How does origin HEAD get set

Question

I have a branch set up to track a ref in origin   git checkout  lt branchname gt  switches to that branch  and a git status will show me how far ahead or behind my branch is from origin  but I m surprised that origin HEAD still points at origin master  and not origin  lt branchname gt   So my question is  under what circumstances does origin HEAD get moved   EDIT   I appreciate the answers about how to move origin HEAD  but I m interested in what  organically  moves it  outside of me explicitly telling it to do so   For example  when I switch branches  git makes HEAD point at the branch I m checking out  so I m surprised that origin HEAD doesn t move in the same manner

User · Answer

What moves origin HEAD  organically     git clone sets it once to the spot where HEAD is on origin   it serves as the default branch to checkout after cloning with git clone    What does HEAD on origin represent    on bare repositories  often repositories    on servers     it serves as a marker for the default branch  because git clone uses it in such a way on non-bare repositories  local or remote   it reflects the repository   s current checkout   What sets origin HEAD    git clone fetches and sets it it would make sense if git fetch updates it like any other reference  but it doesn   t git remote set-head origin -a fetches and sets it   useful to update the local knowledge of what remote considers the    default branch       Trivia   origin HEAD can also be set to any other value without contacting the remote  git remote set-head origin  lt branch gt    I see no use-case for this  except for testing  unfortunately nothing is able to set HEAD on the remote older versions of git did not know which branch HEAD points to on the remote  only which commit hash it finally has  so it just hopefully picked a branch name pointing to the same hash

User · Answer

Disclaimer  this is an update to Cascabel s answer  which I m writing to save the curious some time  I tried in vain to replicate  in Git 2 0 1  the remote HEAD is ambiguous message that Cascabel mentions in his answer  so I did a bit of digging  by cloning https   github com git git and searching the log   It used to be that  Determining HEAD is ambiguous since it is done by comparing SHA1s   In the case of multiple matches we return refs heads master if it matches  else we return the first match we encounter  builtin-remote needs all matches returned to it  so add a flag for it to request such     Commit 4229f1fa325870d6b24fe2a4c7d2ed5f14c6f771  dated Feb 27  2009  found with git log --reverse --grep  quot HEAD is ambiguous quot   However  the ambiguity in question has since been lifted   One long-standing flaw in the pack transfer protocol used by  quot git clone quot  was that there was no way to tell the other end which branch  quot HEAD quot  points at  and the receiving end needed to guess   A new capability has been defined in the pack protocol to convey this information so that cloning from a repository with more than one branches pointing at the same commit where the HEAD is at now reliably sets the initial branch in the resulting repository     Commit 9196a2f8bd46d36a285bdfa03b4540ed3f01f671  dated Nov 8  2013  found with git log --grep  quot ambiguous quot  --grep  quot HEAD quot  --all-match  Edit  thanks to torek     git name-rev --name-only 9196a2f8bd46d36a285bdfa03b4540ed3f01f671 tags v1 8 4 3 3  This means that  if you re using Git v1 8 4 3 or later  you shouldn t run into any ambiguous-remote-HEAD problem

User · Answer

Remember there are two independent git repos we are talking about   Your local repo with your code and the remote running somewhere else   Your are right  when you change a branch  HEAD points to your current branch   All of this is happening on your local git repo   Not the remote repo  which could be owned by another developer  or siting on a sever in your office  or github  or another directory on the filesystem  or etc     Your computer  local repo  has no business changing the HEAD pointer on the remote git repo   It could be owned by a different developer for example   One more thing  what your computer calls origin XXX is your computer s understanding of the state of the remote at the time of the last fetch   So what would  organically  update origin HEAD   It would be activity on the remote git repo   Not your local repo   People have mentioned      git symbolic-ref HEAD refs head my other branch   Normally  that is used when there is a shared central git repo on a server for use by the development team   It would be a command executed on the remote computer   You would see this as activity on the remote git repo

User · Answer

It is your setting as the owner of your local repo  Change it like this   git remote set-head origin some branch   And origin HEAD will point to your branch instead of master  This would then apply to your repo only and not for others  By default  it will point to master  unless something else has been configured on the remote repo   Manual entry for remote set-head provides some good information on this   Edit  to emphasize  without you telling it to  the only way it would  move  would be a case like renaming the master branch  which I don t think is considered  organic   So  I would say organically it does not move

User · Answer

Note first that your question shows a bit of misunderstanding  origin HEAD represents the default branch on the remote  i e  the HEAD that s in that remote repository you re calling origin  When you switch branches in your repo  you re not affecting that  The same is true for remote branches  you might have master and origin master in your repo  where origin master represents a local copy of the master branch in the remote repository    origin s HEAD will only change if you or someone else actually changes it in the remote repository  which should basically never happen - you want the default branch a public repo to stay constant  on the stable branch  probably master   origin HEAD is a local ref representing a local copy of the HEAD in the remote repository   Its full name is refs remotes origin HEAD    I think the above answers what you actually wanted to know  but to go ahead and answer the question you explicitly asked    origin HEAD is set automatically when you clone a repository  and that s about it  Bizarrely  that it s not set by commands like git remote update - I believe the only way it will change is if you manually change it   By change I mean point to a different branch  obviously the commit it points to changes if that branch changes  which might happen on fetch pull remote update      Edit  The problem discussed below was corrected in Git 1 8 4 3  see this update     There is a tiny caveat  though  HEAD is a symbolic ref  pointing to a branch instead of directly to a commit  but the git remote transfer protocols only report commits for refs  So Git knows the SHA1 of the commit pointed to by HEAD and all other refs  it then has to deduce the value of HEAD by finding a branch that points to the same commit  This means that if two branches happen to point there  it s ambiguous   I believe it picks master if possible  then falls back to first alphabetically   You ll see this reported in the output of git remote show origin     git remote show origin   remote origin   Fetch URL        Push  URL        HEAD branch  remote HEAD is ambiguous  may be one of the following       foo     master   Oddly  although the notion of HEAD printed this way will change if things change on the remote  e g  if foo is removed   it doesn t actually update refs remotes origin HEAD  This can lead to really odd situations  Say that in the above example origin HEAD actually pointed to foo  and origin s foo branch was then removed  We can then do this     git remote show origin     HEAD branch  master   git symbolic-ref refs remotes origin HEAD refs remotes origin foo   git remote update --prune origin Fetching origin  x  deleted           none      - gt  origin foo     refs remotes origin HEAD has become dangling    So even though remote show knows HEAD is master  it doesn t update anything  The stale foo branch is correctly pruned  and HEAD becomes dangling  pointing to a nonexistent branch   and it still doesn t update it to point to master  If you want to fix this  use git remote set-head origin -a  which automatically determines origin s HEAD as above  and then actually sets origin HEAD to point to the appropriate remote branch

User · Answer

Run the following commands from git CLI     move to the wanted commit git reset --hard  lt commit-hash gt      update remote git push --force origin  lt branch-name gt

[git] How does origin/HEAD get set?

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