buffers will not persist after they're closed.

Plugins' names which contain '../', '$HOME', '%h', '..\', etc.
can be dangerous.
Use a sensible whitelist for plugin names and prevent its expansion.

All global variables that are not part of the public API (mentioned in the
documentation) are turned into autoload variables.  This is intended to give
all global variables defined by Vundle.vim a common prefix.  The variable
g:default_git_proto is part of the public API and is therefor not changed.
This is the only exception.

Changed:
   g:bundle_dir            -> vundle#bundle_dir
   g:bundles               -> vundle#bundles
   g:updated_bundles       -> vundle#updated_bundles
   g:vundle_lazy_load      -> vundle#lazy_load
   g:vundle_log            -> vundle#log
Unchanged:
   g:default_git_proto

If it was loaded, unload the log buffer before editing it.  Otherwise the
editing command can "hang" if the user has `set hidden`.

This problem was originally discovered with the VundleChangelog command and
the analogous fix was applied in 7d9b10.  See github issue #468 for more.

These variables only occur in one file each.  By making them script local
variables this is "documented" in the code.  At the same time the global
namespace is polluted less.

Changed:
    g:bundle_names          -> s:bundle_names
    g:vundle_last_status    -> s:last_status
    g:vundle_log_file       -> s:log_file
    g:vundle_view           -> s:view

The command `silent pedit ...` was causing trouble if the user had `set
hidden`.  Now we `bdelete` the changelog buffer before editing it anew.

Vundle manipulates plugin folders by `cd`-ing into them and calling git
via `call system(cmd)`. This doesn't work if GIT_DIR is set as a global
environmental variable (most commonly by a git hook). Since there is no
use case in which Vundle should respect GIT_DIR, this PR preemptively
precedes all git calls with `unset GIT_DIR; `. This makes the git calls
behave as expected without unsetting GIT_DIR in the environment beyond
vim.

Rearranging rtp so that **all** default directories appear first has the
undesired side effect of not allowing plugins to override default syntax
files.

This changeset limits the rearrangement of the rtp to simply making sure
the first directory in the default runtimepath appears first in also in
the runtimepath after Vundle has finished manipulating it.

This should keep the original bugs fixed and should eliminate the
aforementioned undesired side effect.

Fixes #430
Fixes #456

Suggested by @ikurcubic

So it can be reused.

Fixes #441

If one had this plugin:

Plugin 'foo/bar'

And now switches to another one with the same name:

Plugin 'baz/bar'

Recognise this scenario and replace the old plugin with the new one,
rather than silently assuming they are the same.

Fixes #367 #48 #183 #400

* Add modelines to all code/doc files excluding README.md.  The modeline used is: `" vim: set expandtab sts=2 ts=2 sw=2 tw=78 norl:`
* Rename links with /vundle to /Vundle.vim, seems to confuse some people with redirect.
* Remove duplicates from Quickstart, add example of `name` flag.
* Add link to Tips page by @Lucc .
* Change help maintain vundle link directly to the new one.
* README.md line number links updated.

Note: Users with bundle/vundle need to rename vundle to Vundle.vim to use test files. Vundle will continue to function otherwise.

Fixes #413.
Fixes #438.

- Complete the code documentation effort started by @lucc
- Remove some judgemental comments ✨
- Remove comments pertaining to things that should be opened as issues
- Boxed ❗

Also add some FIXME markers in places where the code needs more
explanation.

New supported option called 'pinned' for the Plugin command. When set to
1, the plugin is added to rtp but no install/upgrade operation is
performed.

It not only allows vundle to do rtp management of plugins on VCS other
than git, it also allows leaving plugins that had previously been
managed by vundle in the current state, with no further updates.

Fixes #24, #397

Prevents error 150 when user has doc/* in wildignore

Fixes #112

Still keep :Bundle backwards compatible.

- closes many issues )

Bundle configuration options that are inferred from the bundle specs
overwrite user provided ones. This used to prevent users from changing
the name of directory where the cloned bundle should go, for instance.

Keep the user provided options with a preference over inferred ones.

Should fix #231.

- resolve introduced in 08e9894d2 resolves only bundle dir
- so '/doc/' dir doesn't loose its trailing slash

Helptags seems to fail if some of the path components it receives are
symlinks. So resolve the symlink when calling helptags.

In Windows, some users set the Cygwin shell as their Vim shell, make
Vundle consider this when deciding which flavour of commands to run when
cloning. Roughly check if the shell contains `sh` in it, and assume a
Unix shell, even when on Windows.

Failures in :helptags commands for individual bundles were logged but
the error were not propagated to the installer.

Warn the user when a leading or trailing space is found in one the
bundle specs they have configured using the Bundle command.

The wildignore setting affects the behaviour of the `= shorthand, so
this changeset replaces the last remaining use of such construct with a
call to exec.

Certain wildignore values prevented the various logs from being
viewable.

Fixes #249

inspired by
https://github.com/gmarik/vundle/pull/228 and
https://github.com/gmarik/vundle/pull/172

Vim patch #445 changed shell escaping and introduced incompatabilities for vundle.
Now vundle only escapes joined commands with double quotes on windows when shellxquote is not set to '('.
This workaround closes https://github.com/gmarik/vundle/issues/146 - the mentioned workaround
is no longer needed, but it does not break a vim configurations which contains "set shellxquote=".

DRY shell escaping and modified (hopefully) all relevant places.

- causes #203

This reverts commit 1e140c9f6b.

- not all versions of vim 7.2 support the extra argument for glob*(),
  only those compiled with patch 51

- make it append only (instead both append + prepend)
- which draws *_rm_a and *_add_a useless as &rtp order gets preserved
- benefits: simpler, faster, less code

The codepath does not appear to have been tested; mv on Win32 is move,
and substitute has 4 arguments instead of 3.

When vundle installed as git submodule, git create file '.git' instead of
directory '.git'.

And vundle cannot update by self :(

With just `git clone`, submodules are not grabbed. This is an issue for
certain plugins, such as 'kevinw/pyflakes-vim' that requires a pyflakes
submodule

- add /d switch to cd command to perform drive change
- enclose joined commands with quotes