Merge update and pull Git branches without using checkouts

Question

I work on a project that has 2 branches  A and B  I typically work on branch A  and merge stuff from branch B  For the merging  I would typically do   git merge origin branchB   However  I would also like to keep a local copy of branch B  as I may occasionally check out the branch without first merging with my branch A  For this  I would do   git checkout branchB git pull git checkout branchA   Is there a way to do the above in one command  and without having to switch branch back and forth  Should I be using git update-ref for that  How

User · Answer

It is absolutely possible to do any merge, even non-fast forward merges, without git checkout. The worktree answer by @grego is a good hint. To expand on that:

cd local_repo
git worktree add _master_wt master
cd _master_wt
git pull origin master:master
git merge --no-ff -m "merging workbranch" my_work_branch
cd ..
git worktree remove _master_wt

You have now merged the local work branch to the local master branch without switching your checkout.

User · Answer

Enter git-forward-merge      Without needing to checkout destination  git-forward-merge  lt source gt   lt destination gt  merges source into destination branch    https   github com schuyler1d git-forward-merge  Only works for automatic merges  if there are conflicts you need to use the regular merge

User · Answer

As Amber said  fast-forward merges are the only case in which you could conceivably do this  Any other merge conceivably needs to go through the whole three-way merge  applying patches  resolving conflicts deal - and that means there need to be files around   I happen to have a script around I use for exactly this  doing fast-forward merges without touching the work tree  unless you re merging into HEAD   It s a little long  because it s at least a bit robust - it checks to make sure that the merge would be a fast-forward  then performs it without checking out the branch  but producing the same results as if you had - you see the diff --stat summary of changes  and the entry in the reflog is exactly like a fast forward merge  instead of the  reset  one you get if you use branch -f  If you name it git-merge-ff and drop it in your bin directory  you can call it as a git command  git merge-ff      bin bash   usage         echo  Usage  git merge-ff  lt branch gt   lt committish-to-merge gt   1 gt  amp 2     exit 1     merge ff         branch   1      commit   2       branch orig hash    git show-ref -s --verify refs heads  branch 2 gt   dev null       if      -ne 0    then         echo  Error  unknown branch  branch  1 gt  amp 2          usage     fi      commit orig hash    git rev-parse --verify  commit 2 gt   dev null       if      -ne 0    then         echo  Error  unknown revision  commit  1 gt  amp 2          usage     fi      if      git symbolic-ref HEAD      refs heads  branch     then         git merge  quiet --ff-only   commit      else         if      git merge-base  branch orig hash  commit orig hash        branch orig hash     then             echo  Error  merging  commit into  branch would not be a fast-forward  1 gt  amp 2             exit 1         fi         echo  Updating   branch orig hash 0 7     commit orig hash 0 7           if git update-ref -m  merge  commit  Fast forward   refs heads  branch    commit orig hash    branch orig hash   then             if   -z  quiet    then                 echo  Fast forward                  git diff --stat   branch  1     branch              fi         else             echo  Error  fast forward using update-ref failed  1 gt  amp 2         fi     fi    while getopts  q  opt  do     case  opt in         q   quiet  -q                       esac done shift    OPTIND-1    case    in     2    merge ff   1    2             usage esac   P S  If anyone sees any issues with that script  please comment  It was a write-and-forget job  but I d be happy to improve it

User · Answer

If you want to keep the same tree as one of the branch you want to merge  ie  not a real  merge    you can do it like this     Check if you can fast-forward if git merge-base --is-ancestor a b  then     git update-ref refs heads a refs heads b     exit fi    Else  create a  merge  commit commit    git commit-tree -p a -p b -m  merge b into a     git show -s --pretty format  T b       And update the branch to point to that commit git update-ref refs heads a   commit

User · Answer

The question is simple and the answer should be as simple  All the OP is asking is to merge the upstream origin branchB into his current branch without switching branches  TL DR  git fetch git merge origin branchB  The full answer  git pull does a fetch   merge  It s roughly the the same the two commands below  where  lt remote gt  is usually origin  default   and the remote tracking branch starts with  lt remote gt   followed by the remote branch name  git fetch   lt remote gt   git merge   u   The   u  notation is the configured remote tracking branch for the current branch  If branchB tracks origin branchB then   u  from branchB is the same as typing origin branchB  see git rev-parse --help for more info   Since you already merge with origin branchB  all that is missing is the git fetch  which can run from any branch  to update that remote-tracking branch  Note though that if there was any merge from the pull to include  you should rather merge branchB into branchA after having done a pull from branchB  and eventually push the changes to orign branchB   but as long as they re fast-forward they would remain the same  Keep in mind the local branchB will not be updated until you switch to it and do an actual pull  however as long as there are no local commits added to this branch it will just remain a fast-forward to the remote branch

