Re: [PATCH] Make stashing nothing exit 1

From: Maksim Odnoletkov <odnoletkov@mail.ru>
Date: May 22, 2019, 23:57 UTC
Message-ID: <20190522235705.68452-1-odnoletkov@mail.ru>
In-Reply-To: <xmqqh8bsphny.fsf@gitster-ct.c.googlers.com>

Junio C Hamano <gitster@pobox.com> writes:

Show 14 quoted lines

> Keith Smiley <keithbsmiley@gmail.com> writes:
> 
> > In the case there are no files to stash, but the user asked to stash, we
> > should exit 1 since the stashing failed.
> > ---
> 
> Sorry, but I fail to see why this is a good change.  Did you have
> some script that wanted the exit code from "git stash" to indicate
> if it had anything to stash and change the behaviour based on it?
> 
> Is it a big enough hassle to figure out if the "stash" command did
> something yourself that justifies forcing existing scripts that rely
> on "no-op is merely a normal exit" behaviour other people have
> written in the past several years?

The problem with current behaviour is it makes it hard to use stash in scripts. A natural stash use case is: wrap some operation requiring a clean working tree with a stash push-pop pair. But that doesn't work properly when working tree is already clean - push silently does nothing and following pop becomes unbalanced. You have to keep that in mind and work around with something like:

if ! git diff-index --exit-code --quiet HEAD
then
	git stash push
	trap 'git stash pop' EXIT
fi

With this change this can be simplified to:

git stash push && trap 'git stash pop' EXIT

I don't mind keeping this new behaviour behind an option for compatibility. Or alternatively resolve this use case by supporting --allow-empty in stash-push. But my feeling is it is natural for 'git stash push' to report error for no-op case because the command is explicitly about creating new stash entries. A close analogy is 'git commit' which errors on no-op. Contrary all commands treating no-op as a success I'm aware of are not about creating new objects but about querying or syncing.