Update repo hooks for media mainline repos

Change to the R branches; guidance to users when they need to override.
separate the list-of-files for partial repo (frameworks/av) from the script.
Also updates the configuration specific to frameworks/av as a repo split
between mainline/non.

Bug: 157501573
Test: various combinations of repo upload
Change-Id: I726f218c562ea151b4f76ded0903c68400a2f3fd
diff --git a/MainlineFiles.cfg b/MainlineFiles.cfg
new file mode 100644
index 0000000..37d714c
--- /dev/null
+++ b/MainlineFiles.cfg
@@ -0,0 +1,34 @@
+# 
+# mainline files for frameworks/av
+#
+# ignore comment (#) lines and blank lines
+# rest are path prefixes starting at root of the project
+# (so OWNERS, not frameworks/av/OWNERS)
+# 
+# path
+# INCLUDE path
+# EXCLUDE path
+#
+# 'path' and 'INCLUDE path' are identical -- they both indicate that this path
+# is part of mainline
+# EXCLUDE indicates that this is not part of mainline,
+# so 'foo/' and 'EXCLUDE foo/nope'
+# means everything under foo/ is part of mainline EXCEPT foo/nope.
+# INCLUDE/EXCLUDE/INCLUDE nested structuring is not supported
+#
+# matching is purely prefix
+# so 'foo' will match 'foo', 'foo.c', 'foo/bar/baz'
+# if you want to exclude a directory, best to use a pattern like "foo/"
+#
+
+media/codec2/components/
+media/codecs/
+media/extractors/
+media/libstagefright/codecs/amrnb/
+media/libstagefright/codecs/amrwb/
+media/libstagefright/codecs/amrwbenc/
+media/libstagefright/codecs/common/
+media/libstagefright/codecs/flac/
+media/libstagefright/codecs/m4v_h263/
+media/libstagefright/codecs/mp3dec/
+media/libstagefright/mpeg2ts