Re: [PATCH] run-command.c: Accept EACCES as command not found

From: Frans Klaver <fransklaver@gmail.com>
Date: Nov 22, 2011, 09:31 UTC
Message-ID: <CAH6sp9MxbDhQ3RiA6jO1fswAZX3R6C2fv0gzJdpGp432ovWsjQ@mail.gmail.com>
In-Reply-To: <7v62idf2vy.fsf@alter.siamese.dyndns.org>

On Tue, Nov 22, 2011 at 12:54 AM, Junio C Hamano <gitster@pobox.com> wrote:

> Imagine you did not have alias.aliasedinit in ~/.gitconfig but had a
> script called $(pwd)/searchpath/git-aliasedinit which we would fail to
> execute. What message would we get in that case? Currently I think we get
> permission denied.

Correct.

> Would we get the same with your patch, or something that does not hint
> at all that there is a permission problem?

Nope. That would be just as confusing and inarguably incorrect at that -- bash differentiates between commands that exist, but cannot be executed due to permissions (access denied) and paths that cannot be read (they are ignored in the search).

Show 6 quoted lines

> See also the "tangent" part of
>
>    http://thread.gmane.org/gmane.comp.version-control.git/171755
>
> and the discussion that follows it. I do not think we reached any
> conclusion nor a patch.

There's no black-on-white conclusion there. I get the impression that no one really has an idea of what they want when encountering EACCES. Git has to do what's reasonable to provide the user with information. Currently I think it does too little. Jonathan N. gave the option of optionally using libexplain[1]. It's pretty verbose and accurate:

fatal: cannot exec 'git-frotz': execvp(pathname = "git-frotz", argv = ["git-frotz"]) failed, Permission denied (13, EACCES) because the process does not have search permission to the pathname "/home/frans/devsw/searchpath" directory, the process effective UID 1000 "frans" matches the directory owner UID 1000 "frans" and the owner permission mode is "r--", and the process is not privileged (does not have the DAC_READ_SEARCH capability): Success

I wouldn't be in favor of adding the dependency just to enable users to track down PATH issues though. Also, I think "Cannot access /home/frans/devsw/searchpath" would just as well do the trick.

For Jonathan's example[2] libexplain doesn't have a clear answer either: fatal: cannot exec 'git-frotz': execvp(pathname = "git-frotz", argv = ["git-frotz"]) failed, Permission denied (13, EACCES): Permission denied

If git is going to do some diagnostics on why the execvp returned EACCES, it can still give a few hints. Most of the more likely options are then ruled out.

Frans

[1] http://article.gmane.org/gmane.comp.version-control.git/171860 [2] http://article.gmane.org/gmane.comp.version-control.git/171848