Revert "Drop support for EOL Python 3.7"

This brings back Python 3.7 support (allowing it to be installed on
3.7, and testing on 3.7 on CI), even though 3.7 is end-of-life,
because support for 3.7 is not being dropped by GitPython yet, and
there is value in keeping the version ranges supported by GitPython
and gitdb consistent.

This reverts commit 875acb4.

Author: EliahKagan

.github/workflows/pythonpackage.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12"]
+        python-version: ["3.7", "3.8", "3.9", "3.10", "3.11", "3.12"]
         include:
           - experimental: false
           - python-version: "3.12"

setup.py

@@ -22,7 +22,7 @@
     zip_safe=False,
     install_requires=['smmap>=3.0.1,<6'],
     long_description="""GitDB is a pure-Python git object database""",
-    python_requires='>=3.8',
+    python_requires='>=3.7',
     # See https://pypi.python.org/pypi?%3Aaction=list_classifiers
     classifiers=[
         "Development Status :: 5 - Production/Stable",
@@ -35,6 +35,7 @@
         "Operating System :: MacOS :: MacOS X",
         "Programming Language :: Python",
         "Programming Language :: Python :: 3",
+        "Programming Language :: Python :: 3.7",
         "Programming Language :: Python :: 3.8",
         "Programming Language :: Python :: 3.9",
         "Programming Language :: Python :: 3.10",