g.extension: sparse checkout with history for fast commit log access

[ninsbl]

git -log -1 is slow with sparse checkout if --filter=tree:0 is used because history is not checked out. Cloning is similarly fast with --filter=blob:none but then the history is checked out too and git log -1 should be fast again.

Please try e.g.:

dirs="src/raster/r.centroids src/imagery/i.pysptools.unmix"
cd /tmp
time (git clone -q --no-checkout --branch=grass8 --filter=blob:none https://github.com/osgeo/grass-addons
cd grass-addons
git sparse-checkout set $dirs
git checkout grass8)

cd grass-addons
for dir in $dirs
do
  time git log --first-parent -1 $dir
  
done
cd ..
rm -rf grass-addons

Fixes #2979

I marked this as blocker as 30 seconds wait time per addon is a pretty bad user experience. Feel free to remove the label if you disagree...

[tmszi]

Tested and works as expected.

This code line required changes too.

grass/utils/mkhtml.py

Line 712 in 2ca49e6

"--filter=tree:0",

Small note:

With blob:none change size of downloaded data from 2.6M to 6.5M.

[ninsbl]

Tested and works as expected.

This code line required changes too.

grass/utils/mkhtml.py

Line 712 in 2ca49e6

"--filter=tree:0",

Thanks for testing and pointing out the missing change in mkhtml.py... Addressed in 48a86df.

[ninsbl]

Cannot be backported to 8.2 directly, should be added to a bunch of g.extension-fixes that should be backported...