Add packed-ref handling

This reverts commit 21b6dd7aee.

Closes https://github.com/tpope/vim-fugitive/issues/726

README.markdown

@@ -11,8 +11,8 @@ Vim's diff handling capabilities to stage a subset of the file's
 changes.
 
 Bring up the output of `git status` with `:Gstatus`.  Press `-` to
-`add`/`reset` a file's changes, or `p` to `add`/`reset` `--patch` that
-mofo.  And guess what `:Gcommit` does!
+`add`/`reset` a file's changes, or `p` to `add`/`reset` `--patch`.  And guess
+what `:Gcommit` does!
 
 `:Gblame` brings up an interactive vertical split with `git blame`
 output.  Press enter on a line to edit the commit where the line
@@ -55,15 +55,13 @@ and `Git!` to open the output of a command in a temp file.
 
 ## Installation
 
-If you don't have a preferred installation method, I recommend
-installing [pathogen.vim](https://github.com/tpope/vim-pathogen), and
-then simply copy and paste:
+If you don't have a preferred installation method, one option is to install
+[pathogen.vim](https://github.com/tpope/vim-pathogen), and then copy
+and paste:
 
     cd ~/.vim/bundle
     git clone git://github.com/tpope/vim-fugitive.git
-
-Once help tags have been generated, you can view the manual with
-`:help fugitive`.
+    vim -u NONE -c "helptags vim-fugitive/doc" -c q
 
 If your Vim version is below 7.2, I recommend also installing
 [vim-git](https://github.com/tpope/vim-git) for syntax highlighting and

doc/fugitive.txt

@@ -63,12 +63,32 @@ that are part of Git repositories).
                         to commit, |:Gstatus| is called instead.  Unless the
                         arguments given would skip the invocation of an editor
                         (e.g., -m), a split window will be used to obtain a
-                        commit message.  Write and close that window (:wq or
-                        |:Gwrite|) to finish the commit.  Unlike when running
-                        the actual git-commit command, it is possible (but
-                        unadvisable) to muck with the index with commands like
-                        git-add and git-reset while a commit message is
-                        pending.
+                        commit message, or a new tab if -v is given.  Write
+                        and close that window (:wq or |:Gwrite|) to finish the
+                        commit.  Unlike when running the actual git-commit
+                        command, it is possible (but unadvisable) to alter the
+                        index with commands like git-add and git-reset while a
+                        commit message is pending.
+
+                                                *fugitive-:Gmerge*
+:Gmerge [args]          Calls git-merge and loads errors and conflicted files
+                        into the quickfix list.  Opens a |:Gcommit| style
+                        split window for the commit message if the merge
+                        succeeds.  If called during a merge conflict, the
+                        conflicted files from the current index are loaded
+                        into the quickfix list.
+
+                                                *fugitive-:Gpull*
+:Gpull [args]           Like |:Gmerge|, but for git-pull.
+
+                                                *fugitive-:Gpush*
+:Gpush [args]           Invoke git-push, load the results into the quickfix
+                        list, and invoke |:cwindow| to reveal any errors.
+                        |:Dispatch| is used if available for asynchronous
+                        invocation.
+
+                                                *fugitive-:Gfetch*
+:Gfetch [args]          Like |:Gpush|, but for git-fetch.
 
                                                 *fugitive-:Ggrep*
 :Ggrep [args]           |:grep| with git-grep as 'grepprg'.
@@ -84,6 +104,11 @@ that are part of Git repositories).
                         previous commits rather than previous file revisions
                         are loaded.
 
+:{range}Glog [args]     Use git-log -L to load previous revisions of the given
+                        range of the current file into the quickfix list.  The
+                        cursor is positioned on the first line of the first
+                        diff hunk for each commit.
+
                                                 *fugitive-:Gllog*
 :Gllog [args]           Like |:Glog|, but use the location list instead of the
                         quickfix list.
@@ -195,32 +220,38 @@ that are part of Git repositories).
 :[range]Gblame [flags]  Run git-blame on the given range.
 
                                                 *fugitive-:Gbrowse*
-:[range]Gbrowse         If the remote for the current branch is on GitHub,
-                        open the current file, blob, tree, commit, or tag
-                        (with git-web--browse) on GitHub.  Otherwise, open the
-                        current file, blob, tree, commit, or tag in
-                        git-instaweb (if you have issues, verify you can run
-                        "git instaweb" from a terminal).  If a range is given,
-                        it is appropriately appended to the URL as an anchor.
+:Gbrowse                Open the current file, blob, tree, commit, or tag
+                        in your browser at the upstream hosting provider
+                        indicated by the "origin" remote.  If a range is
+                        given, it is appropriately appended to the URL as an
+                        anchor.
 
-                        To use with GitHub FI, point g:fugitive_github_domains
-                        at a list of domains:
->
-                        let g:fugitive_github_domains = ['https://example.com']
-~
-:[range]Gbrowse!        Like :Gbrowse, but put the URL on the clipboard rather
-                        than opening it.
+                        Upstream providers can be added by installing an
+                        appropriate Vim plugin.  For example, GitHub can be
+                        supported by installing rhubarb.vim, available at
+                        <https://github.com/tpope/vim-rhubarb>.  (Native
+                        support for GitHub is currently included, but that is
+                        slated to be removed.)
 
-:[range]Gbrowse {revision}
-                        Like :Gbrowse, but for a given |fugitive-revision|.  A
+                        If no upstream support is available, a local instance
+                        of git-instaweb will be started and used instead.
+
+:Gbrowse {revision}     Like :Gbrowse, but for a given |fugitive-revision|.  A
                         useful value here is -, which ties the URL to the
                         latest commit rather than a volatile branch.
 
-:[range]Gbrowse [...]@{remote}
-                        Force using the given remote rather than the remote
+:Gbrowse [...]@{remote} Force using the given remote rather than the remote
                         for the current branch.  The remote is used to
                         determine which GitHub repository to link to.
 
+:{range}Gbrowse [args]  Appends an anchor to the URL that emphasizes the
+                        selected lines.  You almost certainly want to give a
+                        "-" argument in this case to force the URL to include
+                        an exact revision.
+
+:[range]Gbrowse! [args] Like :Gbrowse, but put the URL on the clipboard rather
+                        than opening it.
+
 MAPPINGS                                        *fugitive-mappings*
 
 These maps are available everywhere.