When dealing with a code base, I'd like to see a kind of high-level map of its history, potentially of many branches at once. This is difficult when the history has lots of commits, as a series of commits in a single branch can easily fill up the screen.
Is there an easy way to view only branches and merges, such that all the commits within branches are hidden?
On the Log dialog, you can control which commits are shown by opening the "Walk Behavior" menu at the bottom of the dialog. There you can select "Compressed Graph".
cf. https://tortoisegit.org/docs/tortoisegit/tgit-dug-showlog.html
An alternative would be to open the TortoiseGit context menu in explorer on a versioned folder and select "Revision Graph" (you might need to hold the shift-key when opening the context menu). Maybe you also want to enable "Show branchings and mergings" in the view menu.
cf. https://tortoisegit.org/docs/tortoisegit/tgit-dug-revgraph.html