Fix gix-url baseline script instead of taking ownership

Taking ownership of cloned files in the container only fixed one
failing test, `gix-url::baseline run`. This had been failing with a
git `safe.directory` error in the the gix-url `make_baseline.sh`
fixture script. That failure was also reproduced locally by
recursively `chown`ing the cloned files to another user (while
preserving write permissions for the first user via the group).

Because the tests shouldn't unnecessarily depend on starting out in
a repository (nor anything about the outer repository they start
in), this should probably be considered a test bug that is not
specific to the current container setup on CI that triggered it.

This commit undoes the `chown -R` step in the CI workflow that had
previously worked around this, and instead fixes it by having the
gix-url `make_baseline.sh` fixture script run its `git fetch-pack`
commands in a temporary repo created in a subdirectory of the
fixture directory (and deleted afterwards).

.github/workflows/ci.yml

@@ -180,12 +180,6 @@ jobs:
           apt-get install --no-install-recommends -y -- "${prerequisites[@]}"
         shell: bash
       - uses: actions/checkout@v4
-      - name: Take ownership of repo
-        # FIXME: Eliminate the need for this by improving the test suite not to rely on ownership
-        # of preexisting files, nor on whether, where, or how we are contained in a repo (except
-        # where gix-testtools checks ignores to suppress archives). Note that `safe.directory`
-        # isn't a fix, due to config and environment sanitization when running fixture scripts.
-        run: chown -R "$(whoami)" -- "$GITHUB_WORKSPACE"
       - uses: dtolnay/rust-toolchain@stable
         with:
           toolchain: stable-i686-unknown-linux-gnu  # Otherwise it may misdetect based on the amd64 kernel.

gix-url/tests/fixtures/make_baseline.sh

@@ -55,14 +55,21 @@ tests_windows+=("c:repo")
 tests_unix+=("${tests[@]}")
 tests_windows+=("${tests[@]}")
 
+# We will run `git fetch-pack` in this repo instead of the outer gitoxide repo,
+# for full isolation. This avoids assuming there *is* a gitoxide repo, and also
+# avoids `safe.directory` errors if the gitoxide repo has unusual ownership.
+git init -q temp-repo
+
 for url in "${tests_unix[@]}"
 do
   echo ";" # there are no `;` in the tested urls
-  git fetch-pack --diag-url "$url"
+  git -C temp-repo fetch-pack --diag-url "$url"
 done >git-baseline.unix
 
 for url in "${tests_windows[@]}"
 do
   echo ";" # there are no `;` in the tested urls
-  git fetch-pack --diag-url "$url"
+  git -C temp-repo fetch-pack --diag-url "$url"
 done >git-baseline.windows
+
+rm -rf temp-repo