Git merge with force overwrite

Question

I have a branch called demo which I need to merge with master branch  I can get the desired result with following commands   git pull origin demo git checkout master git pull origin master git merge demo git push origin master   My only concern is  if there are any merge issues  I want to tell git to overwrite changes in master branch without giving me merge prompt  So basically changes in demo branch should automatically overwrite changes in master branch    I looked around there are multiple options but I don t want to take chances with merging

User · Answer

When I tried using -X theirs and other related command switches I kept getting a merge commit  I probably wasn t understanding it correctly  One easy to understand alternative is just to delete the branch then track it again   git branch -D  lt branch-name gt  git branch --track  lt branch-name gt  origin  lt branch-name gt    This isn t exactly a  merge   but this is what I was looking for when I came across this question  In my case I wanted to pull changes from a remote branch that were force pushed

User · Answer

You can try  ours  option in git merge      git merge branch -X ours      This option forces conflicting hunks to be auto-resolved cleanly by favoring our version  Changes from the other tree that do not conflict                  with our side are reflected to the merge result  For a binary file  the entire contents are taken from our side

User · Answer

These commands will help in overwriting code of demo branch into master git fetch --all  Pull Your demo branch on local git pull origin demo  Now checkout to master branch  This branch will be completely changed with the code on demo branch git checkout master  Stay in the master branch and run this command  git reset --hard origin demo  reset means you will be resetting current branch --hard is a flag that means it will be reset without raising any merge conflict origin demo will be the branch that will be considered to be the code that will forcefully overwrite current master branch The output of the above command will show you your last commit message on origin demo or demo branch  Then  in the end  force push the code on the master branch to your remote repo  git push --force

User · Answer

I had a similar issue  where I needed to effectively replace any file that had changes   conflicts with a different branch   The solution I found was to use git merge -s ours branch    Note that the option is -s and not -X  -s denotes the use of ours as a top level merge strategy  -X would be applying the ours option to the recursive merge strategy  which is not what I  or we  want in this case   Steps  where oldbranch is the branch you want to overwrite with newbranch    git checkout newbranch checks out the branch you want to keep git merge -s ours oldbranch merges in the old branch  but keeps all of our files  git checkout oldbranch checks out the branch that you want to overwrite get merge newbranch merges in the new branch  overwriting the old branch

User · Answer

This merge approach will add one commit on top of master which pastes in whatever is in feature  without complaining about conflicts or other crap     Before you touch anything  git stash git status   if anything shows up here  move it to your desktop   Now prepare master  git checkout master git pull   if there is a problem in this step  it is outside the scope of this answer   Get feature all dressed up  git checkout feature git merge --strategy ours master   Go for the kill  git checkout master git merge --no-ff feature

User · Answer

Not really related to this answer  but I d ditch git pull  which just runs git fetch followed by git merge   You are doing three merges  which is going to make your Git run three fetch operations  when one fetch is all you will need   Hence   git fetch origin     update all our origin   remote-tracking branches  git checkout demo           if needed -- your example assumes you re on it git merge origin demo       if needed -- see below  git checkout master git merge origin master  git merge -X theirs demo     but see below  git push origin master       again  see below   Controlling the trickiest merge  The most interesting part here is git merge -X theirs   As root545 noted  the -X options are passed on to the merge strategy  and both the default recursive strategy and the alternative resolve strategy take -X ours or -X theirs  one or the other  but not both    To understand what they do  though  you need to know how Git finds  and treats  merge conflicts   A merge conflict can occur within some file1 when the base version differs from both the current  also called local  HEAD  or --ours  version and the other  also called remote or --theirs  version of that same file   That is  the merge has identified three revisions  three commits   base  ours  and theirs   The  base  version is from the merge base between our commit and their commit  as found in the commit graph  for much more on this  see other StackOverflow postings    Git has then found two sets of changes   what we did  and  what they did    These changes are  in general  found on a line-by-line  purely textual basis   Git has no real understanding of file contents  it is merely comparing each line of text   These changes are what you see in git diff output  and as always  they have context as well   It s possible that things we changed are on different lines from things they changed  so that the changes seem like they would not collide  but the context has also changed  e g   due to our change being close to the top or bottom of the file  so that the file runs out in our version  but in theirs  they have also added more text at the top or bottom    If the changes happen on different lines   for instance  we change color to colour on line 17 and they change fred to barney on line 71   then there is no conflict  Git simply takes both changes   If the changes happen on the same lines  but are identical changes  Git takes one copy of the change   Only if the changes are on the same lines  but are different changes  or that special case of interfering context  do you get a modify modify conflict   The -X ours and -X theirs options tell Git how to resolve this conflict  by picking just one of the two changes  ours  or theirs   Since you said you are merging demo  theirs  into master  ours  and want the changes from demo  you would want -X theirs   Blindly applying -X  however  is dangerous   Just because our changes did not conflict on a line-by-line basis does not mean our changes do not actually conflict   One classic example occurs in languages with variable declarations   The base version might declare an unused variable   int i    In our version  we delete the unused variable to make a compiler warning go away   and in their version  they add a loop some lines later  using i as the loop counter   If we combine the two changes  the resulting code no longer compiles   The -X option is no help here since the changes are on different lines   If you have an automated test suite  the most important thing to do is to run the tests after merging   You can do this after committing  and fix things up later if needed  or you can do it before committing  by adding --no-commit to the git merge command   We ll leave the details for all of this to other postings     1You can also get conflicts with respect to  file-wide  operations  e g   perhaps we fix the spelling of a word in a file  so that we have a change   and they delete the entire file  so that they have a delete    Git will not resolve these conflicts on its own  regardless of -X arguments     Doing fewer merges and or smarter merges and or using rebase  There are three merges in both of our command sequences   The first is to bring origin demo into the local demo  yours uses git pull which  if your Git is very old  will fail to update origin demo but will produce the same end result    The second is to bring origin master into master   It s not clear to me who is updating demo and or master   If you write your own code on your own demo branch  and others are writing code and pushing it to the demo branch on origin  then this first-step merge can have conflicts  or produce a real merge   More often than not  it s better to use rebase  rather than merge  to combine work  admittedly  this is a matter of taste and opinion    If so  you might want to use git rebase instead   On the other hand  if you never do any of your own commits on demo  you don t even need a demo branch   Alternatively  if you want to automate a lot of this  but be able to check carefully when there are commits that both you and others  made  you might want to use git merge --ff-only origin demo  this will fast-forward your demo to match the updated origin demo if possible  and simply outright fail if not  at which point you can inspect the two sets of changes  and choose a real merge or a rebase as appropriate    This same logic applies to master  although you are doing the merge on master  so you definitely do need a master   It is  however  even likelier that you would want the merge to fail if it cannot be done as a fast-forward non-merge  so this probably also should be git merge --ff-only origin master   Let s say that you never do your own commits on demo   In this case we can ditch the name demo entirely   git fetch origin     update origin    git checkout master git merge --ff-only origin master    die  cannot fast-forward our master   git merge -X theirs origin demo    die  complex merge conflict   git push origin master   If you are doing your own demo branch commits  this is not helpful  you might as well keep the existing merge  but maybe add --ff-only depending on what behavior you want   or switch it to doing a rebase   Note that all three methods may fail  merge may fail with a conflict  merge with --ff-only may not be able to fast-forward  and rebase may fail with a conflict  rebase works by  in essence  cherry-picking commits  which uses the merge machinery and hence can get a merge conflict

[git] Git merge with force overwrite

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