t7606: Avoid using head as a file name

A file named 'head' gets confused with the HEAD ref on
case-insensitive file systems.  Replace '>head' with '>head.new' to
match the '>head.old' files they are compared to.

Signed-off-by: Brian Gernhardt <brian@gernhardtsoftware.com>
Acked-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: Benabik

t/t7606-merge-custom.sh

@@ -46,7 +46,7 @@ test_expect_success 'merge c2 with a custom strategy' '
 	git rev-parse c2^{tree} >tree.expected &&
 	git merge -s theirs c2 &&
 
-	git rev-parse HEAD >head &&
+	git rev-parse HEAD >head.new &&
 	git rev-parse HEAD^1 >first-parent &&
 	git rev-parse HEAD^2 >second-parent &&
 	git rev-parse HEAD^{tree} >tree &&
@@ -55,7 +55,7 @@ test_expect_success 'merge c2 with a custom strategy' '
 	git diff --exit-code c2 HEAD &&
 	git diff --exit-code c2 &&
 
-	! test_cmp head.old head &&
+	! test_cmp head.old head.new &&
 	test_cmp head.old first-parent &&
 	test_cmp second-parent.expected second-parent &&
 	test_cmp tree.expected tree &&
@@ -72,7 +72,7 @@ test_expect_success 'trivial merge with custom strategy' '
 	git rev-parse c3^{tree} >tree.expected &&
 	git merge -s theirs c3 &&
 
-	git rev-parse HEAD >head &&
+	git rev-parse HEAD >head.new &&
 	git rev-parse HEAD^1 >first-parent &&
 	git rev-parse HEAD^2 >second-parent &&
 	git rev-parse HEAD^{tree} >tree &&
@@ -81,7 +81,7 @@ test_expect_success 'trivial merge with custom strategy' '
 	git diff --exit-code c3 HEAD &&
 	git diff --exit-code c3 &&
 
-	! test_cmp head.old head &&
+	! test_cmp head.old head.new &&
 	test_cmp head.old first-parent &&
 	test_cmp second-parent.expected second-parent &&
 	test_cmp tree.expected tree &&