From: Thomas Rast <trast@inf•ethz.ch>
To: Jim Greenleaf <james.a.greenleaf@gmail•com>
Cc: <git@vger•kernel.org>, Petr Baudis <pasky@ucw•cz>,
Junio C Hamano <gitster@pobox•com>
Subject: Re: git stash deletes/drops changes of
Date: Fri, 24 May 2013 00:10:51 +0200 [thread overview]
Message-ID: <87sj1d5ous.fsf@linux-k42r.v.cablecom.net> (raw)
In-Reply-To: <loom.20130523T185301-635@post.gmane.org> (Jim Greenleaf's message of "Thu, 23 May 2013 16:57:23 +0000 (UTC)")
Jim Greenleaf <james.a.greenleaf@gmail•com> writes:
> Adeodato Simó <dato <at> net.com.org.es> writes:
>
>> I was unpleasantly surprised to discover yesterday that doing `git
>> stash` on a repository where I had previously run `git update-index
>> --assume-unchanged FOO` completely lost all changes I had in file FOO.
>
> I just ran into this today.
>
> Was a decision about this behavior reached in the intervening time?
When you mark a file assume-unchanged, git internally sets a flag that
this file should not be considered when doing cache refreshes -- the
file is always assumed to be up-to-date.
So while I haven't actually looked into all of the code, I imagine it
goes something like this:
* git-stash uses git update-index --all on all modified files. But it
doesn't show up as modified, because you promised it isn't.
* Later it calls git reset --hard, which blows away the existing state.
This would seem to ignore the assume-unchanged flag in this case, as
otherwise it wouldn't overwrite it.
Whether the last behavior is a bug is in the eye of the beholder. In
your case you apparently lost work. However, 'git reset --hard' in
itself should discard all uncommitted work without asking any further
questions (because it's --hard). So the bug is then in the sequence
ask about uncommitted work
save it elsewhere
git reset --hard
assuming that this actually makes sure nothing gets lost. But the only
thing that was lost was *files that you promised would not be changed*.
What's really unfortunate is that we caused this in the first place by
Pasky's 6259ac6 (Documentation: How to ignore local changes in tracked
files, 2008-07-18). It recommends exactly the --assume-unchanged
strategy to ignore changes to tracked files.
And it's hard to disagree with its commit message:
This is currently probably one of the top FAQs at #git and the
--assume-unchanged switch is not widely known
Except that now the corresponding FAQ is that we have to actively
dissuade people from using --assume-unchanged precisely because it keeps
biting people.
So maybe it would be time to first make up our minds as to what
--assume-unchanged should actually mean:
* Ignore changes to a tracked file, but treat them as valuable. In
this case we'd have to make sure that failures like git-stash's are
handled properly.
* Ignore changes to a tracked file, as in "who cares if it was changed".
* A very specific optimization for users who know what they are doing.
--
Thomas Rast
trast@{inf,student}.ethz.ch
next prev parent reply other threads:[~2013-05-23 22:11 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-04 16:24 git stash deletes/drops changes of "assume-unchanged" files Adeodato Simó
2013-05-23 16:57 ` git stash deletes/drops changes of Jim Greenleaf
2013-05-23 22:10 ` Thomas Rast [this message]
2013-05-23 22:49 ` Junio C Hamano
2013-05-23 22:56 ` Thomas Rast
2013-05-23 23:20 ` Junio C Hamano
2013-05-24 15:25 ` Phil Hord
2013-05-24 15:34 ` Jim Greenleaf
2013-05-24 15:38 ` John Keeping
2013-05-24 15:42 ` Jim Greenleaf
2013-05-24 16:01 ` John Keeping
2013-05-23 23:57 ` Petr Baudis
2013-05-24 8:22 ` John Keeping
2013-05-24 9:40 ` Petr Baudis
2013-05-24 10:06 ` John Keeping
2013-05-24 10:14 ` Petr Baudis
2013-05-24 10:40 ` John Keeping
2013-05-24 11:03 ` Petr Baudis
2013-05-24 12:42 ` John Keeping
2013-05-24 14:26 ` Stephen Bash
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