Allow brew update --rebase

Library/Contributions/manpages/brew.1.md

@@ -231,8 +231,11 @@ For the full command list, see the COMMANDS section.
     Unsymlink <formula> from the Homebrew prefix. This can be useful for
     temporarily disabling a formula: `brew unlink foo && commands && brew link foo`.
 
-  * `update`:
-    Fetch the newest version of Homebrew from GitHub using `git`(1).
+  * `update [--rebase]`:
+    Fetch the newest version of Homebrew and all formulae from GitHub using
+     `git`(1).
+
+    If --rebase is specified then `git pull --rebase` is used.
 
   * `upgrade` [<formulae>]:
     Upgrade outdated brews.

Library/Homebrew/cmd/update.rb

@@ -49,8 +49,11 @@ class RefreshBrew
           raise
         end
       end
+
       # specify a refspec so that 'origin/master' gets updated
-      execute "git pull origin refs/heads/master:refs/remotes/origin/master"
+      refspec = "refs/heads/master:refs/remotes/origin/master"
+      rebase = "--rebase" if ARGV.include? "--rebase"
+      execute "git pull #{rebase} origin #{refspec}"
       @current_revision = read_revision
     end
 

share/man/man1/brew.1

@@ -256,8 +256,11 @@ Example: \fBbrew install jruby && brew test jruby\fR
 Unsymlink \fIformula\fR from the Homebrew prefix\. This can be useful for temporarily disabling a formula: \fBbrew unlink foo && commands && brew link foo\fR\.
 .
 .TP
-\fBupdate\fR
-Fetch the newest version of Homebrew from GitHub using \fBgit\fR(1)\.
+\fBupdate [\-\-rebase]\fR
+Fetch the newest version of Homebrew and all formulae from GitHub using \fBgit\fR(1)\.
+.
+.IP
+If \-\-rebase is specified then \fBgit pull \-\-rebase\fR is used\.
 .
 .TP
 \fBupgrade\fR [\fIformulae\fR]