Introduce HOMEBREW_CURL_VERBOSE

When investigating issues, one might want to see exactly what curl is
doing behind the scenes. Setting HOMEBREW_CURL_VERBOSE will cause the
'--verbose' flag to be passed to all invocations of curl.

Prompted by Homebrew/homebrew#8992.

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

Library/Contributions/manpages/brew.1.md

@@ -336,6 +336,9 @@ creating your own can be found on the wiki:
     This can be used to keep downloads out of your home folder, if you have
     it mounted on an SSD or are using FileVault for instance.
 
+  * HOMEBREW\_CURL\_VERBOSE:
+    If set, Homebrew will pass `--verbose` when invoking `curl`(1).
+
   * HOMEBREW\_DEBUG:
     If set, instructs Homebrew to always assume `--debug` when running
     commands.

Library/Homebrew/utils.rb

@@ -111,6 +111,7 @@ def curl *args
   args = [HOMEBREW_CURL_ARGS, HOMEBREW_USER_AGENT, *args]
   # See https://github.com/mxcl/homebrew/issues/6103
   args << "--insecure" if MacOS.version < 10.6
+  args << "--verbose" if ENV['HOMEBREW_CURL_VERBOSE']
 
   safe_system curl, *args
 end

share/man/man1/brew.1

@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BREW" "1" "November 2011" "Homebrew" "brew"
+.TH "BREW" "1" "December 2011" "Homebrew" "brew"
 .
 .SH "NAME"
 \fBbrew\fR \- The missing package manager for OS X
@@ -376,6 +376,10 @@ If set, instructs Homebrew to use the give folder as the download cache\. Otherw
 This can be used to keep downloads out of your home folder, if you have it mounted on an SSD or are using FileVault for instance\.
 .
 .TP
+HOMEBREW_CURL_VERBOSE
+If set, Homebrew will pass \fB\-\-verbose\fR when invoking \fBcurl\fR(1)\.
+.
+.TP
 HOMEBREW_DEBUG
 If set, instructs Homebrew to always assume \fB\-\-debug\fR when running commands\.
 .