diff --git a/autoload/xolox/misc/buffer.vim b/autoload/xolox/misc/buffer.vim
index 3597cc2..01dca6e 100644
--- a/autoload/xolox/misc/buffer.vim
+++ b/autoload/xolox/misc/buffer.vim
@@ -1,15 +1,44 @@
-" Vim auto-load script
+" Handling of special buffers
+"
 " Author: Peter Odding <peter@peterodding.com>
-" Last Change: April 18, 2013
+" Last Change: May 19, 2013
 " URL: http://peterodding.com/code/vim/misc/
+"
+" The functions defined here make it easier to deal with special Vim buffers
+" that contain text generated by a Vim plug-in. For example my [vim-notes
+" plug-in] [vim-notes] generates several such buffers:
+"
+" - [:RecentNotes] [RecentNotes] lists recently modified notes
+" - [:ShowTaggedNotes] [ShowTaggedNotes] lists notes grouped by tags
+" - etc.
+"
+" Because the text in these buffers is generated, Vim shouldn't bother with
+" swap files and it should never prompt the user whether to save changes to
+" the generated text.
+"
+" [vim-notes]: http://peterodding.com/code/vim/notes/
+" [RecentNotes]: http://peterodding.com/code/vim/notes/#recentnotes_command
+" [ShowTaggedNotes]: http://peterodding.com/code/vim/notes/#showtaggednotes_command
 
 function! xolox#misc#buffer#is_empty() " {{{1
-  " Check if the current buffer is an empty, unchanged buffer which can be reused.
+  " Checks if the current buffer is an empty, unchanged buffer which can be
+  " reused. Returns 1 if an empty buffer is found, 0 otherwise.
   return !&modified && expand('%') == '' && line('$') <= 1 && getline(1) == ''
 endfunction
 
 function! xolox#misc#buffer#prepare(...) " {{{1
-  " Open a special buffer (with generated contents, not directly edited by the user).
+  " Open a special buffer, i.e. a buffer that will hold generated contents,
+  " not directly edited by the user. The buffer can be customized by passing a
+  " dictionary with the following key/value pairs as the first argument:
+  "
+  " - **name** (required): The base name of the buffer (i.e. the base name of
+  "   the file loaded in the buffer, even though it isn't really a file and
+  "   nothing is really 'loaded' :-)
+  " - **path** (required): The pathname of the buffer. May be relevant if
+  "   [:lcd] [lcd] or ['autochdir'] [acd] is being used.
+  "
+  " [lcd]: http://vimdoc.sourceforge.net/htmldoc/editing.html#:lcd
+  " [acd]: http://vimdoc.sourceforge.net/htmldoc/options.html#'autochdir'
   if a:0 == 1 && type(a:1) == type('')
     " Backwards compatibility with old interface.
     let options = {'name': a:1, 'path': a:1}
@@ -41,7 +70,7 @@ function! xolox#misc#buffer#prepare(...) " {{{1
 endfunction
 
 function! xolox#misc#buffer#lock() " {{{1
-  " Lock a special buffer so it can no longer be edited.
+  " Lock a special buffer so that its contents can no longer be edited.
   setlocal readonly nomodifiable nomodified
 endfunction
 
diff --git a/autoload/xolox/misc/compat.vim b/autoload/xolox/misc/compat.vim
index 70a4287..3f3a42c 100644
--- a/autoload/xolox/misc/compat.vim
+++ b/autoload/xolox/misc/compat.vim
@@ -1,22 +1,36 @@
-" Vim auto-load script
+" Compatibility checking.
+"
 " Author: Peter Odding <peter@peterodding.com>
-" Last Change: May 13, 2013
+" Last Change: May 20, 2013
 " URL: http://peterodding.com/code/vim/misc/
-
-" The following integer will be bumped whenever a change in the miscellaneous
+"
+" This Vim script defines a version number for the miscellaneous scripts. Each
+" of my plug-ins compares their expected version of the miscellaneous scripts
+" against the version number defined inside the miscellaneous scripts.
+"
+" The version number is incremented whenever a change in the miscellaneous
 " scripts breaks backwards compatibility. This enables my Vim plug-ins to fail
 " early when they detect an incompatible version, instead of breaking at the
 " worst possible moments :-).
-let g:xolox#misc#compat#version = 3
+let g:xolox#misc#compat#version = 7
 
 " Remember the directory where the miscellaneous scripts are loaded from
 " so the user knows which plug-in to update if incompatibilities arise.
-let s:misc_directory = fnamemodify(expand('<sfile>'), ':p:h')
+let s:misc_directory = fnamemodify(expand('<sfile>'), ':~:h')
 
