1Date: Sat, 13 Aug 2005 22:16:02 -0700 (PDT) 2From: Linus Torvalds <torvalds@osdl.org> 3To: Steve French <smfrench@austin.rr.com> 4cc: git@vger.kernel.org 5Subject: Re: sending changesets from the middle of a git tree 6Abstract: In this article, Linus demonstrates how a broken commit 7 in a sequence of commits can be removed by rewinding the head and 8 reapplying selected changes. 9 10On Sat, 13 Aug 2005, Linus Torvalds wrote: 11 12> That's correct. Same things apply: you can move a patch over, and create a 13> new one with a modified comment, but basically the _old_ commit will be 14> immutable. 15 16Let me clarify. 17 18You can entirely _drop_ old branches, so commits may be immutable, but 19nothing forces you to keep them. Of course, when you drop a commit, you'll 20always end up dropping all the commits that depended on it, and if you 21actually got somebody else to pull that commit you can't drop it from 22_their_ repository, but undoing things is not impossible. 23 24For example, let's say that you've made a mess of things: you've committed 25three commits "old->a->b->c", and you notice that "a" was broken, but you 26want to save "b" and "c". What you can do is 27 28 # Create a branch "broken" that is the current code 29 # for reference 30 git branch broken 31 32 # Reset the main branch to three parents back: this 33 # effectively undoes the three top commits 34 git reset HEAD^^^ 35 git checkout -f 36 37 # Check the result visually to make sure you know what's 38 # going on 39 gitk --all 40 41 # Re-apply the two top ones from "broken" 42 # 43 # First "parent of broken" (aka b): 44 git-diff-tree -p broken^ | git-apply --index 45 git commit --reedit=broken^ 46 47 # Then "top of broken" (aka c): 48 git-diff-tree -p broken | git-apply --index 49 git commit --reedit=broken 50 51and you've now re-applied (and possibly edited the comments) the two 52commits b/c, and commit "a" is basically gone (it still exists in the 53"broken" branch, of course). 54 55Finally, check out the end result again: 56 57 # Look at the new commit history 58 gitk --all 59 60to see that everything looks sensible. 61 62And then, you can just remove the broken branch if you decide you really 63don't want it: 64 65 # remove 'broken' branch 66 git branch -d broken 67 68 # Prune old objects if you're really really sure 69 git prune 70 71And yeah, I'm sure there are other ways of doing this. And as usual, the 72above is totally untested, and I just wrote it down in this email, so if 73I've done something wrong, you'll have to figure it out on your own ;) 74 75 Linus 76- 77To unsubscribe from this list: send the line "unsubscribe git" in 78the body of a message to majordomo@vger.kernel.org 79More majordomo info at http://vger.kernel.org/majordomo-info.html