Re: RFC: a plugin architecture for git extensions?

From: Jeff King <peff@peff.net>
Date: May 9, 2011, 08:12 UTC
Message-ID: <20110509081219.GB6205@sigill.intra.peff.net>
In-Reply-To: <BANLkTi=tfxPN=WLmfn=d+jrHV3U-Rp8T=A@mail.gmail.com>

On Mon, May 09, 2011 at 05:49:27PM +1000, Jon Seymour wrote:

Show 20 quoted lines

> Yep, that was part of the motivation for the suggestion - something
> that works consistently, assuming only a working git installation.
> 
> Per one of my other notes, my initial inclination is to provide a
> patch that implements support for
> 
>      git --system-extensions-dir
> 
> which would:
>    - provide the caller with location that extensions could be
> installed in (assuming the caller can acquire write privileges)
>    - provide a guarantee that $(git --system-extensions-dir)/bin will
> be on the path set up by the git wrapper and $(git
> --system-extensions-dir)/man will be in the MANPATH searched by git
> help
> 
> Extensions could then use this information, together with git
> --html-path to install themselves into these places using whatever
> mechanism seems appropriate (either a POSIX shell script or a
> make/install script).

But is the system extension dir always the right place to do so? If I'm not root, then that probably won't be writable (or even if I am, I may want to install the extension only for the root user).

If your proposal is for the user to decide on one of:

  unzip -d "$(git --system-extension-dir)" git-foo.zip

or

  unzip -d "$HOME/.gitplugins" git-foo.zip

then they can make that decision. But if you're proposing that the extension-writer distribute a script, then it's more complicated. They would probably need to provide a "--user" versus "--system" option.

It would also be tempting to write something like:

  install_dir() {
    if test "`id -u`" = "0"; then
      git --system-extension-dir
    else
      echo $HOME/.gitplugins
    fi
  }

but that is:

  1. Not portable.

  2. Does not allow for user-only installation by root.

But all of this is a packaging best-practices issue, not an issue of what git needs to do to support it (you _could_ address the portability issue by having "git --preferred-extension-path" that did the appropriate platform-specific UID check, but that still doesn't address the second point).

-Peff