Shallow clone - preprocess specfile correctly or fail

[praiskup]

Similar to: https://pagure.io/fedora-infra/rpmautospec/issue/227

In the original issue, rpmautospec failed to generate any src.rpm.
Nowadays it "succeeds" , which is good (sometimes), but it produces
misleading output:

git clone https://src.fedoraproject.org/rpms/git-cola.git --depth 1
cd git-cola
$ fedpkg srpm
...
Wrote: /tmp/git-cola/git-cola-4.8.1-1.fc42.src.rpm
bsdtar xf /tmp/git-cola/git-cola-4.8.1-1.fc42.src.rpm git-cola.spec
grep %changelog -A 10 git-cola.spec 
%changelog
## START: Generated by rpmautospec
* Fri Jun 04 2021 Python Maint <[email protected]> - 3.9-2
- Rebuilt for Python 3.10

* Fri Feb 19 2021 David Schwörer <[email protected]> - 3.9-1
- Update to 3.9

* Tue Jan 26 2021 Fedora Release Engineering <[email protected]> - 3.8-2
- Rebuilt for https://fedoraproject.org/wiki/Fedora_34_Mass_Rebuild

The history is lost ^^^, the period 2021-2024. There's also
a wrong release_number = 1. With a full-clone, the generated
src.rpm looks different:

- /tmp/git-cola/git-cola-4.8.1-1.fc42.src.rpm
+ /tmp/git-cola/git-cola-4.8.1-2.fc42.src.rpm

Please provide a tool for "preparing" Git repositories for shallow clones,
for example something like rpmautospec shallowize. Such a tool would update the
./changelog file (adding new entries) and Release: tag accordingly.

Then, add a detection mechanism for missing commits in shallow clones.
Such commits that-if the repo was --unshallow'ed- would affect the overall
shape of the spec file or %changelog.

And finally, if the missing commit is detected - ideally start failing again
(by default, with some --ignore-missing-commits-like option).