For big repos and/or bad network connection. I used this when I didn't know that `git clone --sparse --filter=blob:none` exists

git-clone-stable

#!/bin/sh
set -eufo pipefail

cd "$(
	# TO-DO: use `tee` to make output visible to user
	git clone --depth=1 --filter=blob:none "$@" 2>&1 | \
	# `-n` is not needed if we rm `/p`
	sed -En "s/Cloning into (bare repository )?'(.+)'.../\2/p"
)"

is_done() {
	[ "$(git rev-parse --is-shallow-repository)" = false ]
}

# emulate `fetch --unshallow`, gradually

# assume commit_count > 1
i=2
echo 'Begin exponential fetch...'
# "binary search"
while git fetch --depth=$i; do
	i=$((i+i))
	is_done && exit || :
done

echo 'Fail: roll-back to last successful depth...'

i=$((i>>1))

if [ $i -gt 1 ]; then
	m=$((i>>1))
else
	m=1
fi

echo 'Begin linear/quadratic-ish fetch...'

max_fail="${GIT_FETCH_LIN_MAX_FAIL:-}"

# https://github.com/koalaman/shellcheck/issues/3067#issuecomment-3359293981
is_uint() {
	printf %d "$1" >/dev/null 2>&1 && [ "$1" -ge 0 ]
}

if ! is_uint "$max_fail"; then
	max_fail=4
fi

readonly max_fail

fails=0
while ! is_done; do
	i=$((i+m))
	if git fetch --depth=$i; then
		# speed-up
		m=$((m+1))
	else
		fails=$((fails+1))
		[ $fails -ge "$max_fail" ] && exit 3
		# rollback to last successful depth
		i=$((i-m))
		# back off a little
		m=$((m-1))
		# avoid re-shallowing
		[ $m -le 0 ] && break
	fi
done