Merge branch 'sg/diff-multiple-identical-renames' into maint

"git diff -M" used to work better when two originally identical
files A and B got renamed to X/A and X/B by pairing A to X/A and B
to X/B, but this was broken in the 2.0 timeframe.

* sg/diff-multiple-identical-renames:
  diffcore: fix iteration order of identical files during rename detection

Author: gitster

diffcore-rename.c

@@ -340,9 +340,11 @@ static int find_exact_renames(struct diff_options *options)
 	int i, renames = 0;
 	struct hashmap file_table;
 
-	/* Add all sources to the hash table */
+	/* Add all sources to the hash table in reverse order, because
+	 * later on they will be retrieved in LIFO order.
+	 */
 	hashmap_init(&file_table, NULL, rename_src_nr);
-	for (i = 0; i < rename_src_nr; i++)
+	for (i = rename_src_nr-1; i >= 0; i--)
 		insert_file_table(&file_table, i, rename_src[i].p->one);
 
 	/* Walk the destinations and find best source match */

t/t4001-diff-rename.sh

@@ -77,6 +77,17 @@ test_expect_success 'favour same basenames even with minor differences' '
 	git show HEAD:path1 | sed "s/15/16/" > subdir/path1 &&
 	git status | test_i18ngrep "renamed: .*path1 -> subdir/path1"'
 
+test_expect_success 'two files with same basename and same content' '
+	git reset --hard &&
+	mkdir -p dir/A dir/B &&
+	cp path1 dir/A/file &&
+	cp path1 dir/B/file &&
+	git add dir &&
+	git commit -m 2 &&
+	git mv dir other-dir &&
+	git status | test_i18ngrep "renamed: .*dir/A/file -> other-dir/A/file"
+'
+
 test_expect_success 'setup for many rename source candidates' '
 	git reset --hard &&
 	for i in 0 1 2 3 4 5 6 7 8 9;