Re: [PATCH 1/2] merge-recursive: prepare merge_recursive() to be called from builtins

[Junio C Hamano <gitster@pobox.com>]

Stephan Beyer <s-beyer@gmx.net> writes:

> Hmm, I have the long-run vision that we have a nice libgit some day,
> with merge_recursive() being part of it.  And I'm a little unsure if
> libified functions should rely on environment variables.

I think the environment variable is the least of your worries.  

I do not think anybody has vetted if it is safe to call merge_recursive()
more than once in a single run of a process.  Things to watch out for are
the use of static variables (e.g. current_{file,directory}_set that are
used for its (semi-broken) D/F conflict detection), its liberal use of
die(), leaking of "virtual commit", to name a few.  They are all perfectly
fine programming constructs when we assume this is a one-shot "run and
clean up with exit" program, but whoever wants to libify it needs to
arrange them to be cleaned up inside the "library" without making the code
too ugly nor one-shot use too expensive.

But such a clean-up may not be too bad as I initially feared, I suppose.
After a cursory look in builtin-merge-recursive.c, at least it does not
seem to mark objects with random object flags, expecting that nobody else
will look at them after it exits --- which would have been very expensive
to clean up after the fact.