Re: git pull --rebase=preserve is always rebasing something, even on up-to-date branch

From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Nov 16, 2018, 12:49 UTC
Message-ID: <nycvar.QRO.7.76.6.1811161345580.41@tvgsbejvaqbjf.bet>
In-Reply-To: <CADhDkKwHp0dR7PPLV6UZDmSO9ERW7Opym3FSD64XXTg-QK65bw@mail.gmail.com>

Hi Mikhail,

On Mon, 17 Sep 2018, Mikhail Matrosov wrote:

Show 28 quoted lines

> Please try the following:
> 
> mmatrosov@Mikhail-PC:~/test$ git init --bare server
> Initialized empty Git repository in /home/mmatrosov/test/server/
> mmatrosov@Mikhail-PC:~/test$ git clone server local
> Cloning into 'local'...
> warning: You appear to have cloned an empty repository.
> done.
> mmatrosov@Mikhail-PC:~/test$ cd local
> mmatrosov@Mikhail-PC:~/test/local$ echo a > a && git add . && git commit -m A
> [master (root-commit) a34c21f] A
>  1 file changed, 1 insertion(+)
>  create mode 100644 a
> mmatrosov@Mikhail-PC:~/test/local$ git push
> Counting objects: 3, done.
> Writing objects: 100% (3/3), 205 bytes | 0 bytes/s, done.
> Total 3 (delta 0), reused 0 (delta 0)
> To /home/mmatrosov/test/server
>  * [new branch]      master -> master
> mmatrosov@Mikhail-PC:~/test/local$ git pull
> Already up-to-date.
> mmatrosov@Mikhail-PC:~/test/local$ git pull --rebase=preserve
> Rebasing (1/1)
> Successfully rebased and updated refs/heads/master.
> 
> As you can see, running bare "git pull" just tells me everything is up
> to date. However, running "git pull --rebase=preserve" triggers
> rebasing of something.

This is most likely a `noop` command.

> It wont be a problem if it didn't take significant time (especially on
> Windows). Why this rebase happens? It is completely redundant and slows
> down the pull operation. Looks like a bug to me.

It is an implementation detail, and if you want to work on fixing it, please let me know about your availability and C skill level.

> 
> Note that it is important to me, because I want to set "git config
> --global pull.rebase preserve".

Please note that `preserve` is on its way to deprecation, superseded by `pull.rebase = merges`. Which may, or may not, share the performance penalty you reported. Probably not, though.

Ciao, Johannes

Show 10 quoted lines

> But because of this issue, pulling on an up-to-date repository takes a
> lot of time. Which is very frustrating.
> 
> Tested with:
> * git version 2.19.0.windows.1 in Windows 10 Version 1803
> * git version 2.7.4 in Ubuntu 16.04.3 LTS (inside WSL)
> 
> -----
> Best regards, Mikhail Matrosov
>