build: check syntax of null plugins

Temporary hack to compute the number of commit in the branch

[skip appveyor]

linux_various/check_format.sh

@@ -1,19 +1,37 @@
-#!/bin/sh
+#!/bin/bash
+
+set -x
+# -e => need to handle empty $files variable
 
 ret=0
 
-branch=`git rev-parse --abbrev-ref HEAD`
-if [ x$branch = "xmaster" ]
-then
-    # check the last 20 commits. It ought to be enough even for big push
+# Doesn't work as travis only populate a single branch history
+
+#branch=`git rev-parse --abbrev-ref HEAD`
+#if [ x$branch = "xmaster" ]
+#then
+#    # check the last 20 commits. It ought to be enough even for big push
+#    diff_range=HEAD~20
+#else
+#    # check filed updated in the branch
+#    diff_range=master...HEAD
+#fi
+
+# Get the number of commits that share a linear history with the HEAD. Limit the value to 20
+# Solution isn't perfect but it ough to be close enough of the current branch size
+#
+# Picking more commits might hurt during the conversion. When everything will be ready, we
+# could get back to 20
+br_commit=`git log --oneline --decorate --graph -n 20 | grep "^\* [[:alnum:]]" -c`
+if [ $br_commit -lt 1 ]; then
+    # Something got wrong
     diff_range=HEAD~20
 else
-    # check filed updated in the branch
-    diff_range="master...HEAD"
+    diff_range=HEAD~$br_commit
 fi
 
 # get updates and blacklist directories that don't use yet the clang-format syntax
-files=`git diff $diff_range --name-only --diff-filter=ACMRT | \
+files=`git diff --name-only --diff-filter=ACMRT $diff_range  -- $PWD | \
     grep "\.\(c\|h\|inl\|cpp\|hpp\)$" | \
     grep -v "${1}common/" | \
     grep -v "${1}pcsx2/" | \
@@ -21,23 +39,16 @@ files=`git diff $diff_range --name-only --diff-filter=ACMRT | \
     grep -v "${1}plugins/CDVDiso/" | \
     grep -v "${1}plugins/CDVDisoEFP/" | \
     grep -v "${1}plugins/CDVDlinuz/" | \
-    grep -v "${1}plugins/CDVDnull/" | \
     grep -v "${1}plugins/CDVDolio/" | \
     grep -v "${1}plugins/CDVDpeops/" | \
     grep -v "${1}plugins/dev9ghzdrk/" | \
-    grep -v "${1}plugins/dev9null/" | \
-    grep -v "${1}plugins/FWnull/" | \
     grep -v "${1}plugins/GSdx/" | \
     grep -v "${1}plugins/GSdx_legacy/" | \
-    grep -v "${1}plugins/GSnull/" | \
     grep -v "${1}plugins/LilyPad/" | \
     grep -v "${1}plugins/onepad/" | \
-    grep -v "${1}plugins/PadNull/" | \
     grep -v "${1}plugins/PeopsSPU2/" | \
-    grep -v "${1}plugins/SPU2null/" | \
     grep -v "${1}plugins/spu2-x/" | \
     grep -v "${1}plugins/SSSPSXPAD/" | \
-    grep -v "${1}plugins/USBnull/" | \
     grep -v "${1}plugins/USBqemu/" | \
     grep -v "${1}plugins/xpad/" | \
     grep -v "${1}plugins/zerogs/" | \