Re: git merge error question: The following untracked working tree files would be overwritten by merge

[Junio C Hamano <gitster@pobox.com>]

Carsten Fuchs <carsten.fuchs@cafu.de> writes:

> Hi all,
>
> in my repo, I'm doing this:
>
>> $ git status
>> # On branch master
>> # Your branch is behind 'origin/master' by 2 commits, and can be fast-forwarded.
>> #
>> # Untracked files:
>> #   (use "git add <file>..." to include in what will be committed)
>> #
>> #       obsolete/
>> nothing added to commit but untracked files present (use "git add" to track)
>>
>> $ git merge origin/master --ff-only
>> Updating f419d57..2da6052
>> error: The following untracked working tree files would be overwritten by merge:
>>         obsolete/e107/Readme.txt
>>         obsolete/e107/article.php
>>         obsolete/e107/backend.php
>>         [...]
> ...
> Compare with what Subversion did in an analogous case: When I ran "svn
> update" and the update brought new files for which there already was
> an untracked copy in the working directory, Subversion:
>     - started to consider the file as tracked,
>     - but left the file in the working-copy alone.
>
> As a result, a subsequent "svn status" might
>     a) no longer show the file at all, if the foreign copy in the
> working directory happened to be the same as the one brought by the
> "svn update", or
>     b) flag the file as modified, if different from the one that "svn
> update" would have created in its place.

Interesting.  So before running "status", the merge is recorded (in this
particular case you are doing ff-only so there is nothing new to
record, but if the rest of the tree merges cleanly, the new tree
that contains "obsolete" from the other branch you just merged will
be the contents you record in the merge commit), and working tree is
immediately dirty?  It makes sense, even though I haven't tried to
think things through to see if there are tricky corner cases.

> So my real question is, why does Git not do something analogous?

The answer to that question is "because nobody thought that doing so
would help users very much and bothered to implement it"; it is not
"people thought about doing so and found reasons why that would not
help users".