[PATCH] mergetools/p4merge: Honor $TMPDIR for the /dev/null placeholder

[David Aguilar <davvid@gmail.com>]

Use mktemp to create the /dev/null placeholder for p4merge.
This keeps it out of the current directory.

Reported-by: Jeremy Morton <admin@game-point.net>
Signed-off-by: David Aguilar <davvid@gmail.com>
---
I consider this a final finishing touch on a new 1.8.1 feature,
so hopefully we can get this in before 1.8.1.

 mergetools/p4merge | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/mergetools/p4merge b/mergetools/p4merge
index 295361a..090fa9b 100644
--- a/mergetools/p4merge
+++ b/mergetools/p4merge
@@ -4,13 +4,13 @@ diff_cmd () {
 	rm_remote=
 	if test "/dev/null" = "$LOCAL"
 	then
-		LOCAL="./p4merge-dev-null.LOCAL.$$"
+		LOCAL="$(create_empty_file)"
 		>"$LOCAL"
 		rm_local=true
 	fi
 	if test "/dev/null" = "$REMOTE"
 	then
-		REMOTE="./p4merge-dev-null.REMOTE.$$"
+		REMOTE="$(create_empty_file)"
 		>"$REMOTE"
 		rm_remote=true
 	fi
@@ -33,3 +33,7 @@ merge_cmd () {
 	"$merge_tool_path" "$BASE" "$LOCAL" "$REMOTE" "$MERGED"
 	check_unchanged
 }
+
+create_empty_file () {
+	mktemp -t git-difftool-p4merge-empty-file.XXXXXX
+}
-- 
1.8.1.rc2.6.g18499ba