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Re: fast forward merge overwriting my code

From
brian m. carlson <sandals@crustytoothpaste.net>
Date
May 23, 2021, 23:58 UTC
Message-ID
<YKrsC9CaG/KDvDBi@camp.crustytoothpaste.net>
In-Reply-To
<4c1c3dbc-7a89-02db-3883-b7eea644cd83@kdbg.org>
On 2021-05-23 at 09:48:55, Johannes Sixt wrote:
Show 33 quoted lines
> [resending, as I forgot to include git@vger]
> 
> Am 22.05.21 um 17:48 schrieb Andre Ulrich:
> > Let's say I have a .txt file on my master branch. I used
> > 
> > git add .
> > 
> > and
> > 
> > git commit -m "blabla"
> > 
> > so everything is staged and in the history. Now I check out a new branch
> > 
> > git checkout -b testing
> > 
> > and edit the .txt file. I add some new lines at the end, but I also
> > change some of the already existing lines. Then again I add and commit
> > everything. Then I use
> > 
> > git checkout master
> > 
> > and
> > 
> > git merge testing
> > 
> > I would expect git to tell me "hey, wait, you have changed some of the
> > first lines in the .txt file. When you merge, your code on master will
> > be altered". But git just merges everything in.
> > Just imagine this was working code, and changing some of the first lines
> > breaks everything in the following lines.
> > I think I have found out what is the problem: git considers this a fast
> > forward merge (since there were no commits on master between the
> > creation and the merging of the test branch).

Yes. However, if Git did an actual merge, the result would be the same. In a three-way merge, if one side changes, and the other does not, the change is adopted. A fast-forward merge just avoids the merge commit.

Show 13 quoted lines
> > But this is annoying. I want to be able to choose, what changes I want
> > to keep, when I do the merge (just as in case of a 3way merge, when you
> > can call a graphical merge tool to decide what lines to keep).
> 
> But in a 3-way merge, you only get to choose which changes you take if
> there is a conflict. If, in your example, you had committed a change to
> a different file on master before the merge, you would get a
> non-fast-forward (3-way) merge, and still no opportunity to choose which
> changes you take because there would be no conflict.
> 
> And why do you think we need a general warning "when you merge, your
> code on master will be altered"? Why would I want to make a merge into
> master if not to change the code on master?

I suspect Andre has a goal here or a specific use case that we're not understanding. If we got some more explanation about what's going on, we could probably offer a more useful response addressing that specific use case or goal. It might not be a use case we support, but at least we could address it directly.

-- 
brian m. carlson (he/him or they/them)
Houston, Texas, US
Previous: Johannes SixtNext: Andre Ulrich
Message 6 of 23 in “fast forward merge overwriting my code”
  1. Andre UlrichMay 22, 2021
  2. Philip OakleyMay 22, 2021
  3. Junio C HamanoMay 23, 2021
  4. Philip OakleyMay 24, 2021
  5. Johannes SixtMay 23, 2021
  6. brian m. carlsonMay 23, 2021
  7. Andre UlrichMay 24, 2021
  8. Bagas SanjayaMay 24, 2021
  9. Philip OakleyMay 24, 2021
  10. Andre UlrichMay 24, 2021
  11. Philip OakleyMay 24, 2021
  12. Philip OakleyMay 25, 2021
  13. David AguilarMay 30, 2021
  14. Philip OakleyMay 30, 2021
  15. Igor DjordjevicMay 24, 2021
  16. Felipe ContrerasMay 26, 2021
  17. Philip OakleyMay 26, 2021
  18. Felipe ContrerasMay 26, 2021
  19. Philip OakleyMay 26, 2021
  20. Felipe ContrerasMay 26, 2021
  21. Philip OakleyMay 27, 2021
  22. Felipe ContrerasMay 27, 2021
  23. Philip OakleyMay 27, 2021

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