Don't require empty clones directory

[m-aciek]

Clone/update repositories depending on presence (#150 (comment)).

Logs from a non-first run:

python generate.py 
INFO:root:starting at 2025-11-18 00:24:45.070584+00:00
venv already exists.
To recreate it, remove it first with `make clean-venv'.
mkdir -p build
Building NEWS from Misc/NEWS.d with blurb
[…]/pydocs-translation-dashboard/clones/cpython/Doc/build/NEWS is already up to date
PATH=./venv/bin:$PATH sphinx-build --builder gettext --doctree-dir build/doctrees --jobs auto  --doctree-dir build/doctrees-gettext  --fail-on-warning . build/gettext 
Running Sphinx v8.2.3
loading translations [en]... done
matplotlib is not installed, social cards will not be generated
loading pickled environment... done
building [gettext]: targets for 8 template files
[…]
build succeeded.

The message catalogs are in build/gettext.

failure: 3.14 sanketgarade/python-doc-mr: clone or switch
failure: 3.14 CuriousLearner/python-docs-hi-in: clone or switch
failure: 3.14 Abdur-rahmaanJ/python-docs-ar: clone or switch
failure: 3.14 revisto/python-docs-fa: clone or switch
failure: 3.14 python/python-docs-it: clone or switch
failure: 3.13 sanketgarade/python-doc-mr: clone or switch
failure: 3.13 Abdur-rahmaanJ/python-docs-ar: clone or switch
success: 3.14 python/python-docs-el: clone or switch
success: 3.14 python/python-docs-ko: clone or switch
success: 3.14 python/python-docs-bn-in: clone or switch
failure: 3.12 sanketgarade/python-doc-mr: clone or switch
failure: 3.12 Abdur-rahmaanJ/python-docs-ar: clone or switch
success: 3.13 revisto/python-docs-fa: clone or switch
success: 3.13 python/python-docs-it: clone or switch
success: 3.13 CuriousLearner/python-docs-hi-in: clone or switch
success: 3.14 python/python-docs-fr: clone or switch
failure: 3.11 Abdur-rahmaanJ/python-docs-ar: clone or switch
success: 3.14 python/python-docs-pt-br: clone or switch
failure: 3.11 sanketgarade/python-doc-mr: clone or switch
success: 3.14 python/python-docs-pl: clone or switch
success: 3.14 python/python-docs-id: clone or switch
success: 3.14 python/python-docs-hu: clone or switch
success: 3.14 python/python-docs-ja: clone or switch
failure: 3.10 sanketgarade/python-doc-mr: clone or switch
failure: 3.10 Abdur-rahmaanJ/python-docs-ar: clone or switch
failure: master sanketgarade/python-doc-mr: clone or switch
success: master Abdur-rahmaanJ/python-docs-ar: clone or switch
success: main sanketgarade/python-doc-mr: clone or switch
ERROR:root:Error merging clones/translations/python/python-docs-it/whatsnew/3.12.po. Replaced with clones/cpython/Doc/build/gettext/whatsnew/3.12.pot
Traceback (most recent call last):
[…]
OSError: Syntax error in po file clones/translations/python/python-docs-it/whatsnew/3.12.po (line 4361)
WARNING:root:No cache found
[…]
WARNING:root:No cache found
failure: 3.14 python/python-docs-es: clone or switch
success: 3.14 MLGRussianXP/python-docs-ru: clone or switch
success: 3.13 python/python-docs-es: clone or switch
success: 3.14 python/python-docs-zh-cn: clone or switch
success: 3.14 python/python-docs-sv: clone or switch
failure: 3.14 python/python-docs-tr: clone or switch
failure: 3.14 python/python-docs-uk: clone or switch
failure: 3.13 python/python-docs-tr: clone or switch
success: 3.13 python/python-docs-uk: clone or switch
success: 3.12 python/python-docs-tr: clone or switch
success: 3.14 python/python-docs-zh-tw: clone or switch

---

📊 Dashboard preview 📊: https://python-docs-translations.github.io/dashboard/153/merge/

[StanFromIreland]

We could run make ... clean?

[m-aciek]

Automatically? 🤔

[m-aciek]

Added the clean before: e4c4dbc