Installation alternatives:

• Download git-timemachine.el and drop it somewhere in your load-path.
• If you use el-get, simply add git-timemachine to your packages list.
• If you have melpa configured it's available through package-install.

Visit a git-controlled file and issue M-x git-timemachine (or bind it to a keybinding of your choice). If you just need to toggle the time machine you can use M-x git-timemachine-toggle.

Use the following keys to navigate historic version of the file

• p Visit previous historic version
• n Visit next historic version
• w Copy the abbreviated hash of the current historic version
• W Copy the full hash of the current historic version
• g Goto nth revision
• t Goto revision by selected commit message
• i Show revision introducing text
• q Exit the time machine.
• b Run magit-blame on the currently visited revision (if magit available).
• c Show current commit using magit (if magit available).

Set git-timemachine-abbreviation-length (default 12) to your preferred length for abbreviated commit hashes.

Set git-timemachine-show-minibuffer-details (default t) to control whether details of the commit are shown in the minibuffer.

Also M-x customize [git-timemachine].

Just use your normal write-file and supply the file name of your choice. Be aware that you might be throwing away local uncommitted changes to the file in question. If you don't want to use you muscle memory to write the file you can map write-file to something short and sweet in git-timemachine-mode-map.

If you're having trouble using git-timemachine with native compilation turned on, possible together with a treesit enhanched mode such as python-ts-mode and get an error, try disabling native compilation for git-timemachine as it might help.