CommitGraphLoader: receive readChangedPaths as parameter

CommitGraphLoader: receive readChangedPaths as parameter

commitGraph.readChangedPaths controls the read of bloom filter
chunks from commit graph. CommitGraphLoader uses SystemReader
to read this conf, so it only sees its value when it is set in
$XDG_CONFIG_HOME/jgit/config (and not, for example, in the repo
config).

Pass the readChangedPaths value to the method that reads the commit
graph. Callers should read the value from the right configuration.

This change is a noop, but allows to move callers to the new method
progressively. Follow up changes will remove the previous method and
its usages.

Signed-off-by: Xing Huang <xingkhuang@google.com>
Change-Id: If10c9b758fbe0498c7bd1e6ac1cda8869682f16d