Scenario

I got a task to update a CSS class:

.component-name .container-name {
  padding: 10px;
}

By convention, I knew it should be in:

/path-to-component/scss/component-name.scss

When I opened the file, I found .component-name but no sign of .container-name.

The problem:

  • I had no idea what screen this was for (small company, no docs).
  • I couldn’t test it in the UI.
  • But I do know how CSS works 😉.

My gut said this task was obsolete and the code had already been removed. Time to prove it.

Step 1. Check the file history

git log -n20 --pretty=%H /path-to-component/scss/component-name.scss

That gave me the last 20 commit hashes touching this file.

commit-20__xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
commit-19__xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
commit-18__xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
commit-17__xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
commit-16__xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
...
commit-4__xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
commit-3__xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
commit-2__xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
commit-1__xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Step 2. Search commits for the class

Loop through those commits and grep for .container-name:

git log -n20 --pretty=%H /path-to-component/scss/component-name.scss | \
	while read gc; do git show "${gc}:/path-to-component/scss/component-name.scss" | grep -q 'container-name' && echo $gc; done | \
    head -n1

Result:

commit-16__xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

So commit-16 was the last time this code existed.

Step 3. Find where it got removed

If commit-16 had it, then commit-17 must be where it was deleted. Diffing the two confirmed it:

git diff commit-16__xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx...commit-17__xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx -- /path-to-component/scss/component-name.scss

And bingo 🎉 — I found the diff where .container-name was deleted.

Lesson learned

  • Using git show, grep, and diff, I can track when a code block was last present and exactly when it was removed.
  • This approach is especially handy in legacy projects where “tribal knowledge” is lost but Git has the answers.