Ability to ignore a particular filename/path

[neilb]

Would be nice if you could also say "ignore any files/paths" matching this.

E.g. you could ask it to ignore ppport.h (wanted by @Leont)

[atoomic]

note: git grep is providing that feature
example:

# to ignore path like *.t and *.pm
> git grep test -- ':!*.t' ':!*.pm'

We can defintively add it

[khwilliamson]

All I need is #58.