mergetools: create mergetool_find_win32_cmd() helper function for winmerge

Signed-off-by: Jacob Nisnevich <jacob.nisnevich@gmail.com>
Acked-by: David Aguilar <davvid@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/mergetools/winmerge b/mergetools/winmerge
index 74a66d4..f3819d3 100644
--- a/mergetools/winmerge
+++ b/mergetools/winmerge
@@ -13,24 +13,5 @@
 }
 
 translate_merge_tool_path() {
-	# Use WinMergeU.exe if it exists in $PATH
-	if type -p WinMergeU.exe >/dev/null 2>&1
-	then
-		printf WinMergeU.exe
-		return
-	fi
-
-	# Look for WinMergeU.exe in the typical locations
-	winmerge_exe="WinMerge/WinMergeU.exe"
-	for directory in $(env | grep -Ei '^PROGRAM(FILES(\(X86\))?|W6432)=' |
-		cut -d '=' -f 2- | sort -u)
-	do
-		if test -n "$directory" && test -x "$directory/$winmerge_exe"
-		then
-			printf '%s' "$directory/$winmerge_exe"
-			return
-		fi
-	done
-
-	printf WinMergeU.exe
+	mergetool_find_win32_cmd "WinMergeU.exe" "WinMerge"
 }