[PATCH 6/6] run_external_diff: refactor cmdline setup logic

[Jeff King <peff@peff.net>]

The current logic makes it hard to see what gets put onto
the command line in which cases. Pulling out a helper
function lets us see that we have two sets of file data, and
the second set either uses the original name, or the "other"
renamed/copy name.

Signed-off-by: Jeff King <peff@peff.net>
---
The last patch and this one are getting a little bit into code churn,
perhaps. I think the prior one is hands-down more readable. This one, I
am on the fence on whether it is a true improvement or simply "this is
how _I_ would have written it". I won't be offended if we drop it.

 diff.c | 26 +++++++++++++++-----------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/diff.c b/diff.c
index 173b657..4b8bfc6 100644
--- a/diff.c
+++ b/diff.c
@@ -2888,6 +2888,16 @@ static struct diff_tempfile *prepare_temp_file(const char *name,
 	return temp;
 }
 
+static void add_external_diff_name(struct argv_array *argv,
+				   const char *name,
+				   struct diff_filespec *df)
+{
+	struct diff_tempfile *temp = prepare_temp_file(name, df);
+	argv_array_push(argv, temp->name);
+	argv_array_push(argv, temp->hex);
+	argv_array_push(argv, temp->mode);
+}
+
 /* An external diff command takes:
  *
  * diff-cmd name infile1 infile1-sha1 infile1-mode \
@@ -2911,17 +2921,11 @@ static void run_external_diff(const char *pgm,
 	argv_array_push(&argv, name);
 
 	if (one && two) {
-		struct diff_tempfile *temp_one, *temp_two;
-		const char *othername = (other ? other : name);
-		temp_one = prepare_temp_file(name, one);
-		temp_two = prepare_temp_file(othername, two);
-		argv_array_push(&argv, temp_one->name);
-		argv_array_push(&argv, temp_one->hex);
-		argv_array_push(&argv, temp_one->mode);
-		argv_array_push(&argv, temp_two->name);
-		argv_array_push(&argv, temp_two->hex);
-		argv_array_push(&argv, temp_two->mode);
-		if (other) {
+		add_external_diff_name(&argv, name, one);
+		if (!other)
+			add_external_diff_name(&argv, name, two);
+		else {
+			add_external_diff_name(&argv, other, two);
 			argv_array_push(&argv, other);
 			argv_array_push(&argv, xfrm_msg);
 		}
-- 
1.9.1.656.ge8a0637