User · Answer

git worktree add  -f   --detach   --checkout   --lock   -b  lt new-branch gt    lt path gt    lt commit-ish gt     You can try git worktree to have two branches open side by side  this sounds like it might be what you want but very different than some of the other answers I ve seen here   In this way you can have two separate branches tracking in the same git repo so you only have to fetch once to get updates in both work trees  rather than having to git clone twice and git pull on each   Worktree will create a new working directory for your code where you can have a different branch checked out simultaneously instead of swapping branches in place   When you want to remove it you can clean up with   git worktree remove  -f   lt worktree gt

User · Answer

just to pull the master without checking out the master I use   git fetch origin master master

User · Answer

You can simply git pull origin branchB into your branchA and git will do the trick for you

User · Answer

You can clone the repo and do the merge in the new repo  On the same filesystem  this will hardlink rather than copy most of the data   Finish by pulling the results into the original repo

User · Answer

Another  admittedly pretty brute way is to just re-create the branch   git fetch remote git branch -f localbranch remote remotebranch   This throws away the local outdated branch and re-creates one with the same name  so use with care

User · Answer

No  there is not  A checkout of the target branch is necessary to allow you to resolve conflicts  among other things  if Git is unable to automatically merge them   However  if the merge is one that would be fast-forward  you don t need to check out the target branch  because you don t actually need to merge anything - all you have to do is update the branch to point to the new head ref  You can do this with git branch -f  git branch -f branch-b branch-a  Will update branch-b to point to the head of branch-a  The -f option stands for --force  which means you must be careful when using it   Don t use it unless you are absolutely sure the merge will be fast-forward

User · Answer

For many cases  such as merging   you can just use the remote branch without having to update the local tracking branch  Adding a message in the reflog sounds like overkill and will stop it being quicker  To make it easier to recover  add the following into your git config   core      logallrefupdates true   Then type  git reflog show mybranch   to see the recent history for your branch

User · Answer

Another way to effectively do this is   git fetch git branch -d branchB git branch -t branchB origin branchB   Because it s a lower case -d  it will only delete it if the data will still exist somewhere  It s similar to  kkoehne s answer except it doesn t force  Because of the -t it will set up the remote again   I had a slightly different need than OP  which was to create a new feature branch off develop  or master   after merging a pull request  That can be accomplished in a one-liner without force  but it doesn t update the local develop branch  It s just a matter of checking out a new branch and having it be based off origin develop   git checkout -b new-feature origin develop

User · Answer

You can only do this if the merge is a fast-forward  If it s not  then git needs to have the files checked out so it can merge them   To do it for a fast-forward only   git fetch  lt branch that would be pulled for branchB gt  git update-ref -m  merge  lt commit gt   Fast forward  refs heads  lt branch gt   lt commit gt    where  lt commit gt  is the fetched commit  the one you want to fast-forward to  This is basically like using git branch -f to move the branch  except it also records it in the reflog as if you actually did the merge   Please  please  please don t do this for something that s not a fast-forward  or you ll just be resetting your branch to the other commit   To check  see if git merge-base  lt branch gt   lt commit gt  gives the branch s SHA1

User · Answer

The Short Answer As long as you re doing a fast-forward merge  then you can simply use git fetch  lt remote gt   lt sourceBranch gt   lt destinationBranch gt   Examples    Merge local branch foo into local branch master    without having to checkout master first    Here     means to use the local repository as the  quot remote quot   git fetch   foo master    Merge remote branch origin foo into local branch foo    without having to checkout foo first  git fetch origin foo foo  While Amber s answer will also work in fast-forward cases  using git fetch in this way instead is a little safer than just force-moving the branch reference  since git fetch will automatically prevent accidental non-fast-forwards as long as you don t use   in the refspec  The Long Answer You cannot merge a branch B into branch A without checking out A first if it would result in a non-fast-forward merge  This is because a working copy is needed to resolve any potential conflicts  However  in the case of fast-forward merges  this is possible  because such merges can never result in conflicts  by definition  To do this without checking out a branch first  you can use git fetch with a refspec  Here s an example of updating master  disallowing non-fast-forward changes  if you have another branch feature checked out  git fetch upstream master master  This use-case is so common  that you ll probably want to make an alias for it in your git configuration file  like this one   alias      sync    sh -c  git checkout --quiet HEAD  git fetch upstream master master  git checkout --quiet -   What this alias does is the following   git checkout HEAD  this puts your working copy into a detached-head state  This is useful if you want to update master while you happen to have it checked-out  I think it was necessary to do with because otherwise the branch reference for master won t move  but I don t remember if that s really right off-the-top of my head   git fetch upstream master master  this fast-forwards your local master to the same place as upstream master   git checkout - checks out your previously checked-out branch  that s what the - does in this case     The syntax of git fetch for  non- fast-forward merges If you want the fetch command to fail if the update is non-fast-forward  then you simply use a refspec of the form git fetch  lt remote gt   lt remoteBranch gt   lt localBranch gt   If you want to allow non-fast-forward updates  then you add a   to the front of the refspec  git fetch  lt remote gt    lt remoteBranch gt   lt localBranch gt   Note that you can pass your local repo as the  quot remote quot  parameter using    git fetch    lt sourceBranch gt   lt destinationBranch gt   The Documentation From the git fetch documentation that explains this syntax  emphasis mine     lt refspec gt  The format of a  lt refspec gt  parameter is an optional plus    followed by the source ref  lt src gt   followed by a colon    followed by the destination ref  lt dst gt   The remote ref that matches  lt src gt  is fetched  and if  lt dst gt  is not empty string  the local ref that matches it is fast-forwarded using  lt src gt   If the optional plus   is used  the local ref is updated even if it does not result in a fast-forward update   See Also  Git checkout and merge without touching working tree  Merging without changing the working directory

User · Answer

For many GitFlow users the most useful commands are  git fetch origin master master --update-head-ok git fetch origin dev dev --update-head-ok  The --update-head-ok flag allows using the same command while on dev or master branches  A handy alias in  gitconfig   alias      f  git fetch origin master master --update-head-ok  amp  amp  git fetch origin dev dev --update-head-ok

User · Answer

I wrote a shell function for a similar use case I encounter daily on projects  This is basically a shortcut for keeping local branches up to date with a common branch like develop before opening a PR  etc      Posting this even though you don t want to use checkout  in case others don t mind that constraint    glmh   git pull and merge here   will automatically checkout branchB  pull the latest  re-checkout branchA  and merge branchB   Doesn t address the need to keep a local copy of branchA  but could easily be modified to do so by adding a step before checking out branchB  Something like     git branch   branchA -no-branchB   branchA    For simple fast-forward merges  this skips to the commit message prompt   For non fast-forward merges  this places your branch in the conflict resolution state  you likely need to intervene    To setup  add  to  bashrc or  zshrc  etc   glmh         branchB  1          -eq 0    amp  amp    branchB  develop        branchA    git branch   grep       sed  s     g        git checkout   branchB   amp  amp  git pull     git checkout   branchA   amp  amp  git merge   branchB       Usage     No argument given  will assume  develop   gt  glmh    Pass an argument to pull and merge a specific branch  gt  glmh your-other-branch      Note  This is not robust enough to hand-off of args beyond branch name to git merge

User · Answer

In your case you can use  git fetch origin branchB branchB   which does what you want  assuming the merge is fast-forward   If the branch can t be updated because it requires a non-fast-forward merge  then this fails safely with a message   This form of fetch has some more useful options too   git fetch  lt remote gt   lt sourceBranch gt   lt destinationBranch gt    Note that  lt remote gt  can be a local repository  and  lt sourceBranch gt  can be a tracking branch  So you can update a local branch  even if it s not checked out  without accessing the network   Currently  my upstream server access is via a slow VPN  so I periodically connect  git fetch to update all remotes  and then disconnect  Then if  say  the remote master has changed  I can do  git fetch   remotes origin master master   to safely bring my local master up to date  even if I currently have some other branch checked out  No network access required

[git] Merge, update, and pull Git branches without using checkouts

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