THIS is cool…if you use Photoshop
Of your a plumber, nothing to see here, move along

PS: Alter history in with Photoshop – No time machine needed!: "When you select a history state in the History palette and then change the image, all states below the active state are deleted/replaced. This stinks if you want to remove only a few things, but keep others.







If you enable the Allow Non-Linear History option (from the History Options in the History palette menu), you can select a state, make a change to the image, and the change will be appended to the bottom of the History palette (instead of replacing all the states below the active state). You can even delete a state without losing any of the states below it!



Note:The color of the horizontal lines between history states indicate their linearity. White dividers indicate linear states and black dividers indicate non-linear states.



Note:Non-linear history is very memory intensive, use wisely!

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(Via CreativeBits.)