git clone --depth 1 --branch <tag_name> <repo_url>

ssh-agent bash -c 'ssh-add /home/git/.ssh/key-filename; git $GIT_COMMAND'

Example:

ssh-agent bash -c 'ssh-add /home/git/.ssh/key-filename; git push'

Source: https://stackoverflow.com/questions/4565700/how-to-specify-the-private-ssh-key-to-use-when-executing-shell-command-on-git

1. mv a/submodule a/submodule_tmp
2. git submodule deinit -f – a/submodule
3. rm -rf .git/modules/a/submodule
4. git rm -f a/submodule # Note: a/submodule (no trailing slash)

   or, if you want to leave it in your working tree and have done step 0
5. git rm –cached a/submodule

3bis mv a/submodule_tmp a/submodule

Source: https://stackoverflow.com/questions/1260748/how-do-i-remove-a-submodule

git checkout -- <file>

Source: https://stackoverflow.com/questions/31281679/how-to-undo-local-changes-to-a-specific-file

Source: https://stackoverflow.com/questions/14075581/git-undo-all-uncommitted-or-unsaved-changes

git remote add -f b path/to/repo_b.git
git remote update
git diff master remotes/b/master
git remote rm b

Source: https://stackoverflow.com/questions/1968512/getting-the-difference-between-two-repositories