Modifying the source code of a home brew package

I installed a package with homebrew (qt). I'd like to modify the source code and rebuild the package. I can't seem to find the source code, though. brew --cache returns a directory that doesn't exist, and the code for qt isn't in /u开发者_StackOverflow中文版sr/local/Cellar. Am I missing something? Does homebrew remove the source code after the application is built?

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Homebrew only keeps binaries. If your Homebrew cache directory (which is normally at /Library/Caches/Homebrew, but can be found using brew --cache, as you noted) has been moved or deleted, then you'll have to get the source code again. You can grab just the source code with brew fetch qt.

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If you get only the source package, it may be missing the patch included in the formula and not exactly the source of the binary you are currently running. To get the source tree with the patch applied, you may do:

brew unpack --patch <formula>

From the man page:

   unpack [--git|--patch] [--destdir=path] formulae
          Unpack the source files for formulae into subdirectories of  the
          current  working directory. If --destdir=path is given, the sub-
          directories will be created in the  directory  named  by  <path>
          instead.

          If  --patch  is  passed, patches for formulae will be applied to
          the unpacked source.

          If --git is passed, a Git repository will be initalized  in  the
          unpacked  source.  This  is  useful for creating patches for the
          software.