How to delete all Git commits except the last five

Question

I have a very large Git repository which only contains binary files which are changed pretty often. Naturally the Git repository is much larger than the actual files in it. I don't really care about old history, I only need some of the newer history to be able to revert some wrong changes. So let's say I want to remove all commits except the last five.

Naturally I want to do this to keep the repository small so the removed commits must be purged completely from the repo.

And I want to do all this non-interactively with a single command (alias) or script. How can I do this?

Answer 1

Here's an rebase-last-five alias to get you started. It will recreate the current branch so only the most recent five commits are in the history. It's probably best to make this a script (git-rebase-last-five.sh) that is available in a directory on your PATH; Git will find and use scripts named git-....sh without the need for any special configuration. The script should do more error checking and handling than this simple alias.

$ git config --global alias.rebase-last-five '!b="$(git branch --no-color | cut -c3-)" ; h="$(git rev-parse $b)" ; echo "Current branch: $b $h" ; c="$(git rev-parse $b~4)" ; echo "Recreating $b branch with initial commit $c ..." ; git checkout --orphan new-start $c ; git commit -C $c ; git rebase --onto new-start $c $b ; git branch -d new-start ; git gc' 

CAVEAT EMPTOR: Do heed the warnings about changing history.

Check the man pages (git help <command> or online) for further information.

An example usage:

$ git --version git version 1.7.12.rc2.16.g034161a $ git log --all --graph --decorate --oneline * e4b2337 (HEAD, master) 9 * e508980 8 * 01927dd 7 * 75c0fdb 6 * 20edb42 5 * 1260648 4 * b3d6cc8 3 * 187a0ef 2 * e5d09cf 1 * 07bf1e2 initial $ git rebase-last-five  Current branch: master e4b2337ef33d446bbb48cbc86b44afc964ba0712 Recreating master branch with initial commit 20edb42a06ae987463016e7f2c08e9df10fd94a0 ... Switched to a new branch 'new-start' [new-start (root-commit) 06ed4d5] 5  1 file changed, 1 insertion(+)  create mode 100644 A First, rewinding head to replay your work on top of it... Applying: 6 Applying: 7 Applying: 8 Applying: 9 Deleted branch new-start (was 06ed4d5). Counting objects: 35, done. Delta compression using up to 2 threads. Compressing objects: 100% (15/15), done. Writing objects: 100% (35/35), done. Total 35 (delta 4), reused 0 (delta 0) $ git log --all --graph --decorate --oneline * a7fb54b (HEAD, master) 9 * 413e5b0 8 * 638a1ae 7 * 9949c28 6 * 06ed4d5 5 

Answer 2

Ok, if you want what I think you want (see my comment), I think this should work:

1. Create branch to save all the commits (and just in case):

   git branch fullhistory

2. While still on master, reset --hard to the commit you want to retain history from:

   git reset --hard HEAD~5

3. Now reset without --hard to the beginning of history, this should leave your workspace untouched, so it remains in HEAD~5 state.

   git reset --soft <first_commit>

4. So now you have empty history on master, and all the changes you need in the workspace. Just commit them.

   git commit -m "all the old changes squashed"

5. Now cherry-pick this 4 commits from fullhistory you want to have here:

   git cherry-pick A..B

Where A is older than B, and remember A is NOT included. So it should be parent of the oldest commit you want to include.