Fix compdef commands in git plugin

The command `compdef command=git` returns an error in some cases, the
appropriate command is `compdef _git command`.

Fixes #5442

plugins/git/git.plugin.zsh

@@ -76,7 +76,7 @@ alias gcd='git checkout develop'
 alias gcmsg='git commit -m'
 alias gco='git checkout'
 alias gcount='git shortlog -sn'
-compdef gcount=git
+compdef _git gcount
 alias gcp='git cherry-pick'
 alias gcpa='git cherry-pick --abort'
 alias gcpc='git cherry-pick --continue'
@@ -159,7 +159,7 @@ alias ghh='git help'
 alias gignore='git update-index --assume-unchanged'
 alias gignored='git ls-files -v | grep "^[[:lower:]]"'
 alias git-svn-dcommit-push='git svn dcommit && git push github master:svntrunk'
-compdef git-svn-dcommit-push=git
+compdef _git git-svn-dcommit-push=git
 
 alias gk='\gitk --all --branches'
 compdef _git gk='gitk'