[PATCH (take 2)] Use diff-tree -p instead of "git diff" in git-export.

Now diff-tree can produce patch itself, there is no reason to
depend on Cogito to show diff in the git-export output anymore.

Signed-off-by: Junio C Hamano <redacted>
---

This is a reworked patch---we just made -p to imply recursive so
we can just say diff-tree -p, not diff-tree -p -r like I said in
the previous patch.

git-export.c |    2 +-
1 files changed, 1 insertion(+), 1 deletion(-)

--- k/git-export.c
+++ l/git-export.c

@@ -18,7 +18,7 @@ void show_commit(struct commit *commit)
 		char *against = sha1_to_hex(commit->parents->item->object.sha1);
 		printf("\n\n======== diff against %s ========\n", against);
 		fflush(NULL);
-		sprintf(cmdline, "git diff -r %s:%s", against, hex);
+		sprintf(cmdline, "diff-tree -p %s %s", against, hex);
 		system(cmdline);
 	}
 	printf("======== end ========\n\n");