[RFC/PATCH 0/6] Graceful handling of missing remote helpers

From: Johan Herland <johan@herland.net>
Date: Aug 11, 2009, 10:10 UTC
Message-ID: <1249985426-13726-1-git-send-email-johan@herland.net>
In-Reply-To: <alpine.LNX.2.00.0908101205120.27553@iabervon.org>

On Mon, 10 Aug 2009, Daniel Barkalow wrote:

Show 15 quoted lines

> > > In order to support this, there just needs to be a call to check whether
> > > "remote-<something>" is an available git command (without running it or
> > > giving an error), and the helper code should be used if it is. This is
> > > actually required so that people with workstations whose domain is
> > > .kernel.org and who have cloned "master:/home/linus/something.git" don't
> > > start getting "remote-master isn't a git command" errors (that is,
> > > misinterpreting ssh-format location hostnames as helper names. Johan,
> > > perhaps you could write that for your CVS helper?
> >
> > Sorry, not following you here. Write exactly what?
> >
> > - The code in the transport layer for checking if "remote-<something>"
> >   is an available git command?
>
> That's what I was thinking.

Ok, I've spent way too much time on this, so if this doesn't cut it, I leave it up to someone else to pick up the pieces.

The following patch series implements what I understand to be the current consensus (or at least a good compromise) in this thread:

- There are two ways to indicate that a remote helper should be used:
  1. remote.foo.vcs = <something>
  2. remote.foo.url starts with "<something>:"
  If both are present, remote.foo.vcs is preferred.

- Teach transport_helper_init() to check if "remote-<something>" is an
  available git command. If so, use it. If not, gracefully abort the
  transport-helper setup, and fall back to the "native" transport code.

- Skip the transport-helper code is the remote is obviously "native" (i.e.
  URL starts with "git:"/"file:"/"ssh:"/"rsync:")

AFAICS this should make Daniel happy because his P4 setup will still work, and
it should also make Dscho happy, since he can tell people to
  "git clone cvs::pserver:anonymous@cool.haxx.se:/cvsroot/curl#curl"
(of course, this depends on the CVS helper supporting remote.foo.url, which it
will, in a future iteration)

The non-trivial part of the series is in patch #5.

Implementing the rsync handling as another remote helper program is left as an exercise for the reader...

Have fun! :)

...Johan

Johan Herland (6):
  Minor unrelated fixes
  transport_get(): Don't SEGFAULT on missing url
  Move setup of curl remote helper from transport.c to transport-helper.c
  Add is_git_command_or_alias() for checking availability of a given git command
  Let transport_helper_init() decide if a remote helper program can be used
  Add testcase to verify handling of missing remote helper programs

 help.c                           |   23 ++++++++++++-
 help.h                           |    2 +
 t/t5590-remote-helper-missing.sh |   56 +++++++++++++++++++++++++++++++
 transport-helper.c               |   67 +++++++++++++++++++++++++++++++++++--
 transport.c                      |   56 ++++++-------------------------
 5 files changed, 154 insertions(+), 50 deletions(-)
 create mode 100755 t/t5590-remote-helper-missing.sh