Use customized color for diff colorization. `<slot>` specifies
which part of the patch to use the specified color, and is one
of `plain` (context text), `meta` (metainformation), `frag`
- (hunk header), `old` (removed lines), `new` (added lines),
- `commit` (commit headers), or `whitespace` (highlighting
- whitespace errors). The values of these variables may be specified as
- in color.branch.<slot>.
+ (hunk header), 'func' (function in hunk header), `old` (removed lines),
+ `new` (added lines), `commit` (commit headers), or `whitespace`
+ (highlighting whitespace errors). The values of these variables may be
+ specified as in color.branch.<slot>.
color.grep::
When set to `always`, always highlight matches. When `false` (or