-function! xolox#misc#compat#check(plugin_name, required_version)
+function! xolox#misc#compat#check(plugin_name, plugin_version, required_version)
+  " Expects three arguments:
+  "
+  " 1. The name of the Vim plug-in that is using the miscellaneous scripts
+  " 2. The version of the Vim plug-in that is using the miscellaneous scripts
+  " 3. The version of the miscellaneous scripts expected by the plug-in
+  "
+  " When the loaded version of the miscellaneous scripts is different from the
+  " version expected by the plug-in, this function will raise an error message
+  " that explains what went wrong.
   if a:required_version != g:xolox#misc#compat#version
-    let msg = "The %s plug-in requires version %i of the miscellaneous scripts, however version %i was loaded from %s!"
-    throw printf(msg, a:plugin_name, a:required_version, g:xolox#misc#compat#version, s:misc_directory)
+    let msg = "The %s %s plug-in expects version %i of the miscellaneous scripts, however version %i was loaded from the directory %s! Please upgrade your plug-ins to the latest releases to resolve this problem."
+    throw printf(msg, a:plugin_name, a:plugin_version, a:required_version, g:xolox#misc#compat#version, s:misc_directory)
   endif
 endfunction
 
diff --git a/autoload/xolox/misc/complete.vim b/autoload/xolox/misc/complete.vim
index 2ada676..763e0b9 100644
--- a/autoload/xolox/misc/complete.vim
+++ b/autoload/xolox/misc/complete.vim
@@ -1,11 +1,15 @@
-" Vim auto-load script
+" Tab completion for user defined commands.
+"
 " Author: Peter Odding <peter@peterodding.com>
-" Last Change: March 15, 2011
+" Last Change: May 19, 2013
 " URL: http://peterodding.com/code/vim/misc/
 
-" Keyword completion from the current buffer for user defined commands.
-
 function! xolox#misc#complete#keywords(arglead, cmdline, cursorpos)
+  " This function can be used to perform keyword completion for user defined
+  " Vim commands based on the contents of the current buffer. Here's an
+  " example of how you would use it:
+  "
+  "     :command -nargs=* -complete=customlist,xolox#misc#complete#keywords MyCmd call s:MyCmd(<f-args>)
   let words = {}
   for line in getline(1, '$')
     for word in split(line, '\W\+')
diff --git a/autoload/xolox/misc/escape.vim b/autoload/xolox/misc/escape.vim
index 1dd1838..29a16ca 100644
--- a/autoload/xolox/misc/escape.vim
+++ b/autoload/xolox/misc/escape.vim
@@ -1,11 +1,16 @@
-" Vim auto-load script
+" String escaping functions.
+"
 " Author: Peter Odding <peter@peterodding.com>
-" Last Change: November 21, 2011
+" Last Change: May 19, 2013
 " URL: http://peterodding.com/code/vim/misc/
 
-" Convert a string into a :substitute pattern that matches the string literally.
-
-function! xolox#misc#escape#pattern(string)
+function! xolox#misc#escape#pattern(string) " {{{1
+  " Takes a single string argument and converts it into a [:substitute]
+  " [subcmd] / [substitute()] [subfun] pattern string that matches the given
+  " string literally.
+  "
+  " [subfun]: http://vimdoc.sourceforge.net/htmldoc/eval.html#substitute()
+  " [subcmd]: http://vimdoc.sourceforge.net/htmldoc/change.html#:substitute
   if type(a:string) == type('')
     let string = escape(a:string, '^$.*\~[]')
     return substitute(string, '\n', '\\n', 'g')
@@ -13,9 +18,10 @@ function! xolox#misc#escape#pattern(string)
   return ''
 endfunction
 
-" Convert a string into a :substitute replacement that inserts the string literally.
-
-function! xolox#misc#escape#substitute(string)
+function! xolox#misc#escape#substitute(string) " {{{1
+  " Takes a single string argument and converts it into a [:substitute]
+  " [subcmd] / [substitute()] [subfun] replacement string that inserts the
+  " given string literally.
   if type(a:string) == type('')
     let string = escape(a:string, '\&~%')
     return substitute(string, '\n', '\\r', 'g')
@@ -23,13 +29,17 @@ function! xolox#misc#escape#substitute(string)
   return ''
 endfunction
 
-" Convert a string into a quoted command line argument. I was going to add a
-" long rant here about &shellslash, but really, it won't make any difference.
-" Let's just suffice to say that I have yet to encounter a single person out
-" there who uses this option for its intended purpose (running a UNIX-style
-" shell on Windows).
-
-function! xolox#misc#escape#shell(string)
+function! xolox#misc#escape#shell(string) " {{{1
+  " Takes a single string argument and converts it into a quoted command line
+  " argument.
+  "
+  " I was going to add a long rant here about Vim's ['shellslash' option]
+  " [shellslash], but really, it won't make any difference. Let's just suffice
+  " to say that I have yet to encounter a single person out there who uses
+  " this option for its intended purpose (running a UNIX style shell on
+  " Microsoft Windows).
+  "
+  " [shellslash]: http://vimdoc.sourceforge.net/htmldoc/options.html#'shellslash'
   if xolox#misc#os#is_win()
     try
       let ssl_save = &shellslash
diff --git a/autoload/xolox/misc/list.vim b/autoload/xolox/misc/list.vim
index ee243d4..13dfb43 100644
--- a/autoload/xolox/misc/list.vim
+++ b/autoload/xolox/misc/list.vim
@@ -1,19 +1,27 @@
-" Vim auto-load script
+" List handling functions.
+"
 " Author: Peter Odding <peter@peterodding.com>
-" Last Change: August 31, 2011
+" Last Change: May 19, 2013
 " URL: http://peterodding.com/code/vim/misc/
 
-" Remove duplicate values from {list} in-place (preserves order).
-
-function! xolox#misc#list#unique(list)
+function! xolox#misc#list#unique(list) " {{{1
+  " Remove duplicate values from the given list in-place (preserves order).
   call reverse(a:list)
   call filter(a:list, 'count(a:list, v:val) == 1')
   return reverse(a:list)
 endfunction
 
-" Binary insertion (more efficient than calling sort() after each insertion).
-
-function! xolox#misc#list#binsert(list, value, ...)
+function! xolox#misc#list#binsert(list, value, ...) " {{{1
+  " Performs in-place binary insertion, which depending on your use case can
+  " be more efficient than calling Vim's [sort()] [sort] function after each
+  " insertion (in cases where a single, final sort is not an option). Expects
+  " three arguments:
+  "
+  " 1. A list
+  " 2. A value to insert
+  " 3. 1 (true) when case should be ignored, 0 (false) otherwise
+  "
+  " [sort]: http://vimdoc.sourceforge.net/htmldoc/eval.html#sort()
   let idx = s:binsert_r(a:list, 0, len(a:list), a:value, exists('a:1') && a:1)
   return insert(a:list, a:value, idx)
 endfunction
diff --git a/autoload/xolox/misc/msg.vim b/autoload/xolox/misc/msg.vim
index 9ba2b7c..38eb474 100644
--- a/autoload/xolox/misc/msg.vim
+++ b/autoload/xolox/misc/msg.vim
@@ -1,6 +1,7 @@
-" Vim auto-load script
+" Functions to interact with the user.
+"
 " Author: Peter Odding <peter@peterodding.com>
-" Last Change: March 15, 2011
+" Last Change: May 19, 2013
 " URL: http://peterodding.com/code/vim/misc/
 
 if !exists('g:xolox_message_buffer')
@@ -12,29 +13,34 @@ if !exists('g:xolox_messages')
   let g:xolox_messages = []
 endif
 
-" Show a formatted informational message to the user.
-
-function! xolox#misc#msg#info(...)
+function! xolox#misc#msg#info(...) " {{{1
+  " Show a formatted informational message to the user. This function has the
+  " same argument handling as Vim's [printf()] [printf] function.
+  "
+  " [printf]: http://vimdoc.sourceforge.net/htmldoc/eval.html#printf()
   call s:show_message('title', a:000)
 endfunction
 
-" Show a formatted warning message to the user.
-
-function! xolox#misc#msg#warn(...)
+function! xolox#misc#msg#warn(...) " {{{1
+  " Show a formatted warning message to the user. This function has the same
+  " argument handling as Vim's [printf()] [printf] function.
   call s:show_message('warningmsg', a:000)
 endfunction
 
-" Show a formatted debugging message to the user?
-
-function! xolox#misc#msg#debug(...)
+function! xolox#misc#msg#debug(...) " {{{1
+  " Show a formatted debugging message to the user, if the user has enabled
+  " increased verbosity by setting Vim's ['verbose'] [verbose] option to one
+  " (1) or higher. This function has the same argument handling as Vim's
+  " [printf()] [printf] function.
+  "
+  " [verbose]: http://vimdoc.sourceforge.net/htmldoc/options.html#'verbose'
   if &vbs >= 1
     call s:show_message('question', a:000)
   endif
 endfunction
 
-" The implementation of info() and warn().
-
-function! s:show_message(hlgroup, args)
+function! s:show_message(hlgroup, args) " {{{1
+  " The implementation of info() and warn().
   let nargs = len(a:args)
   if nargs == 1
     let message = a:args[0]
@@ -56,7 +62,10 @@ function! s:show_message(hlgroup, args)
       augroup END
       execute 'echohl' a:hlgroup
       " Redraw to avoid |hit-enter| prompt.
-      redraw | echomsg message
+      redraw
+      for line in split(message, "\n")
+        echomsg line
+      endfor
       if g:xolox_message_buffer > 0
         call add(g:xolox_messages, message)
         if len(g:xolox_messages) > g:xolox_message_buffer
@@ -70,7 +79,8 @@ function! s:show_message(hlgroup, args)
   endif
 endfunction
 
-function! s:clear_message()
+function! s:clear_message() " {{{1
+  " Callback to clear message after some time has passed.
   echo ''
   let &more = s:more_save
   let &showmode = s:smd_save
diff --git a/autoload/xolox/misc/open.vim b/autoload/xolox/misc/open.vim
index 1fb24e0..b369f4f 100644
--- a/autoload/xolox/misc/open.vim
+++ b/autoload/xolox/misc/open.vim
@@ -1,6 +1,7 @@
-" Vim auto-load script
+" Integration between Vim and its environment.
+"
 " Author: Peter Odding <peter@peterodding.com>
-" Last Change: November 21, 2011
+" Last Change: May 19, 2013
 " URL: http://peterodding.com/code/vim/misc/
 
 if !exists('s:version')
@@ -9,7 +10,20 @@ if !exists('s:version')
   let s:handlers = ['gnome-open', 'kde-open', 'exo-open', 'xdg-open']
 endif
 
-function! xolox#misc#open#file(path, ...)
+function! xolox#misc#open#file(path, ...) " {{{1
+  " Given a pathname as the first argument, this opens the file with the
+  " program associated with the file type. So for example a text file might
+  " open in Vim, an `*.html` file would probably open in your web browser and
+  " a media file would open in a media player.
+  "
+  " This should work on Windows, Mac OS X and most Linux distributions. If
+  " this fails to find a file association, you can pass one or more external
+  " commands to try as additional arguments. For example:
+  "
+  "     :call xolox#misc#open#file('/path/to/my/file', 'firefox', 'google-chrome')
+  "
+  " This generally shouldn't be necessary but it might come in handy now and
+  " then.
   if xolox#misc#os#is_win()
     try
       call xolox#shell#open_with_windows_shell(a:path)
@@ -35,7 +49,15 @@ function! xolox#misc#open#file(path, ...)
   throw printf(s:enoimpl, s:script, 'xolox#misc#open#file')
 endfunction
 
-function! xolox#misc#open#url(url)
+function! xolox#misc#open#url(url) " {{{1
+  " Given a URL as the first argument, this opens the URL in your preferred or
+  " best available web browser:
+  "
+  " - In GUI environments a graphical web browser will open (or a new tab will
+  "   be created in an existing window)
+  " - In console Vim without a GUI environment, when you have any of `lynx`,
+  "   `links` or `w3m` installed it will launch a command line web browser in
+  "   front of Vim (temporarily suspending Vim)
   let url = a:url
   if url !~ '^\w\+://'
     if url !~ '@'
@@ -56,7 +78,7 @@ function! xolox#misc#open#url(url)
   call xolox#misc#open#file(url, 'firefox', 'google-chrome')
 endfunction
 
-function! s:handle_error(cmd, output)
+function! s:handle_error(cmd, output) " {{{1
   if v:shell_error
     let message = "open.vim %s: Failed to execute program! (command line: %s%s)"
     let output = strtrans(xolox#misc#str#trim(a:output))
diff --git a/autoload/xolox/misc/option.vim b/autoload/xolox/misc/option.vim
index efaf1bc..fce155c 100644
--- a/autoload/xolox/misc/option.vim
+++ b/autoload/xolox/misc/option.vim
@@ -1,9 +1,18 @@
-" Vim auto-load script
+" Vim and plug-in option handling.
+"
 " Author: Peter Odding <peter@peterodding.com>
-" Last Change: August 31, 2011
+" Last Change: May 19, 2013
 " URL: http://peterodding.com/code/vim/misc/
 
-function! xolox#misc#option#get(name, ...)
+function! xolox#misc#option#get(name, ...) " {{{1
+  " Expects one or two arguments: 1. The name of a variable and 2. the default
+  " value if the variable does not exist.
+  "
+  " Returns the value of the variable from a buffer local variable, global
+  " variable or the default value, depending on which is defined.
+  "
+  " This is used by some of my Vim plug-ins for option handling, so that users
+  " can customize options for specific buffers.
   if exists('b:' . a:name)
     " Buffer local variable.
     return eval('b:' . a:name)
@@ -16,9 +25,17 @@ function! xolox#misc#option#get(name, ...)
   endif
 endfunction
 
-" Functions to parse multi-valued Vim options like &tags and &runtimepath.
-
-function! xolox#misc#option#split(value)
+function! xolox#misc#option#split(value) " {{{1
+  " Given a multi-value Vim option like ['runtimepath'] [rtp] this returns a
+  " list of strings. For example:
+  "
+  "     :echo xolox#misc#option#split(&runtimepath)
+  "     ['/home/peter/Projects/Vim/misc',
+  "      '/home/peter/Projects/Vim/colorscheme-switcher',
+  "      '/home/peter/Projects/Vim/easytags',
+  "      ...]
+  "
+  " [rtp]: http://vimdoc.sourceforge.net/htmldoc/options.html#'runtimepath'
   let values = split(a:value, '[^\\]\zs,')
   return map(values, 's:unescape(v:val)')
 endfunction
@@ -27,7 +44,10 @@ function! s:unescape(s)
   return substitute(a:s, '\\\([\\,]\)', '\1', 'g')
 endfunction
 
-function! xolox#misc#option#join(values)
+function! xolox#misc#option#join(values) " {{{1
+  " Given a list of strings like the ones returned by
+  " `xolox#misc#option#split()`, this joins the strings together into a
+  " single value that can be used to set a Vim option.
   let values = copy(a:values)
   call map(values, 's:escape(v:val)')
   return join(values, ',')
@@ -37,7 +57,11 @@ function! s:escape(s)
   return escape(a:s, ',\')
 endfunction
 
-function! xolox#misc#option#split_tags(value)
+function! xolox#misc#option#split_tags(value) " {{{1
+  " Customized version of `xolox#misc#option#split()` with specialized
+  " handling for Vim's ['tags' option] [tags].
+  "
+  " [tags]: http://vimdoc.sourceforge.net/htmldoc/options.html#'tags'
   let values = split(a:value, '[^\\]\zs,')
   return map(values, 's:unescape_tags(v:val)')
 endfunction
@@ -46,7 +70,9 @@ function! s:unescape_tags(s)
   return substitute(a:s, '\\\([\\, ]\)', '\1', 'g')
 endfunction
 
-function! xolox#misc#option#join_tags(values)
+function! xolox#misc#option#join_tags(values) " {{{1
+  " Customized version of `xolox#misc#option#join()` with specialized
+  " handling for Vim's ['tags' option] [tags].
   let values = copy(a:values)
   call map(values, 's:escape_tags(v:val)')
   return join(values, ',')
@@ -56,9 +82,14 @@ function! s:escape_tags(s)
   return escape(a:s, ', ')
 endfunction
 
-function! xolox#misc#option#eval_tags(value, ...)
+function! xolox#misc#option#eval_tags(value, ...) " {{{1
+  " Evaluate Vim's ['tags' option] [tags] without looking at the file
+  " system, i.e. this will report tags files that don't exist yet. Expects
+  " the value of the ['tags' option] [tags] as the first argument. If the
+  " optional second argument is 1 (true) only the first match is returned,
+  " otherwise (so by default) a list with all matches is returned.
   let pathnames = []
-  let first_only = exists('a:1') && a:1
+  let first_only = exists('a:1') ? a:1 : 0
   for pattern in xolox#misc#option#split_tags(a:value)
     " Make buffer relative pathnames absolute.
     if pattern =~ '^\./'
@@ -78,7 +109,7 @@ function! xolox#misc#option#eval_tags(value, ...)
       return pathnames[0]
     endif
   endfor
-  return firstonly ? '' : pathnames
+  return first_only ? '' : pathnames
 endfunction
 
 " vim: ts=2 sw=2 et
diff --git a/autoload/xolox/misc/os.vim b/autoload/xolox/misc/os.vim
index ef036df..4dcf64d 100644
--- a/autoload/xolox/misc/os.vim
+++ b/autoload/xolox/misc/os.vim
@@ -1,19 +1,44 @@
-" Vim auto-load script
+" Operating system interfaces.
+"
 " Author: Peter Odding <peter@peterodding.com>
-" Last Change: May 13, 2013
+" Last Change: May 19, 2013
 " URL: http://peterodding.com/code/vim/misc/
 
-let g:xolox#misc#os#version = '0.2'
+let g:xolox#misc#os#version = '0.3'
 
 function! xolox#misc#os#is_win() " {{{1
-  " Check whether Vim is running on Microsoft Windows.
+  " Returns 1 (true) when on Microsoft Windows, 0 (false) otherwise.
   return has('win16') || has('win32') || has('win64')
 endfunction
 
 function! xolox#misc#os#exec(options) " {{{1
-  " Execute an external command (hiding the console on Windows when possible).
-  " NB: Everything below is wrapped in a try/finally block to guarantee
-  " cleanup of temporary files.
+  " Execute an external command (hiding the console on Microsoft Windows when
+  " my [vim-shell plug-in] [vim-shell] is installed).
+  "
+  " Expects a dictionary with the following key/value pairs as the first
+  " argument:
+  "
+  " - **command** (required): The command line to execute
+  " - **async** (optional): set this to 1 (true) to execute the command in the
+  "   background (asynchronously)
+  " - **stdin** (optional): a string or list of strings with the input for the
+  "   external command
+  " - **check** (optional): set this to 0 (false) to disable checking of the
+  "   exit code of the external command (by default an exception will be
+  "   raised when the command fails)
+  "
+  " Returns a dictionary with one or more of the following key/value pairs:
+  "
+  " - **command** (always available): the generated command line that was used
+  "   to run the external command
+  " - **exit_code** (only in synchronous mode): the exit status of the
+  "   external command (an integer, zero on success)
+  " - **stdout** (only in synchronous mode): the output of the command on the
+  "   standard output stream (a list of strings, one for each line)
+  " - **stderr** (only in synchronous mode): the output of the command on the
+  "   standard error stream (as a list of strings, one for each line)
+  "
+  " [vim-shell]: http://peterodding.com/code/vim/shell/
   try
 
     " Unpack the options.
@@ -72,6 +97,14 @@ function! xolox#misc#os#exec(options) " {{{1
         endif
       endif
 
+      " Execute the command line using 'sh' instead of the default shell,
+      " because we assume that standard output and standard error can be
+      " redirected separately, but (t)csh does not support this.
+      if has('unix')
+        call xolox#misc#msg#debug("os.vim %s: Generated shell expression: %s", g:xolox#misc#os#version, cmd)
+        let cmd = printf('sh -c %s', xolox#misc#escape#shell(cmd))
+      endif
+
       " Let the user know what's happening (in case they're interested).
       call xolox#misc#msg#debug("os.vim %s: Executing external command using system() function: %s", g:xolox#misc#os#version, cmd)
       call system(cmd)
@@ -79,19 +112,29 @@ function! xolox#misc#os#exec(options) " {{{1
 
     endif
 
-    let result = {}
+    " Return the results as a dictionary with one or more key/value pairs.
+    let result = {'command': cmd}
     if !async
+      let result['exit_code'] = exit_code
+      let result['stdout'] = s:readfile(tempout)
+      let result['stderr'] = s:readfile(temperr)
       " If we just executed a synchronous command and the caller didn't
       " specifically ask us *not* to check the exit code of the external
       " command, we'll do so now.
       if get(a:options, 'check', 1) && exit_code != 0
-        let msg = "os.vim %s: External command failed with exit code %d: %s"
-        throw printf(msg, g:xolox#misc#os#version, result['exit_code'], result['command'])
+        " Prepare an error message with enough details so the user can investigate.
+        let msg = printf("os.vim %s: External command failed with exit code %d!", g:xolox#misc#os#version, result['exit_code'])
+        let msg .= printf("\nCommand line: %s", result['command'])
+        " If the external command reported an error, we'll include it in our message.
+        if !empty(result['stderr'])
+          " This is where we would normally expect to find an error message.
+          let msg .= printf("\nOutput on standard output stream:\n%s", join(result['stderr'], "\n"))
+        elseif !empty(result['stdout'])
+          " Exuberant Ctags on Windows XP reports errors on standard output :-x.
+          let msg .= printf("\nOutput on standard error stream:\n%s", join(result['stdout'], "\n"))
+        endif
+        throw msg
       endif
-      " Return the results as a dictionary with three key/value pairs.
-      let result['exit_code'] = exit_code
-      let result['stdout'] = s:readfile(tempout)
-      let result['stderr'] = s:readfile(temperr)
     endif
     return result
 
diff --git a/autoload/xolox/misc/path.vim b/autoload/xolox/misc/path.vim
index 6ad8be4..15e11d6 100644
--- a/autoload/xolox/misc/path.vim
+++ b/autoload/xolox/misc/path.vim
@@ -1,53 +1,72 @@
-" Vim auto-load script
+" Pathname manipulation functions.
+"
 " Author: Peter Odding <peter@peterodding.com>
-" Last Change: April 28, 2013
+" Last Change: May 19, 2013
 " URL: http://peterodding.com/code/vim/misc/
 
 let s:windows_compatible = has('win32') || has('win64')
 let s:mac_os_x_compatible = has('macunix')
 
 function! xolox#misc#path#which(...) " {{{1
-  " Scan the executable search path for programs.
+  " Scan the executable search path (`$PATH`) for one or more external
+  " programs. Expects one or more string arguments with program names. Returns
+  " a list with the absolute pathnames of all found programs. Here's an
+  " example:
+  "
+  "     :echo xolox#misc#path#which('gvim', 'vim')
+  "     ['/usr/local/bin/gvim',
+  "      '/usr/bin/gvim',
+  "      '/usr/local/bin/vim',
+  "      '/usr/bin/vim']
   let extensions = s:windows_compatible ? split($PATHEXT, ';') : ['']
   let matches = []
   let checked = {}
-  for directory in split($PATH, s:windows_compatible ? ';' : ':')
-    let directory = xolox#misc#path#absolute(directory)
-    if !has_key(checked, directory)
-      if isdirectory(directory)
-        for program in a:000
-          for extension in extensions
-            let path = xolox#misc#path#merge(directory, program . extension)
-            if executable(path)
-              call add(matches, path)
-            endif
-          endfor
-        endfor
-      endif
-      let checked[directory] = 1
-    endif
+  for program in a:000
+    for extension in extensions
+      for directory in split($PATH, s:windows_compatible ? ';' : ':')
+        let directory = xolox#misc#path#absolute(directory)
+        if isdirectory(directory)
+          let path = xolox#misc#path#merge(directory, program . extension)
+          if executable(path)
+            call add(matches, path)
+          endif
+        endif
+      endfor
+    endfor
   endfor
   return matches
 endfunction
 
 function! xolox#misc#path#split(path) " {{{1
-  " Split a pathname into a list of path components.
+  " Split a pathname (the first and only argument) into a list of pathname
+  " components.
+  "
+  " On Windows, pathnames starting with two slashes or backslashes are UNC
+  " paths where the leading slashes are significant... In this case we split
+  " like this:
+  "
+  " - Input: `'//server/share/directory'`
+  " - Result: `['//server', 'share', 'directory']`
+  "
+  " Everything except Windows is treated like UNIX until someone has a better
+  " suggestion :-). In this case we split like this:
+  "
+  " - Input: `'/foo/bar/baz'`
+  " - Result: `['/', 'foo', 'bar', 'baz']`
+  "
+  " To join a list of pathname components back into a single pathname string,
+  " use the `xolox#misc#path#join()` function.
   if type(a:path) == type('')
     if s:windows_compatible
       if a:path =~ '^[\/][\/]'
-        " On Windows, pathnames starting with two slashes or backslashes are
-        " UNC paths where the leading slashes are significant... In this case
-        " we split like this:
-        "   '//server/share/directory' -> ['//server', 'share', 'directory']
+        " UNC pathname.
         return split(a:path, '\%>2c[\/]\+')
       else
         " If it's not a UNC path we can simply split on slashes & backslashes.
         return split(a:path, '[\/]\+')
       endif
     else
-      " Everything except Windows is treated like UNIX until someone
-      " has a better suggestion :-). In this case we split like this:
-      "   '/foo/bar/baz' -> ['/', 'foo', 'bar', 'baz']
+      " Everything else is treated as UNIX.
       let absolute = (a:path =~ '^/')
       let segments = split(a:path, '/\+')
       return absolute ? insert(segments, '/') : segments
@@ -57,7 +76,10 @@ function! xolox#misc#path#split(path) " {{{1
 endfunction
 
 function! xolox#misc#path#join(parts) " {{{1
-  " Join a list of pathname components into a single pathname.
+  " Join a list of pathname components (the first and only argument) into a
+  " single pathname string. This is the counterpart to the
+  " `xolox#misc#path#split()` function and it expects a list of pathname
+  " components as returned by `xolox#misc#path#split()`.
   if type(a:parts) == type([])
     if s:windows_compatible
       return join(a:parts, xolox#misc#path#directory_separator())
@@ -78,9 +100,9 @@ function! xolox#misc#path#directory_separator() " {{{1
 endfunction
 
 function! xolox#misc#path#absolute(path) " {{{1
-  " Canonicalize and resolve a pathname, regardless of whether it exists. This
-  " is intended to support string comparison to determine whether two pathnames
-  " point to the same directory or file.
+  " Canonicalize and resolve a pathname, *regardless of whether it exists*.
+  " This is intended to support string comparison to determine whether two
+  " pathnames point to the same directory or file.
   if type(a:path) == type('')
     let path = a:path
     " Make the pathname absolute.
@@ -110,7 +132,8 @@ function! xolox#misc#path#absolute(path) " {{{1
 endfunction
 
 function! xolox#misc#path#relative(path, base) " {{{1
-  " Make an absolute pathname relative.
+  " Make an absolute pathname (the first argument) relative to a directory
+  " (the second argument).
   let path = xolox#misc#path#split(a:path)
   let base = xolox#misc#path#split(a:base)
   while path != [] && base != [] && path[0] == base[0]
@@ -123,9 +146,9 @@ endfunction
 
 
 function! xolox#misc#path#merge(parent, child, ...) " {{{1
-  " Join a directory and filename into a single pathname.
-  " TODO Use isabs()!
+  " Join a directory pathname and filename into a single pathname.
   if type(a:parent) == type('') && type(a:child) == type('')
+    " TODO Use xolox#misc#path#is_relative()?
     if s:windows_compatible
       let parent = substitute(a:parent, '[\\/]\+$', '', '')
       let child = substitute(a:child, '^[\\/]\+', '', '')
@@ -158,7 +181,8 @@ function! xolox#misc#path#commonprefix(paths) " {{{1
 endfunction
 
 function! xolox#misc#path#encode(path) " {{{1
-  " Encode a pathname so it can be used as a filename.
+  " Encode a pathname so it can be used as a filename. This uses URL encoding
+  " to encode special characters.
   if s:windows_compatible
     let mask = '[*|\\/:"<>?%]'
   elseif s:mac_os_x_compatible
@@ -171,7 +195,7 @@ endfunction
 
 
 function! xolox#misc#path#decode(encoded_path) " {{{1
-  " Decode a pathname previously encoded with xolox#misc#path#encode().
+  " Decode a pathname previously encoded with `xolox#misc#path#encode()`.
   return substitute(a:encoded_path, '%\(\x\x\?\)', '\=nr2char("0x" . submatch(1))', 'g')
 endfunction
 
@@ -188,7 +212,8 @@ else
 endif
 
 function! xolox#misc#path#is_relative(path) " {{{1
-  " Check whether a path is relative.
+  " Returns true (1) when the pathname given as the first argument is
+  " relative, false (0) otherwise.
   if a:path =~ '^\w\+://'
     return 0
   elseif s:windows_compatible
@@ -199,7 +224,7 @@ function! xolox#misc#path#is_relative(path) " {{{1
 endfunction
 
 function! xolox#misc#path#tempdir() " {{{1
-  " Create a temporary directory and return the path.
+  " Create a temporary directory and return the pathname of the directory.
   if !exists('s:tempdir_counter')
     let s:tempdir_counter = 1
   endif
diff --git a/autoload/xolox/misc/str.vim b/autoload/xolox/misc/str.vim
index 74a05aa..901696c 100644
--- a/autoload/xolox/misc/str.vim
+++ b/autoload/xolox/misc/str.vim
@@ -1,11 +1,17 @@
-" Vim auto-load script
+" String handling.
+"
 " Author: Peter Odding <peter@peterodding.com>
-" Last Change: June 14, 2011
+" Last Change: May 19, 2013
 " URL: http://peterodding.com/code/vim/misc/
 
