Double-click on a node in the graph; let's choose 1.35.

You should see lines like

tytso 1.1 /*
tytso 1.1  * pass2.c --- check directory structure
tytso 1.1  *

Suppose that you were trying to track down a bug in symlink handling. You know that the problem has something to do with a function with pass1_check in its name. To find this

Press "/" and notice that the focus is in the search window at the bottom. Type in "pass1_check" and press "Enter". That's not the right one; press "n". Press "n" exactly 3 more times.

That's the one you want. But you remember it being different so you would like to see what it was like before this.

Left-click on the line containing e2fsck_pass1_check_symlink.

Notice that the highlighted node in the graph is now the one corresponding to the line you just clicked. To see the changes for this revision,

Press "d".

Repeat the search process to find the call to e2fsck_pass1_check_symlink:

Press "/". Type in "pass1" and press Enter. Press "n". Left-click on the line with pass1 highlighted.