Re: [PATCH 4/6] config: return configset value for current_config_ functions

[Jeff King <peff@peff.net>]

On Thu, May 26, 2016 at 10:36:44AM -0700, Junio C Hamano wrote:

> Jeff King <peff@peff.net> writes:
> 
> > The problem is running test-config inside of a git alias. The
> > bin-wrappers will set the exec-path to the root-level of git's build
> > directory, which the git binary will then stick at the front of the
> > $PATH.
> 
> I was wondering why exec-path does not point at bin-wrappers in the
> first place.
> 
> A wrapper script needs to know where the real thing lives in order
> to "exec" (or "exec gdb") anyway, and it hardcodes the path to it.
> It happens to use GIT_EXEC_PATH to shorten the hardcoded path it
> uses when it does "exec", but it does not have to.
> 
> Wouldn't we want to see "git" use any of these wrapped ones when it
> invokes a non-builtin subcommand when it does so normally, honoring
> GIT_EXEC_PATH?  Pointing GIT_EXEC_PATH at the top-level means that
> wrappers are bypassed for such an invocation (if what is run happens
> to have executable at the top-level), and possibly a totally wrong
> thing is run (when we start generating the binaries in different
> directories, which is what we are seeing here).

I think the issue is that bin-wrappers serves two purposes. One is for
testing, but the other is for people who run git directly without
installing. For us to set GIT_EXEC_PATH to bin-wrappers, it would have
to have all of the git-* external programs, which would then put them
all in the $PATH of people doing the no-install thing.

That's certainly not insurmountable. Either we can tell them to live
with it, or we can break out a separate wrapper directory that serves as
a pseudo-exec-path.

> > So the simplest solution really is: don't do that. The only debate
> > in my mind is whether this is rare enough that it won't bite
> > somebody again in the future, or if we should look into a solution
> > that makes this Just Work.
> 
> I think it was you who alluded to revamping the test framework along
> the lines of preparing a "test installation" (aka "make install"
> with DESTDIR set to somewhere) and making bin-wrappers to point into
> that installation (or if we are testing an installed Git that may be
> different from what we have source for, that final installed
> location).  An installed version of Git will not have test-* helpers
> so they need to come from a freshly built source tree, not from
> "test installation" or "installed Git".  There may be other details
> that need to be worked out, but as a longer term direction that may
> not be a bad idea.

I think you can make it even simpler by not really doing a "make
install", but just linking or bin-wrappering a fake exec-path. It would
be great if we could truly just "make install" into a fake area and test
that (dropping bin-wrappers entirely), but git cares too much about some
hard-coded paths, I think. We'd have to first have a truly relocatable
binary.

-Peff