HEAD and ORIG HEAD in Git

Question

What do these symbols refer to and what do they mean     I can t find any explanation in official documentation

User · Answer

My understanding is that HEAD points the current branch, while ORIG_HEAD is used to store the previous HEAD before doing "dangerous" operations.

For example git-rebase and git-am record the original tip of branch before they apply any changes.

User · Answer

From git reset   quot pull quot  or  quot merge quot  always leaves the original tip of the current branch in ORIG HEAD  git reset --hard ORIG HEAD  Resetting hard to it brings your index file and the working tree back to that state  and resets the tip of the branch to that commit  git reset --merge ORIG HEAD  After inspecting the result of the merge  you may find that the change in the other branch is unsatisfactory  Running  quot git reset --hard ORIG HEAD quot  will let you go back to where you were  but it will discard your local changes  which you do not want   quot git reset --merge quot  keeps your local changes     Before any patches are applied  ORIG HEAD is set to the tip of the current branch  This is useful if you have problems with multiple commits  like running  git am  on the wrong branch or an error in the commits that is more easily fixed by changing the mailbox  e g   errors in the  quot From  quot  lines   In addition  merge always sets   git ORIG HEAD  to the original state of HEAD so a problematic merge can be removed by using  git reset ORIG HEAD     Note  from here  HEAD is a moving pointer   Sometimes it means the current branch  sometimes it doesn t  So HEAD is NOT a synonym for  quot current branch quot  everywhere already  HEAD means  quot current quot  everywhere in git  but it does not necessarily mean  quot current branch quot   i e  detached HEAD   But it almost always means the  quot current commit quot   It is the commit  quot git commit quot  builds on top of  and  quot git diff --cached quot  and  quot git status quot  compare against  It means the current branch only in very limited contexts  exactly when we want a branch name to operate on --- resetting and growing the branch tip via commit rebase etc    Reflog is a vehicle to go back in time and time machines have interesting interaction with the notion of  quot current quot   HEAD  5 minutes ago  could mean  quot dereference HEAD symref to find out what branch we are on RIGHT NOW  and then find out where the tip of that branch was 5 minutes ago quot   Alternatively it could mean  quot what is the commit I would have referred to as HEAD 5 minutes ago  e g  if I did  quot git show HEAD quot  back then quot     git1 8 4  July 2013  introduces introduced a new notation   Actually  it will be for 1 8 5  Q4 2013  reintroduced with commit 9ba89f4   by Felipe Contreras   Instead of typing four capital letters  quot HEAD quot   you can say  quot   quot  now  e g   quot git log   quot    See commit cdfd948  Typing  HEAD  is tedious  especially when we can use     instead  The reason for choosing     is that it follows naturally from the ref op syntax  e g  HEAD  u    except we have no ref  and no operation  and when we don t have those  it makes sens to assume  HEAD   So now we can use  git show   1   and all that goody goodness  Until now     was a valid name  but it conflicts with this idea  so let s make it invalid  Probably very few people  if any  used this name

User · Answer

HEAD is  direct or indirect  i e  symbolic  reference to the current commit  It is a commit that you have checked in the working directory  unless you made some changes  or equivalent   and it is a commit on top of which  quot git commit quot  would make a new one  Usually HEAD is symbolic reference to some other named branch  this branch is currently checked out branch  or current branch  HEAD can also point directly to a commit  this state is called  quot detached HEAD quot   and can be understood as being on unnamed  anonymous branch  And   alone is a shortcut for HEAD  since Git 1 8 5 ORIG HEAD is previous state of HEAD  set by commands that have possibly dangerous behavior  to be easy to revert them  It is less useful now that Git has reflog  HEAD  1  is roughly equivalent to ORIG HEAD  HEAD  1  is always last value of HEAD  ORIG HEAD is last value of HEAD before dangerous operation   For more information read git 1  manpage    gitrevisions 7  manpage  git-revisions   Git User s Manual  the Git Community Book and Git Glossary

User · Answer

From man 7 gitrevisions      HEAD names the commit on which you based the changes in the                  working tree   FETCH HEAD records the branch which you fetched                  from a remote repository with your last git fetch invocation                   ORIG HEAD is created by commands that move your HEAD in a                  drastic way  to record the position of the HEAD before their                  operation  so that you can easily change the tip of the branch                  back to the state before you ran them   MERGE HEAD records the                  commit s  which you are merging into your branch when you run                  git merge   CHERRY PICK HEAD records the commit which you are                  cherry-picking when you run git cherry-pick

[git] HEAD and ORIG_HEAD in Git

Examples related to git