Don't warn for broken ignore syntax

[bluss]

Example case:

$ rg SliceRef
<some directory>/.gitignore: line 2: error parsing glob '**.DS_Store': invalid use of **; must be one path component

My idea here is that I'm interested in help searching through a hairy mess of files. The syntax errors are not interesting, in that case, it's from some checked-out code that I don't know anything about anymore.

The errant line seems to be this:

**.DS_Store

• Ripgrep version: 0.6.0 from crates.io

[BurntSushi]

There's a little discussion on this in #373, where I in particular suggest the use of --no-messages.

I don't agree with completely suppressing gitignore errors, since I think they are useful for diagnosing .gitignore problems. Notably, git doesn't report any errors, it just silently ignores bad patterns and I've seen more than a few cases where ripgrep made folks realize that their .gitignore files were actually wrong!

[FSMaxB]

Quick workaround: rg SliceRef 2> /dev/null

The error messages are written to stderr, so you can just suppress them like that.

[bluss]

--no-messages is a good existing workaround too. I'll just research what else I might be missing with it.

[BurntSushi]

@bluss Have you amassed any more thoughts on this topic? Every time I look at this issue, I wonder how it can be closed, but I am myself torn on it. On the one hand, it surfaces invalid gitignores, on the other hand, it's frustrating if those gitignores aren't your own.