Document brew diy in the man page

The documentation on this is hard to find, and awareness of the command
itself is pretty low. Which is too bad, because it's really handy and I
use it all the time myself.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>

Library/Contributions/manpages/brew.1.md

@@ -83,6 +83,15 @@ For the full command list, see the COMMANDS section.
 
     If `--all` is passed, show dependencies for all formulae.
 
+  * `diy [--set-name] [--set-version]`:
+    Automatically determine the installation prefix for non-Homebrew software.
+
+    Using the output from this command, you can install your own software into
+    the Cellar and then link it into Homebrew's prefix with `brew link`.
+
+    The options `--set-name` and `--set-version` each take an argument and allow
+    you to explicitly set the name and version of the package you are installing.
+
   * `doctor`:
     Check your system for potential problems. Doctor exits with a non-zero status
     if any problems are found.

share/man/man1/brew.1

@@ -94,6 +94,16 @@ If \fB\-n\fR is passed, show dependencies in topological order\.
 If \fB\-\-all\fR is passed, show dependencies for all formulae\.
 .
 .TP
+\fBdiy [\-\-set\-name] [\-\-set\-version]\fR
+Automatically determine the installation prefix for non\-Homebrew software\.
+.
+.IP
+Using the output from this command, you can install your own software into the Cellar and then link it into Homebrew\'s prefix with \fBbrew link\fR\.
+.
+.IP
+The options \fB\-\-set\-name\fR and \fB\-\-set\-version\fR each take an argument and allow you to explicitly set the name and version of the package you are installing\.
+.
+.TP
 \fBdoctor\fR
 Check your system for potential problems\. Doctor exits with a non\-zero status if any problems are found\.
 .