magit.el: execute git grep on toplevel directory

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
magit.el: use word-at-point as default input to grep

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Fix regression in `magit-refresh-wrapper' that caused status buffer to be refreshed twice.

This was introduced in 361f2d60: a manual conversion of `cl-adjoin'
missed a negation.
Merge pull request #635 from ncalexan/nalexander/refresh-regression

Fix regression that caused status buffer to be refreshed twice.
Merge commit '25b5f6e3ca7f9892ce607121aaf5c4409b994b19' into artagnon/grep
fix byte-compilation
Merge branch 'artagnon/grep'
Merge remote-tracking branch 'origin/master'