/upload-artifact@v1
+        with:
+          name: bundle-artifacts
+          path: bundle-artifacts
+  pkg-x86_64:
+    runs-on: windows-latest
+    needs: bundle-artifacts
+    steps:
+      - name: Configure user
+        shell: bash
+        run:
+          USER_NAME="${{github.actor}}" &&
+          USER_EMAIL="${{github.actor}}@users.noreply.github.com" &&
+          mkdir "$HOME" &&
+          git config --global user.name "$USER_NAME" &&
+          git config --global user.email "$USER_EMAIL" &&
+          echo "PACKAGER=$USER_NAME <$USER_EMAIL>" >>$GITHUB_ENV
+      - name: Download git-sdk-64-makepkg-git
+        shell: bash
+        run: |
+          # Use Git Bash to download and unpack the artifact
+
+          ## Get artifact
+          urlbase=https://dev.azure.com/git-for-windows/git/_apis/build/builds
+          id=${{ needs.bundle-artifacts.outputs.latest-sdk64-extra-build-id }}
+          download_url="$(curl "$urlbase/$id/artifacts" |
+            jq -r '.value[] | select(.name == "git-sdk-64-makepkg-git").resource.downloadUrl')"
+
+          curl -o artifacts.zip "$download_url"
+
+          ## Unpack artifact
+          unzip artifacts.zip
+      - name: Download bundle-artifacts
+        uses: actions/download-artifact@v1
+        with:
+          name: bundle-artifacts
+          path: bundle-artifacts
+      - name: Clone and update build-extra
+        shell: bash
+        run: |
+          d=git-sdk-64-makepkg-git/usr/src/build-extra &&
+          git clone --single-branch -b main https://github.com/git-for-windows/build-extra $d &&
+          git -C $d pull "$PWD"/bundle-artifacts/build-extra.bundle main
+      - name: Check out git/git
+        shell: bash
+        run: |
+          git -c init.defaultBranch=main init &&
+          git remote add -f origin https://github.com/git-for-windows/git &&
+          git fetch --tags bundle-artifacts/git.bundle $(cat bundle-artifacts/next_version) &&
+          git reset --hard $(cat bundle-artifacts/next_version)
+      - name: Build mingw-w64-x86_64-git
+        shell: powershell
+        run: |
+          & git-sdk-64-makepkg-git\usr\bin\sh.exe -lc @"
+            set -x
+            # Let `cv2pdb` find the DLLs
+            PATH=\"`$PATH:/c/Program Files/Microsoft Visual Studio/2022/Enterprise/Common7/IDE/:/C/Program Files (x86)/Microsoft Visual Studio 14.0/VC/bin/amd64\"
+            type -p mspdb140.dll || exit 1
+            sh -x /usr/src/build-extra/please.sh build-mingw-w64-git --only-64-bit --build-src-pkg -o artifacts HEAD &&
+            cp bundle-artifacts/ver artifacts/ &&
+
+            b=`$PWD/artifacts &&
+            version=`$(cat bundle-artifacts/next_version) &&
+            (cd /usr/src/MINGW-packages/mingw-w64-git &&
+            cp PKGBUILD.`$version PKGBUILD &&
+            git commit -s -m \"mingw-w64-git: new version (`$version)\" PKGBUILD &&
+            git bundle create \"`$b\"/MINGW-packages.bundle origin/main..main)
+          "@
+      - name: Publish mingw-w64-x86_64-git
+        uses: actions/upload-artifact@v1
+        with:
+          name: pkg-x86_64
+          path: artifacts