fix "bundle --stdin" segfault
fix "bundle --stdin" segfault

When passed an empty list, objects_array_remove_duplicates() corrupts it
by changing the number of entries from 0 to 1.

The problem lies in the condition of its main loop:

	for (ref = 0; ref < array->nr - 1; ref++) {

The loop body manipulates the supplied object array.  In the case of an
empty array, it should not be doing anything at all.  But array->nr is an
unsigned quantity, so the code enters the loop, in particular increasing
array->nr.  Fix this by comparing (ref + 1 < array->nr) instead.

This bug can be triggered by git bundle --stdin:

	$ echo HEAD | git bundle create some.bundle --stdin’
	Segmentation fault (core dumped)

The list of commits to bundle appears to be empty because of another bug:
by the time the revision-walking machinery gets to look at it, standard
input has already been consumed by rev-list, so this function gets an
empty list of revisions.

After this patch, git bundle --stdin still does not work; it just doesn’t
segfault any more.

Reported-by: Joey Hess <56a580ad3befc663da709977ba17447ffa133c85@kitenet.net>
Signed-off-by: Jonathan Nieder <b57189c5f2fd5b3daf3350a77fde90def1080fa5@gmail.com>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git