ci/github: install git before checking out the repository

The GitHub's CI workflow uses 'actions/checkout@v4' to checkout the
repository. This action defaults to using the GitHub REST API to obtain
the repository if the `git` executable isn't available.

The step to build Git in the GitHub workflow can be summarized as:

  ...
  - uses: actions/checkout@v4 #1
  - run: ci/install-dependencies.sh #2
  ...
  - run: sudo --preserve-env --set-home --user=builder ci/run-build-and-tests.sh #3
  ...

Step #1, clones the repository, since the `git` executable isn't present
at this step, it uses GitHub's REST API to obtain a tar of the
repository.

Step #2, installs all dependencies, which includes the `git` executable.

Step #3, sets up the build, which includes setting up meson in the meson
job. At this point the `git` executable is present.

This means while the `git` executable is present, the repository doesn't
contain the '.git' folder. To keep both the CI's (GitLab and GitHub)
behavior consistent and to ensure that the build is performed on a
real-world scenario, install `git` before the repository is checked out.
This ensures that 'actions/checkout@v4' will clone the repository
instead of using a tarball. We also update the package cache while
installing `git`, this is because some distros will fail to locate the
package without updating the cache.

Helped-by: Phillip Wood <phillip.wood123@gmail.com>
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

.github/workflows/main.yml

@@ -414,6 +414,20 @@ jobs:
     - name: prepare libc6 for actions
       if: matrix.vector.jobname == 'linux32'
       run: apt -q update && apt -q -y install libc6-amd64 lib64stdc++6
+    - name: install git in container
+      run: |
+        if command -v git
+        then
+          : # nothing to do
+        elif command -v apk
+        then
+          apk add --update git
+        elif command -v dnf
+        then
+          dnf -yq update && dnf -yq install git
+        else
+          apt-get -q update && apt-get -q -y install git
+        fi
     - uses: actions/checkout@v4
     - run: ci/install-dependencies.sh
     - run: useradd builder --create-home