test(gitdb): generate standalone packed and loose object fixtures

GitDB tests previously opened the source checkout's `.git` directory or
`GITDB_TEST_GIT_REPO_BASE`, making their input depend on clone history.
Give each test class a disposable repository generated by a fixture
script, with packed history and additional loose objects. Isolate Git
configuration and identity during setup and register class cleanup.

Run the script with Bash so the standalone suite retains Python 3.8
support without adding a GixPython dependency. Remove the history override
and full-depth checkout from dependency CI, remove source `.git` before
running the suite, and document the new setup.
Use the actual database size when writing a pack instead of the unrelated
iteration count, which the smaller fixture exposed.

Validation: the GitDB suite passes from a source copy without `.git`
on Python 3.12/macOS: 24 passed, 1 skipped. The same source copy also
passes all 9 smmap tests. ShellCheck passes for the new fixture script.

Agent-Model: gpt-6-astra

Author: codex

.github/workflows/dependencies.yml

@@ -30,7 +30,6 @@ jobs:
     steps:
     - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
       with:
-        fetch-depth: 0
         persist-credentials: false
     - uses: actions/setup-python@6d4fd22b20465ccc0f7354476588e8df7c9ca0e0 # v7.1.0
       with:
@@ -45,8 +44,9 @@ jobs:
       run: flake8 "$PROJECT/$PROJECT" --count --select=E9,F63,F7,F82 --show-source --statistics
     - name: Test
       run: |
+        rm -rf .git
         if test "$PROJECT" = gitdb; then
-          GITDB_TEST_GIT_REPO_BASE="$(git rev-parse --git-common-dir)" pytest -o addopts= -v gitdb/gitdb/test
+          pytest -o addopts= -v gitdb/gitdb/test
         else
           pytest -o addopts= -v smmap/smmap/test
         fi

gitdb/README.rst

@@ -42,6 +42,9 @@ The source is available in the GitPython repository on GitHub:
 
 https://github.com/gitpython-developers/GitPython/tree/main/gitdb
 
+Tests require Git and Bash. Each test class gets a temporary repository generated
+from scratch with packed and loose objects; no source checkout history is needed.
+
 Run the tests with::
 
  pytest

gitdb/gitdb/test/fixtures/repository.sh

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+set -eu
+git init -q --object-format=sha1 -b main repo
+cd repo
+for n in $(seq 1 30); do
+    printf 'revision %s\n' "$n" >> file
+    git add file
+    git commit -qm "Revision $n"
+done
+git gc --prune=now
+# Keep both packed and loose objects for the compound database and tutorial tests.
+printf 'loose object\n' > loose
+git add loose
+git commit -qm 'Add loose objects'

gitdb/gitdb/test/lib.py

@@ -17,7 +17,7 @@
 import shutil
 import os
 import gc
-import logging
+import subprocess
 from functools import wraps
 
 
@@ -30,28 +30,28 @@ class TestBase(unittest.TestCase):
 
     * gitrepopath
 
-     * read-only base path of the git source repository, i.e. .../git/.git
+     * base path of a generated repository containing packed and loose objects
     """
 
-    #{ Invvariants
-    k_env_git_repo = "GITDB_TEST_GIT_REPO_BASE"
-    #} END invariants
-
     @classmethod
     def setUpClass(cls):
         try:
             super().setUpClass()
         except AttributeError:
             pass
 
-        cls.gitrepopath = os.environ.get(cls.k_env_git_repo)
-        if not cls.gitrepopath:
-            logging.info(
-                "You can set the %s environment variable to a .git repository of your choice - defaulting to the gitdb repository", cls.k_env_git_repo)
-            ospd = os.path.dirname
-            cls.gitrepopath = os.path.join(ospd(ospd(ospd(__file__))), '.git')
-        # end assure gitrepo is set
-        assert cls.gitrepopath.endswith('.git')
+        temporary = tempfile.TemporaryDirectory(prefix="gitdb-fixture-")
+        cls.addClassCleanup(temporary.cleanup)
+        env = {key: value for key, value in os.environ.items() if not key.startswith('GIT_')}
+        env.update(
+            GIT_CONFIG_NOSYSTEM='1', GIT_CONFIG_GLOBAL=os.devnull,
+            GIT_AUTHOR_NAME='GitDB Tests', GIT_AUTHOR_EMAIL='tests@example.invalid',
+            GIT_COMMITTER_NAME='GitDB Tests', GIT_COMMITTER_EMAIL='tests@example.invalid',
+            GIT_AUTHOR_DATE='2001-01-01T00:00:00 +0000', GIT_COMMITTER_DATE='2001-01-01T00:00:00 +0000',
+        )
+        # Keep the standalone suite usable on Python 3.8 without GixPython.
+        subprocess.run(['bash', fixture_path('repository.sh')], cwd=temporary.name, env=env, check=True)
+        cls.gitrepopath = os.path.join(temporary.name, 'repo', '.git')
 
 
 #} END bases

gitdb/gitdb/test/performance/test_pack_streaming.py

@@ -52,7 +52,7 @@ def test_pack_writing(self):
               (ni, elapsed, ni / (elapsed or 1)), file=sys.stderr)
 
         st = time()
-        PackEntity.write_pack((pdb.stream(sha) for sha in pdb.sha_iter()), ostream.write, object_count=ni)
+        PackEntity.write_pack((pdb.stream(sha) for sha in pdb.sha_iter()), ostream.write, object_count=pdb.size())
         elapsed = time() - st
         total_kb = ostream.bytes_written() / 1000
         print(sys.stderr, "PDB Streaming: Wrote pack of size %i kb in %f s (%f kb/s)" %