I didn't encounter Git until the end of high school and it wasn't until a few years later that I actually understood how to use it properly. One of the biggest things I missed was the power of .gitignore. This lead to many wayward bin/ and gen/ commits and unnecessarily large repositories.

Fast forward to the present predicament: bulk cleaning of past commits.

  1. Add the .gitignore file you should have way back when.
    Github .gitignore Collection
    Base OS .gitignore Sample 
    2. <li>
	Apply the new <code>.gitignore</code> rules to all commits:<br />
    
    <pre>git filter-branch --force --index-filter \

    'git ls-files -ci --exclude-from=/path/to/repository/.gitignore -z | xargs -0 git rm --cached'
    --prune-empty --tag-name-filter cat -- --all
    If Git does not allow you to use the .gitignore file from within the repository then you will need to copy it into a different directory, update the path in the sample, and re-run it.

    See Reference section below for details on the above code sample

    <li>
	Overwrite remote repository:<br />
    <code>git push origin --force --all</code>
</li>

<li>[<i>Optional</i>] Add Git alias to apply <code>.gitignore</code> changes in the future<br />
Open Git configuration file <code>vi ~/.gitconfig</code><br />
If the <code>alias</code> section does not exist, you will need to add it.
<pre>[alias]
    apply-gitignore = !git ls-files -ci --exclude-standard -z | xargs -0r git rm --cached</pre>
Save your changes

Reference:
Github Help: Purging a File from Repository History
stackoverflow: Applying .gitignore to Committed Files