keg: handle the info directory file properly

If HOMEBREW_KEEP_INFO environment variable is set:
 - Do not symlink the info directory file (aka 'share/info/dir')
   otherwise it gets overwritten by next installed brew.
 - Install an entry in the directory for each linked info file when the
   brew is linked.
 - Uninstall the entry when the brew is unlinked.

Closes Homebrew/homebrew#9700.

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

Library/Contributions/manpages/brew.1.md

@@ -366,7 +366,10 @@ creating your own can be found on the wiki:
 
   * HOMEBREW\_KEEP\_INFO:
     If set, Homebrew will not remove files from `share/info`, allowing them
-    to be linked from the Cellar.
+    to be linked from the Cellar. To access these info files, prepend
+    `share/info` to your `INFOPATH` environment variable.
+
+    *Example:* `export INFOPATH='/usr/local/share/info:/usr/share/info'`
 
   * HOMEBREW\_MAKE\_JOBS:
     If set, instructs Homebrew to use the value of `HOMEBREW_MAKE_JOBS` as

Library/Homebrew/cleaner.rb

@@ -3,7 +3,14 @@ class Cleaner
     @f = Formula.factory f
     [f.bin, f.sbin, f.lib].select{ |d| d.exist? }.each{ |d| clean_dir d }
 
-    unless ENV['HOMEBREW_KEEP_INFO']
+    if ENV['HOMEBREW_KEEP_INFO']
+      # Get rid of the directory file, so it no longer bother us at link stage.
+      info_dir_file = f.info + 'dir'
+      if info_dir_file.file? and not f.skip_clean? info_dir_file
+        puts "rm #{info_dir_file}" if ARGV.verbose?
+        info_dir_file.unlink
+      end
+    else
       f.info.rmtree if f.info.directory? and not f.skip_clean? f.info
     end
 

Library/Homebrew/extend/pathname.rb

@@ -262,6 +262,20 @@ class Pathname
   ensure
     chmod saved_perms if saved_perms
   end
+
+  def install_info
+    unless self.symlink?
+      raise "Cannot install info entry for unbrewed info file '#{self}'"
+    end
+    system '/usr/bin/install-info', self.to_s, (self.dirname+'dir').to_s
+  end
+
+  def uninstall_info
+    unless self.symlink?
+      raise "Cannot uninstall info entry for unbrewed info file '#{self}'"
+    end
+    system '/usr/bin/install-info', '--delete', '--quiet', self.to_s, (self.dirname+'dir').to_s
+  end
 end
 
 # sets $n and $d so you can observe creation of stuff
@@ -286,6 +300,14 @@ module ObserverPathnameExtension
     puts "ln #{to_s}" if ARGV.verbose?
     $n+=1
   end
+  def install_info
+    super
+    puts "info #{to_s}" if ARGV.verbose?
+  end
+  def uninstall_info
+    super
+    puts "uninfo #{to_s}" if ARGV.verbose?
+  end
 end
 
 $n=0

Library/Homebrew/keg.rb

@@ -7,6 +7,8 @@ class Keg < Pathname
     raise "#{to_s} is not a directory" unless directory?
   end
 
+  INFOFILE_RX = %r[/share/info/[^.].*?\.info$]
+
   # if path is a file in a keg then this will return the containing Keg object
   def self.for path
     path = path.realpath
@@ -29,6 +31,7 @@ class Keg < Pathname
       next if src == self
       dst=HOMEBREW_PREFIX+src.relative_path_from(self)
       next unless dst.symlink?
+      dst.uninstall_info if dst.to_s =~ INFOFILE_RX and ENV['HOMEBREW_KEEP_INFO']
       dst.unlink
       n+=1
       Find.prune if src.directory?
@@ -127,7 +130,10 @@ protected
       dst.extend ObserverPathnameExtension
 
       if src.file?
+        # Do the symlink.
         dst.make_relative_symlink src unless File.basename(src) == '.DS_Store'
+        # Install info file entries in the info directory file
+        dst.install_info if dst.to_s =~ INFOFILE_RX and ENV['HOMEBREW_KEEP_INFO']
       elsif src.directory?
         # if the dst dir already exists, then great! walk the rest of the tree tho
         next if dst.directory? and not dst.symlink?

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" "January 2012" "Homebrew" "brew"
+.TH "BREW" "1" "February 2012" "Homebrew" "brew"
 .
 .SH "NAME"
 \fBbrew\fR \- The missing package manager for OS X
@@ -403,7 +403,10 @@ If set, Homebrew will use this editor when editing a single formula, or several
 .
 .TP
 HOMEBREW_KEEP_INFO
-If set, Homebrew will not remove files from \fBshare/info\fR, allowing them to be linked from the Cellar\.
+If set, Homebrew will not remove files from \fBshare/info\fR, allowing them to be linked from the Cellar\. To access these info files, prepend \fBshare/info\fR to your \fBINFOPATH\fR environment variable\.
+.
+.IP
+\fIExample:\fR \fBexport INFOPATH=\'/usr/local/share/info:/usr/share/info\'\fR
 .
 .TP
 HOMEBREW_MAKE_JOBS