Add `brew linkage --cached` manpage output.

docs/Manpage.md

@@ -779,7 +779,7 @@ With `--verbose` or `-v`, many commands print extra debugging information. Note
     If `--pry` is passed or HOMEBREW_PRY is set, pry will be
     used instead of irb.
 
-  * `linkage` [`--test`] [`--reverse`] `formula`:
+  * `linkage` [`--test`] [`--reverse`] [`--cached`] `formula`:
     Checks the library links of an installed formula.
 
     Only works on installed formulae. An error is raised if it is run on
@@ -791,6 +791,9 @@ With `--verbose` or `-v`, many commands print extra debugging information. Note
     If `--reverse` is passed, print the dylib followed by the binaries
     which link to it for each library the keg references.
 
+    If `--cached` is passed, print the cached linkage values stored in
+    HOMEBREW_CACHE, set from a previous `brew linkage` run
+
   * `man` [`--fail-if-changed`]:
     Generate Homebrew's manpages.
 

manpages/brew-cask.1

 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BREW\-CASK" "1" "April 2018" "Homebrew" "brew-cask"
+.TH "BREW\-CASK" "1" "May 2018" "Homebrew" "brew-cask"
 .
 .SH "NAME"
 \fBbrew\-cask\fR \- a friendly binary installer for macOS

manpages/brew.1

 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BREW" "1" "April 2018" "Homebrew" "brew"
+.TH "BREW" "1" "May 2018" "Homebrew" "brew"
 .
 .SH "NAME"
 \fBbrew\fR \- The missing package manager for macOS
@@ -795,7 +795,7 @@ Enter the interactive Homebrew Ruby shell\.
 If \fB\-\-examples\fR is passed, several examples will be shown\. If \fB\-\-pry\fR is passed or HOMEBREW_PRY is set, pry will be used instead of irb\.
 .
 .TP
-\fBlinkage\fR [\fB\-\-test\fR] [\fB\-\-reverse\fR] \fIformula\fR
+\fBlinkage\fR [\fB\-\-test\fR] [\fB\-\-reverse\fR] [\fB\-\-cached\fR] \fIformula\fR
 Checks the library links of an installed formula\.
 .
 .IP
@@ -807,6 +807,9 @@ If \fB\-\-test\fR is passed, only display missing libraries and exit with a non\
 .IP
 If \fB\-\-reverse\fR is passed, print the dylib followed by the binaries which link to it for each library the keg references\.
 .
+.IP
+If \fB\-\-cached\fR is passed, print the cached linkage values stored in HOMEBREW_CACHE, set from a previous \fBbrew linkage\fR run
+.
 .TP
 \fBman\fR [\fB\-\-fail\-if\-changed\fR]
 Generate Homebrew\'s manpages\.