Fetch commit by SHA from remote even if not attached to a branch — useful for e.g. force-pushed PRs whose earlier commits are no longer directly available

git-fetch-sha

#!/bin/bash
# by Jonas Berlin 2021 from https://gist.github.com/xkr47/a82d710092847a39901a563b22e82b4b
# 1. Place in e.g. $HOME/bin/git-fetch-sha
# 2. Run "git fetch-sha" for usage

set -e

remote="$1"
sha="$2"

if [ "$sha" -a $(echo "$sha" | egrep '^[0-9a-f]{40}$' | wc -l) != 1 ]; then
    echo ERROR: Need full 40-character SHA
    exit 2
fi

if [ "$remote" ]; then
    url="$(git remote get-url "$remote")"
fi

if [ $# != 2 -o ! "$url" -o ! "$sha" ]; then
    echo "usage: git fetch-sha <remote> <full-40-character-sha>"
    echo
    echo "example: git fetch-sha origin 0123456789abcdef0123456789abcdef01234567"
    exit 1
fi

git fetch-pack "$url" "$sha"

echo
echo "Success. You can now optionally connect the sha to a branch:"
echo
echo "  git branch foo $sha"