Squash the first two commits in Git

Question

With git rebase --interactive  lt commit gt  you can squash any number of commits together into a single one   That s all great unless you want to squash commits into the initial commit  That seems impossible to do   Are there any ways to achieve it     Moderately related   In a related question  I managed to come up with a different approach to the need of squashing against the first commit  which is  well  to make it the second one   If you re interested  git  how to insert a commit as the first  shifting all the others

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You could use rebase interactive to modify the last two commits before they ve been pushed to a remote  git rebase HEAD   -i

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You can use git filter-branch for that   e g   git filter-branch --parent-filter    if test  GIT COMMIT     lt sha1ofB gt   then cat  fi    This results in AB-C throwing away the commit log of A

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There is an easier way to do this   Let s assume you re on the master branch  Create a new orphaned branch which will remove all commit history     git checkout --orphan new branch   Add your initial commit message     git commit -a   Get rid of the old unmerged master branch     git branch -D master   Rename your current branch new branch to master     git branch -m master

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Squashing the first and second commit would result in the first commit being rewritten  If you have more than one branch that is based off the first commit  you d cut off that branch   Consider the following example   a---b---HEAD            ---d   Squashing a and b into a new commit  ab  would result in two distinct trees which in most cases is not desirable since git-merge and git-rebase will no longer work across the two branches   ab---HEAD  a---d   If you really want this  it can be done  Have a look at git-filter-branch for a powerful  and dangerous  tool for history rewriting

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Update July 2012  git 1 7 12    You now can rebase all commits up to root  and select the second commit Y to be squashed with the first X   git rebase -i --root master  pick sha1 X squash sha1 Y pick sha1 Z    git rebase  -i  --root  tip       This command can now be used to rewrite all the history leading from   tip  down to the root commit    See commit df5df20c1308f936ea542c86df1e9c6974168472 on GitHub from Chris Webb  arachsys      Original answer  February 2009   I believe you will find different recipes for that in the SO question  How do I combine the first two commits of a git repository    Charles Bailey provided there the most detailed answer  reminding us that a commit is a full tree  not just diffs from a previous states   And here the old commit  the  initial commit   and the new commit  result of the squashing  will have no common ancestor  That mean you can not  commit --amend  the initial commit into new one  and then rebase onto the new initial commit the history of the previous initial commit  lots of conflicts    That last sentence is no longer true with git rebase -i --root  lt aBranch gt    Rather  with A the original  initial commit   and B a subsequent commit needed to be squashed into the initial one     Go back to the last commit that we want to form the initial commit  detach HEAD    git checkout  lt sha1 for B gt   Reset the branch pointer to the initial commit  but leaving the index and working tree intact   git reset --soft  lt sha1 for A gt   Amend the initial tree using the tree from  B    git commit --amend  Temporarily tag this new initial commit  or you could remember the new commit sha1 manually    git tag tmp  Go back to the original branch  assume master for this example    git checkout master  Replay all the commits after B onto the new initial commit   git rebase --onto tmp  lt sha1 for B gt   Remove the temporary tag   git tag -d tmp    That way  the  rebase --onto  does not introduce conflicts during the merge  since it rebases history made after the last commit  B  to be squashed into the initial one  which was A  to tmp  representing the squashed new initial commit   trivial fast-forward merges only     That works for  A-B   but also  A-   -   -   -B   any number of commits can be squashed into the initial one this way

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For what it s worth  I avoid this problem by always creating a  no-op  first commit  in which the only thing in the repository is an empty  gitignore   https   github com DarwinAwardWinner git-custom-commands blob master bin git-myinit  That way  there s never any reason to mess with the first commit

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This will squash second commit into the first one   A-B-C-    - gt  AB-C-     git filter-branch --commit-filter       if     GIT COMMIT     lt sha1ofA gt         then         skip commit           else         git commit-tree           fi   HEAD   Commit message for AB will be taken from B  although I d prefer from A    Has the same effect as Uwe Kleine-K  nig s answer  but works for non-initial A as well

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If you simply want to squash all commits into a single  initial commit  just reset the repository and amend the first commit   git reset hash-of-first-commit git add -A git commit --amend   Git reset will leave the working tree intact  so everything is still there  So just add the files using git add commands  and amend the first commit with these changes  Compared to rebase -i you ll lose the ability to merge the git comments though

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I ve reworked VonC s script to do everything automatically and not ask me for anything  You give it two commit SHA1s and it will squash everything between them into one commit named  squashed history       bin sh   Go back to the last commit that we want   to form the initial commit  detach HEAD  git checkout  2    reset the branch pointer to the initial commit     1     but leaving the index and working tree intact  git reset --soft  1    amend the initial tree using the tree from  2 git commit --amend -m  squashed history     remember the new commit sha1 TARGET  git rev-list HEAD --max-count 1     go back to the original branch  assume master for this example  git checkout master    Replay all the commits after  2 onto the new initial commit git rebase --onto  TARGET  2

[git] Squash the first two commits in Git?

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