How do I remove a big file wrongly committed in git

The command you are looking for is filter-branch. It allows you to permanently remove files from an enlistment. This blog has a great tutorial on how to remove problematic files from the repository

• http://dalibornasevic.com/posts/2-permanently-remove-files-and-folders-from-a-git-repository

You can do it using the git filter-branch command, like this :

git filter-branch --index-filter "git rm -rf --cached --ignore-unmatch path_to_file" HEAD

You can find more documentation here http://dalibornasevic.com/posts/2-permanently-remove-files-and-folders-from-a-git-repository

You can take this great script from David Underhill to remove the file from the git repository:

#!/bin/bash
set -o errexit

# Author: David Underhill
# Script to permanently delete files/folders from your git repository.  To use 
# it, cd to your repository's root and then run the script with a list of paths
# you want to delete, e.g., git-delete-history path1 path2

if [ $# -eq 0 ]; then
    exit 0
fi

# make sure we're at the root of git repo
if [ ! -d .git ]; then
    echo "Error: must run this script from the root of a git repository"
    exit 1
fi

# remove all paths passed as arguments from the history of the repo
files=$@
git filter-branch --index-filter "git rm -rf --cached --ignore-unmatch $files" HEAD

# remove the temporary history git-filter-branch otherwise leaves behind for a long time
rm -rf .git/refs/original/ && git reflog expire --all &&  git gc --aggressive --prune