_sgbak folders hold the old versions in SourceGear's Vault directory. Ignoring it is the default behavior in ack. This is a pretty quick and dirty patch, and it seems like this will eventually go in the "huge-ass list of files we want to ignore by default". I dunno if you really want this, but I needed it and figured I'd throw it out there.
ignores _sgbak (Vault) folders by default
Whoops, left in a printf. One sec.
changed printf to debug log
First, thanks for submitting this pull request. I like it when people err on the side of contributing code rather than hoarding it.
That said, I don't want to merge it, for several reasons. I do need to make some better defaults for ignoring files, but I don't think hard-coded strcmp()s are the way to go. Also, your patch will ignore _sgbak even if ag is run with -u for unrestricted searches.
I don't know if you already know this, but if you want to ignore files you can put patterns in a .agignore file. It works just like git's .gitignore and Mercurial's .hgignore.
No problem. Thanks for the feedback :)