Man page: clarify `list` command

Document the '--versions' option for `brew list`.
The two forms of the `list` command as previously documented clearly do
different things, but after documenting '--versions', their functions do
overlap a bit, so we combine them and clarify the different invocations.

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

Library/Contributions/manpages/brew.1.md

@@ -164,11 +164,13 @@ For the full command list, see the COMMANDS section.
     is done automatically when you install formula, but can be useful for DIY
     installations.
 
-  * `list`:
-    List all installed formulae.
+  * `list [--versions]` [<formulae>]:
+    Without any arguments, list all installed formulae.
+
+    If <formulae> are given, list the installed files for <formulae>.
 
-  * `list` <formula>:
-    List the installed files for <formula>.
+    If `--versions` is passed, show the version number for installed formulae,
+    or only the specified formulae if <formulae> are given.
 
   * `log [git-log-options]` <formula> ...:
     Show the git log for the given formulae. Options that `git-log`(1)

share/man/man1/brew.1

@@ -181,12 +181,14 @@ If \fB\-\-git\fR is passed, Homebrew will create a Git repository, useful for cr
 Symlink all of \fIformula\fR\'s installed files into the Homebrew prefix\. This is done automatically when you install formula, but can be useful for DIY installations\.
 .
 .TP
-\fBlist\fR
-List all installed formulae\.
+\fBlist [\-\-versions]\fR [\fIformulae\fR]
+Without any arguments, list all installed formulae\.
 .
-.TP
-\fBlist\fR \fIformula\fR
-List the installed files for \fIformula\fR\.
+.IP
+If \fIformulae\fR are given, list the installed files for \fIformulae\fR\.
+.
+.IP
+If \fB\-\-versions\fR is passed, show the version number for installed formulae, or only the specified formulae if \fIformulae\fR are given\.
 .
 .TP
 \fBlog [git\-log\-options]\fR \fIformula\fR \.\.\.