-" Trim whitespace from start and end of string.
+function! xolox#misc#str#compact(s)
+  " Compact whitespace in the string given as the first argument.
+  return join(split(a:s), " ")
+endfunction
 
 function! xolox#misc#str#trim(s)
+  " Trim all whitespace from the start and end of the string given as the
+  " first argument.
   return substitute(a:s, '^\_s*\(.\{-}\)\_s*$', '\1', '')
 endfunction
 
diff --git a/autoload/xolox/misc/timer.vim b/autoload/xolox/misc/timer.vim
index 151972d..d7fc32d 100644
--- a/autoload/xolox/misc/timer.vim
+++ b/autoload/xolox/misc/timer.vim
@@ -1,6 +1,7 @@
-" Vim auto-load script
+" Timing of long during operations.
+"
 " Author: Peter Odding <peter@peterodding.com>
-" Last Change: March 15, 2011
+" Last Change: May 19, 2013
 " URL: http://peterodding.com/code/vim/misc/
 
 if !exists('g:timer_enabled')
@@ -13,24 +14,33 @@ endif
 
 let s:has_reltime = has('reltime')
 
-" Start a timer.
-
-function! xolox#misc#timer#start()
+function! xolox#misc#timer#start() " {{{1
+  " Start a timer. This returns a list which can later be passed to
+  " `xolox#misc#timer#stop()`.
   if g:timer_enabled || &verbose >= g:timer_verbosity
     return s:has_reltime ? reltime() : [localtime()]
   endif
   return []
 endfunction
 
-" Stop a timer and print the elapsed time (only if the user is interested).
-
-function! xolox#misc#timer#stop(...)
+function! xolox#misc#timer#stop(...) " {{{1
+  " Show a formatted debugging message to the user, if the user has enabled
+  " increased verbosity by setting Vim's ['verbose'] [verbose] option to one
+  " (1) or higher.
+  "
+  " This function has the same argument handling as Vim's [printf()] [printf]
+  " function with one difference: At the point where you want the elapsed time
+  " to be embedded, you write `%s` and you pass the list returned by
+  " `xolox#misc#timer#start()` as an argument.
+  "
+  " [verbose]: http://vimdoc.sourceforge.net/htmldoc/options.html#'verbose'
+  " [printf]: http://vimdoc.sourceforge.net/htmldoc/eval.html#printf()
   if (g:timer_enabled || &verbose >= g:timer_verbosity)
     call call('xolox#misc#msg#info', map(copy(a:000), 's:convert_value(v:val)'))
   endif
 endfunction
 
-function! s:convert_value(value)
+function! s:convert_value(value) " {{{1
   if type(a:value) != type([])
     return a:value
   elseif !empty(a:value)
@@ -49,7 +59,10 @@ endfunction
 
 let s:units = [['day', 60 * 60 * 24], ['hour', 60 * 60], ['minute', 60], ['second', 1]]
 
-function! xolox#misc#timer#format_timespan(ts)
+function! xolox#misc#timer#format_timespan(ts) " {{{1
+  " Format a time stamp (a string containing a formatted floating point
+  " number) into a human friendly format, for example 70 seconds is phrased as
+  " "1 minute and 10 seconds".
 
   " Convert timespan to integer.
   let seconds = a:ts + 0
diff --git a/autoload/xolox/session.vim b/autoload/xolox/session.vim
index 55e1520..6ce5be6 100644
--- a/autoload/xolox/session.vim
+++ b/autoload/xolox/session.vim
@@ -1,11 +1,11 @@
 " Vim script
 " Author: Peter Odding
-" Last Change: May 13, 2013
+" Last Change: May 20, 2013
 " URL: http://peterodding.com/code/vim/session/
 
-let g:xolox#session#version = '2.3'
+let g:xolox#session#version = '2.3.1'
 
-call xolox#misc#compat#check('session', 3)
+call xolox#misc#compat#check('session.vim', g:xolox#session#version, 7)
 
 " Public API for session persistence. {{{1
 
diff --git a/doc/session.txt b/doc/session.txt
index 270fd63..a98d456 100644
--- a/doc/session.txt
+++ b/doc/session.txt
@@ -457,8 +457,8 @@ If you like the script please vote for it on Vim Online [12].
                                                                *session-license*
 License ~
 
-This software is licensed under the MIT license [13]. Copyright 2013 Peter
-Odding <peter@peterodding.com>.
+This software is licensed under the MIT license [13]. Š 2013 Peter Odding
+<peter@peterodding.com>.
 
 ===============================================================================
                                                          *sample-session-script*