[PATCH v2] diff: Fix modified lines stats with --stat and --numstat

[Thomas Guyot-Sionnest <tguyot@gmail.com>]

In builtin_diffstat(), when both files are coming from "stdin" (which
could be better described as the file's content being written directly
into the file object), oideq() compares two null hashes and ignores the
actual differences for the statistics.

This patch checks if is_stdin flag is set on both sides and compare
contents directly.

Signed-off-by: Thomas Guyot-Sionnest <tguyot@gmail.com>
---
Range-diff:
1:  479c2835fc ! 1:  1f25713d44 diff: Fix modified lines stats with --stat and --numstat
    @@ -20,8 +20,12 @@
      	}
      
     -	same_contents = oideq(&one->oid, &two->oid);
    ++	/* What is_stdin really means is that the file's content is only
    ++	 * in the filespec's buffer and its oid is zero. We can't compare
    ++	 * oid's if both are null and we can just diff the buffers */
     +	if (one->is_stdin && two->is_stdin)
    -+		same_contents = !strcmp(one->data, two->data);
    ++		same_contents = (one->size == two->size ?
    ++			!memcmp(one->data, two->data, one->size) : 0);
     +	else
     +		same_contents = oideq(&one->oid, &two->oid);
      

 diff.c                | 9 ++++++++-
 t/t3206-range-diff.sh | 8 ++++----
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/diff.c b/diff.c
index ee8e8189e9..2e47bf824e 100644
--- a/diff.c
+++ b/diff.c
@@ -3681,7 +3681,14 @@ static void builtin_diffstat(const char *name_a, const char *name_b,
 		return;
 	}
 
-	same_contents = oideq(&one->oid, &two->oid);
+	/* What is_stdin really means is that the file's content is only
+	 * in the filespec's buffer and its oid is zero. We can't compare
+	 * oid's if both are null and we can just diff the buffers */
+	if (one->is_stdin && two->is_stdin)
+		same_contents = (one->size == two->size ?
+			!memcmp(one->data, two->data, one->size) : 0);
+	else
+		same_contents = oideq(&one->oid, &two->oid);
 
 	if (diff_filespec_is_binary(o->repo, one) ||
 	    diff_filespec_is_binary(o->repo, two)) {
diff --git a/t/t3206-range-diff.sh b/t/t3206-range-diff.sh
index e024cff65c..4715e75b68 100755
--- a/t/t3206-range-diff.sh
+++ b/t/t3206-range-diff.sh
@@ -258,11 +258,11 @@ test_expect_success 'changed commit with --stat diff option' '
 	     a => b | 0
 	     1 file changed, 0 insertions(+), 0 deletions(-)
 	3:  $(test_oid t3) ! 3:  $(test_oid c3) s/11/B/
-	     a => b | 0
-	     1 file changed, 0 insertions(+), 0 deletions(-)
+	     a => b | 2 +-
+	     1 file changed, 1 insertion(+), 1 deletion(-)
 	4:  $(test_oid t4) ! 4:  $(test_oid c4) s/12/B/
-	     a => b | 0
-	     1 file changed, 0 insertions(+), 0 deletions(-)
+	     a => b | 2 +-
+	     1 file changed, 1 insertion(+), 1 deletion(-)
 	EOF
 	test_cmp expect actual
 '
-- 
2.20.1