Time travel with git


A thing about using git rebase is that it changes git history, and changing history is always risky (you’re not a Time Lord or a time agent)

Occasionally, you mess up. Running git log gives you a messed up git history, with duplicated and/or missing commits, and multiple merges of the same branch, and blah… blah…

On the bright side, you are using git, and that gives you the power of a time traveler.

Saviors of the day: ‘git reflog’ and ‘git reset’

A good thing about git is that all your committed changes are never truly gone (This is not actually true, though: traceable commits (commits whose children link to a t least one reference) are always …traceable; but orphaned commits will be gone in around 2 weeks by default, and thus, you have around 2 weeks to save your lost work), and can be traced back using git reflog.

This is an example of what produced by git reflog.

07f84b9 [email protected]{0}: checkout: moving from master to demo
41b8897 [email protected]{1}: reset: moving to origin/master
a54fdd2 [email protected]{2}: checkout: moving from demo to master
07f84b9 [email protected]{3}: merge master: Merge made by the 'recursive' strategy.
11b3cff [email protected]{4}: reset: moving to origin/demo
a54fdd2 [email protected]{5}: merge master: Fast-forward
11b3cff [email protected]{6}: checkout: moving from master to demo
a54fdd2 [email protected]{7}: rebase -i (finish): returning to refs/heads/master
a54fdd2 [email protected]{8}: rebase -i (pick): Hotfix: Check for AssetsConfirmed required value
c2a2f45 [email protected]{9}: rebase -i (pick): Move checkEmptyField into a separate javascript utils file
11b3cff [email protected]{10}: rebase -i (start): checkout demo
41b8897 [email protected]{11}: rebase: aborting
11b3cff [email protected]{12}: rebase: checkout demo
41b8897 [email protected]{13}: checkout: moving from demo to master

In the above example, you can see all the actions you have been doing to your git tree, and all the references to all the HEAD’s that you have been on.

For example:

41b8897 [email protected]{1}: reset: moving to origin/master

means that you have called

git reset origin/master

which makes the current working directory points to 41b8897. The hash 41b8897 is what would be used for a git reset (in case you want to reset your current branch to that point of time)

`git reset` changes the current branch's address to another git commit.

For example, I am currently on demo, and want to point demo from wherever to the current origin/master, I can do either

git reset origin/master --hard


git reset 41b8897 --hard

Note: specifying --hard forces resetting the content of the current directory to the destination commit, not only the reference of the current branch

Official documentation: