Why did my Git repo enter a detached HEAD state

Question

I ended up with a detached head today  the same problem as described in  git push says everything up-to-date even though I have local changes  As far as I know I didn t do anything out of the ordinary  just commits and pushes from my local repo     So how did I end up with a detached HEAD

User · Answer

It can easily happen if you try to undo changes you've made by re-checking-out files and not quite getting the syntax right.

You can look at the output of git log - you could paste the tail of the log here since the last successful commit, and we could all see what you did. Or you could paste-bin it and ask nicely in #git on freenode IRC.

User · Answer

Detached HEAD means that what s currently checked out is not a local branch     Some scenarios that will result in a Detached HEAD state    If you checkout a remote branch  say origin master  This is a read-only branch  Thus  when creating a commit from origin master it will be free-floating  i e  not connected to any branch  If you checkout a specific tag or commit  When doing a new commit from here  it will again be free-floating  i e  not connected to any branch  Note that when a branch is checked out  new commits always gets automatically placed at the tip    When you want to go back and checkout a specific commit or tag to start working from there  you could create a new branch originating from that commit and switch to it by git checkout -b new branch name  This will prevent the Detached HEAD state as you now have a branch checked out and not a commit

User · Answer

It can happen if you have a tag named same as a branch    Example  if  release 0 1  is tag name  then  git checkout release 0 1   produces detached HEAD at  release 0 1   If you expect release 0 1 to be a branch name  then you get confused

User · Answer

try   git reflog    this gives you a history of how your HEAD and branch pointers where moved in the past   e g     88ea06b HEAD  0   checkout  moving from DEVELOPMENT to remotes origin SomeNiceFeature e47bf80 HEAD  1   pull origin DEVELOPMENT  Fast-forward  the top of this list is one reasone one might encounter a DETACHED HEAD state     checking out a remote tracking branch

User · Answer

Any checkout of a commit that is not the name of one of your branches will get you a detached HEAD  A SHA1 which represents the tip of a branch still gives a detached HEAD  Only a checkout of a local branch name avoids that mode  See committing with a detached HEAD  When HEAD is detached  commits work like normal  except no named branch gets updated   You can think of this as an anonymous branch     For example  if you checkout a  quot remote branch quot  without tracking it first  you can end up with a detached HEAD  See git  switch branch without detaching head Meaning  git checkout origin main  or origin master in the old days  would result in  Note  switching to  origin main    You are in  detached HEAD  state  You can look around  make experimental changes and commit them  and you can discard any commits you make in this state without impacting any branches by switching back to a branch   If you want to create a new branch to retain commits you create  you may do so  now or later  by using -c with the switch command  Example     git switch -c  lt new-branch-name gt   Or undo this operation with     git switch -  Turn off this advice by setting config variable advice detachedHead to false  HEAD is now at a1b2c3d My commit message  That is why you should not use git checkout anymore  but the new git switch command  With git switch  the same attempt to  quot checkout quot   switch to  a remote branch would fail immediately  git switch origin main fatal  a branch is expected  got remote branch  origin main    To add more on git switch  With Git 2 23  August 2019   you don t have to use the confusing git checkout command anymore  git switch can also checkout a branch  and get a detach HEAD  except   it has an explicit --detach option   To check out commit HEAD 3 for temporary inspection or experiment without creating a new branch  git switch --detach HEAD 3 HEAD is now at 9fc9555312 Merge branch  cc shared-index-permbits     it cannot detached by mistake a remote tracking branch  See  C  Users vonc arepo gt git checkout origin master Note  switching to  origin master    You are in  detached HEAD  state  You can look around  make experimental changes and commit them  and you can discard any commits you make in this state without impacting any branches by switching back to a branch   Vs  using the new git switch command  C  Users vonc arepo gt git switch origin master fatal  a branch is expected  got remote branch  origin master   If you wanted to create a new local branch tracking a remote branch  git switch  lt branch gt     If  lt branch gt  is not found but there does exist a tracking branch in exactly one remote  call it  lt remote gt   with a matching name  treat as equivalent to git switch -c  lt branch gt  --track  lt remote gt   lt branch gt    No more mistake  No more unwanted detached HEAD

User · Answer

When you checkout to a commit git checkout  lt commit-hash gt  or to a remote branch your HEAD will get detached and try to create a new commit on it   Commits that are not reachable by any branch or tag will be garbage collected and removed from the repository after 30 days   Another way to solve this is by creating a new branch for the newly created commit and checkout to it  git checkout -b  lt branch-name gt   lt commit-hash gt   This article illustrates how you can get to detached HEAD state

User · Answer

I reproduced this just now by accident    lists the remote branches  git branch -r       origin Feature f1234       origin master  I want to checkout one locally  so I cut paste   git checkout origin Feature f1234  Presto  Detached HEAD state  You are in  detached HEAD  state              Solution  1   Do not include origin  at the front of my branch spec when checking it out    git checkout Feature f1234   Solution  2   Add -b parameter which creates a local branch from the remote  git checkout -b origin Feature f1234  or  git checkout -b Feature f1234 it will fall back to origin automatically

User · Answer

If git was to rename detached HEAD I would have it named as a HEAD that isn   t identified by a branch and will soon be forgotten  We as people can easily remember branch names  We do git checkout new-button-feature   git checkout main  main and new-button-feature are easy to remember  And we can just do git branch and get a list of all branches  But to do the same with just commits you d have to do git reflog which is very tedious  Because you have thousands of commits but only very few branches  A detached commit   s identifier is just its SHA  So suppose you checked out a commit  not a branch  i e  you did git checkout d747dd10e450871928a56c9cb7c6577cf61fdf31 you ll get   Note  checking out  d747dd10e450871928a56c9cb7c6577cf61fdf31   You are in  detached HEAD  state       Then if you made some changes and made a commit  you re still NOT on a branch  Do you think you d remember the commit SHA  You won t  git doesn t want this to happen  Hence it s informing your HEAD is not associated to a branch so you re more inclined to checkout a new branch  As a result below that message it also says   If you want to create a new branch to retain commits you create  you may do so  now or later  by using -b with the checkout command again  Example  git checkout -b    To go a bit deeper a branch is built in a way that it s smart  It will update its HEAD as you make commits  Tags on the other hand are not meant to be like that  If you checkout a tag  then you re again on a detached HEAD  The main reason is that if you make a new commit from that tag then given that that commit is not referenced by anything  not any branch or tag  then still its considered a detached HEAD  Attached HEADs can only happen when you re on a branch  For more see here  HEAD is a pointer  and it points     directly or indirectly     to a particular commit  Attached  HEAD means that it is attached to some branch  i e  it points to a branch   Detached HEAD means that it is not attached to any branch  i e  it points directly to some commit   To look at from another angle  if you re on a branch and do cat  git HEAD you d get  ref  refs heads Your-current-branch-name  Then if you do cat refs heads Your-current-branch-name then you d also see the commit that your branch is pointing referencing to  However if you were on a detached HEAD you and cat  git HEAD you d just get the SHA of the commit and nothing more  639ce5dd952a645b7c3fcbe89e88e3dd081a9912  By nothing more I mean the head isn t pointing to any branch  It s just directly pointing to a commit   As a result of all this  anytime you checkout a commit  even if that commit was the latest commit of your main branch  you re still in a detached HEAD because your HEAD is not pointing to any branches  Hence even checking out a tag is will put you in a detached HEAD  Special thanks to Josh Caswell  amp  Saagar Jha in helping me figure this out

User · Answer

A simple accidental way is to do a git checkout head as a typo of HEAD   Try this   git init touch Readme md git add Readme md git commit git checkout head   which gives  Note  checking out  head    You are in  detached HEAD  state  You can look around  make experimental changes and commit them  and you can discard any commits you make in this state without impacting any branches by performing another checkout   If you want to create a new branch to retain commits you create  you may do so  now or later  by using -b with the checkout command again  Example     git checkout -b  lt new-branch-name gt   HEAD is now at 9354043    Readme

User · Answer

The other way to get in a git detached head state is to try to commit to a remote branch   Something like   git fetch git checkout origin foo vi bar git commit -a -m  changed bar    Note that if you do this  any further attempt to checkout origin foo will drop you back into a detached head state   The solution is to create your own local foo branch that tracks origin foo  then optionally push   This probably has nothing to do with your original problem  but this page is high on the google hits for  git detached head  and this scenario is severely under-documented

[git] Why did my Git repo enter a detached HEAD state?

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