Merge branch 'zk/difftool-counts'

Show the total number of paths and the number of paths shown so far
when "git difftool" prompts to launch an external diff tool, which
would give users some sense of progress.

* zk/difftool-counts:
diff.c: fix some recent whitespace style violations
difftool: display the number of files in the diff queue in the prompt

diff --cc Documentation/git.txt
Simple merge

diff --cc diff.c
Simple merge

diff --cc diff.h
Simple merge