Re: Git Rebase Issue

[Christian Couder]

Hi,

On Tue, Dec 22, 2015 at 6:53 PM, Pierre-Luc Loyer
 wrote:
> Hi,
>
> I've encountered a situation using rebase for which I don't understand the 
> results, even after reading the documentation.
> I'm currently working in my feature branch and then I want to squash commits, 
> thus I use interactive rebase. After successfully completing the rebase, I 
> end up in a detached HEAD state, rather than back on my branch, which is 
> confusing. The command that is causing me to be in detached HEAD mode is: git 
> rebase -i HEAD~2 HEAD
> From the documentation, I read that my second parameter (HEAD) is the 
>  parameter:
>
>git rebase [-i | --interactive] [options] [--exec ] [--onto ]
>
>[] []
>
>If  is specified, git rebase will perform an automatic git 
> checkout  before doing anything else. Otherwise it remains on the 
> current branch.
>  Working branch; defaults to HEAD.
>
>Upon completion,  will be the current branch.
>
> Here is a full example than can be used to easily repro the issue. Go to an 
> empty folder.
> git init
> git echo text > file.txt
> git add .
> git commit -m "Add file.txt"
> git echo text2 > file.txt
> git commit -am "Modify file.txt"
> git echo text3 > file.txt
> git commit -am "Remodify file.txt"
>
> Now the interesting part:
> $ git rebase -i HEAD~2 HEAD
> [detached HEAD 9178b93] Modify file
> 1 file changed, 1 insertion(+), 1 deletion(-)
> Successfully rebased and updated detached HEAD.
>
> From the documentation it says that  (which is HEAD) will be checked 
> out before doing anything and that upon completion,  will be the 
> current branch. However, this doesn't seem to happen. In fact, it seems more 
> like the following is happening during the rebase:
> 1) detach HEAD
> 2) rebase
> 3) reattach to 
>
> If  is HEAD, then is does nothing and remains detached.
> I find this behavior confusing since I would expect it to return to whatever 
> HEAD was pointing to at the start of the command, such as my branch. Also, 
> the documentation says that the  parameter defaults to HEAD, so 
> passing 'HEAD' explicitly should result in the same behavior as not passing 
> it:
>  Working branch; defaults to HEAD.

You are right, it is probably a bug.
I guess usually people just use "git rebase -i HEAD~2" or "git rebase
-i master" and don't give the [] argument when using -i.

If you are interested in helping us debug this you might first want to
check if older git versions behaved like this.

Thanks,
Christian.
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Re: Git Rebase Issue

[Junio C Hamano]

Pierre-Luc Loyer  writes:

> From the documentation it says that  (which is HEAD) will be checked 
> out before doing anything and that upon completion,  will be the 
> current branch. However, this doesn't seem to happen. In fact, it seems more 
> like the following is happening during the rebase:
> 1) detach HEAD
> 2) rebase
> 3) reattach to 

You do not have to say "HEAD" for "", if you are rebasing
the current branch.  Either leave it unsaid, or name the branch.

Passing "HEAD" (or any of its variants that names the exact commit
at the tip of the current branch, without using the name of the
current branch, e.g. "master^0") as the "branch to rebase" is an
advanced technique to use when you want to avoid messing with the
branch itself.  It is deliberate that the HEAD is left detached.

You'd (once you learn Git sufficently and got comfortable with
working on a detached HEAD, that is) often find yourself doing
things like this:

1. rebase temporarily on detached HEAD

$ git rebase -i HEAD~2 HEAD ;# amend the tip two

2. double check the result and convince yourself that it is better
   than the original

$ git diff master HEAD

$ git log master.. >updated
$ git log -2 master >original
$ diff -u original updated

3-a. once satisfied, update the branch

$ git checkout -B master

3-b. or abandon if the result is undesirable.

$ git checkout master
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Git Rebase Issue

[Pierre-Luc Loyer]

Hi,

I've encountered a situation using rebase for which I don't understand the 
results, even after reading the documentation.
I'm currently working in my feature branch and then I want to squash commits, 
thus I use interactive rebase. After successfully completing the rebase, I end 
up in a detached HEAD state, rather than back on my branch, which is confusing. 
The command that is causing me to be in detached HEAD mode is: git rebase -i 
HEAD~2 HEAD
>From the documentation, I read that my second parameter (HEAD) is the  
>parameter:

   git rebase [-i | --interactive] [options] [--exec ] [--onto ]

   [] []

   If  is specified, git rebase will perform an automatic git checkout 
 before doing anything else. Otherwise it remains on the current branch.
 Working branch; defaults to HEAD.

   Upon completion,  will be the current branch.

Here is a full example than can be used to easily repro the issue. Go to an 
empty folder.
git init
git echo text > file.txt
git add .
git commit -m "Add file.txt"
git echo text2 > file.txt
git commit -am "Modify file.txt"
git echo text3 > file.txt
git commit -am "Remodify file.txt"

Now the interesting part:
$ git rebase -i HEAD~2 HEAD
[detached HEAD 9178b93] Modify file
1 file changed, 1 insertion(+), 1 deletion(-)
Successfully rebased and updated detached HEAD. 

>From the documentation it says that  (which is HEAD) will be checked 
>out before doing anything and that upon completion,  will be the 
>current branch. However, this doesn't seem to happen. In fact, it seems more 
>like the following is happening during the rebase:
1) detach HEAD
2) rebase
3) reattach to 

If  is HEAD, then is does nothing and remains detached.
I find this behavior confusing since I would expect it to return to whatever 
HEAD was pointing to at the start of the command, such as my branch. Also, the 
documentation says that the  parameter defaults to HEAD, so passing 
'HEAD' explicitly should result in the same behavior as not passing it:
 Working branch; defaults to HEAD.

Pierre-Luc Loyer
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