hg diff takes 30 seconds to find nothing.

[Armando Singer]

> The wiki page is vague: will that tell it to ignore the "build" directory at
> the top level, or will it tell it to ignore every build directory in every
> subdirectory?  (If I had a source/build/ would that get ignored?)

globs or regexps are not rooted. 'build/' will ignore every build directory.
To match a particular directory, use the regext syntax to root it:

syntax: regexp
^build/$

I use the glob syntax as an easy way to ignore all matching files, such as:

syntax: glob
*~

http://www.selenic.com/mercurial/wiki/index.cgi/.hgignore

Armando