Add Find The Initial Commit as a git til

git/find-the-initial-commit.md

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+# Find The Initial Commit
+
+By definition, the initial commit in a repository has no parents. You can
+exploit that fact and use `rev-list` to find the initial commit; a commit
+with no parents.
+
+```bash
+$ git rev-list --max-parents=0 HEAD
+```
+
+The `rev-list` command lists all commits in reverse chronological order. By
+restricting them to those with at most 0 parents, you are only going to get
+root commits. Generally, a repository will only have a single root commit,
+but it is possible for there to be more than one.
+
+See `man git-rev-list` for more details.