Finding things
Deep history, finished
A repository whose history is too large to walk inside one run used to be walked from the newest commit until the clock ran out, every night, for ever. The far end is where the credential somebody deleted years ago is still sitting.
A window, and a marker
A run covers so many days of history, newest first, records where it got to, and the next run carries on from there until the first commit is reached. After that only new commits are walked, which is cheap. The window is off by default, which keeps the single pass over everything for a repository that already finishes.
The front of the history as well
Working backwards is no reason to stop looking at what was pushed this week. A run walks two ranges: the window it is up to, and everything that has arrived since the last time that repository was looked at. Checked against a repository with commits spread over four hundred days, with another pushed while the walk was still working backwards: every commit is walked at least once, and the new one on the very next run rather than at the end.
The quiet hours
On a nightly schedule a window a night is slow. So every twenty minutes, if nothing else is scanning, the repositories furthest from the end of their history get another window. It refuses itself while any scan is running, because the point is to use time nobody wants rather than to compete with the run somebody arranged.
What each engine can cover
gitleaks takes git log options, so it walks any range and eventually covers a whole history. TruffleHog anchors at the recent end, so it takes the newest window each run. Deep history is therefore found but not proven live, and a finding already says which of the two it is.
What it does not do
Only worth turning on for a repository that does not finish. Set a window on an estate that already completes and every run does the same work in more passes.
Every feature page carries one of those. The comparison page scores the same ground against five products people pay for, including the rows that go against us.