Further git completion improovements

In detail:
gup - now completes with remotes like git fetch would
gdv - got git diff completions
gc/gca - now zsh will suggest files in staging area
gba - suggestions as for git branch

plugins/git/git.plugin.zsh

@@ -6,24 +6,24 @@ compdef _git gst=git-status
 alias gl='git pull'
 compdef _git gl=git-pull
 alias gup='git fetch && git rebase'
-compdef gup=git
+compdef _git gup=git-fetch
 alias gp='git push'
 compdef _git gp=git-push
 alias gd='git diff | mate'
 # WTF is mate??
 compdef _git gd=git-diff
 alias gdv='git diff -w "$@" | vim -R -'
-compdef gdv=git
+compdef _git gdv=git-diff
 alias gc='git commit -v'
-compdef gc=git
+compdef _git gc=git-commit
 alias gca='git commit -v -a'
-compdef gca=git
+compdef _git gca=git-commit
 alias gco='git checkout'
 compdef _git gco=git-checkout
 alias gb='git branch'
 compdef _git gb=git-branch
 alias gba='git branch -a'
-compdef gba=git
+compdef _git gba=git-branch
 alias gcount='git shortlog -sn'
 compdef gcount=git
 alias gcp='git cherry-pick'