[PATCH] run_diff_files(): clarify computation of sha1 validity

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

Remove the need to have duplicated "if there is a change then feed
null_sha1 and otherwise sha1 from the cache entry" for the "new"
side of the diff by introducing two temporary variables to point
at the object name of the old and the new side of the blobs.

This does not intend to change the meaning of the code in any way;
just makes the result a bit easier to read.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---

 * A random thing I noticed while reading existing code...

 diff-lib.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/diff-lib.c b/diff-lib.c
index 875aff8..a85c497 100644
--- a/diff-lib.c
+++ b/diff-lib.c
@@ -101,6 +101,7 @@ int run_diff_files(struct rev_info *revs, unsigned int option)
 		struct cache_entry *ce = active_cache[i];
 		int changed;
 		unsigned dirty_submodule = 0;
+		const unsigned char *old_sha1, *new_sha1;
 
 		if (diff_can_quit_early(&revs->diffopt))
 			break;
@@ -224,9 +225,12 @@ int run_diff_files(struct rev_info *revs, unsigned int option)
 				continue;
 		}
 		oldmode = ce->ce_mode;
+		old_sha1 = ce->sha1;
+		new_sha1 = changed ? null_sha1 : ce->sha1;
 		diff_change(&revs->diffopt, oldmode, newmode,
-			    ce->sha1, (changed ? null_sha1 : ce->sha1),
-			    !is_null_sha1(ce->sha1), (changed ? 0 : !is_null_sha1(ce->sha1)),
+			    old_sha1, new_sha1,
+			    !is_null_sha1(old_sha1),
+			    !is_null_sha1(new_sha1),
 			    ce->name, 0, dirty_submodule);
 
 	}
-- 
2.3.0-rc2-170-g6029c0c