Add more matchers to the tab completion DSL

[georgebrock]

Various rules in the completions file use the a less specific matcher to represent a specific value. In many cases we use the $anything matcher, e.g.

log $opt*
  --tags $anything?

These could be replaced with more specific matchers, e.g.

log $opt*
  --tags $tag?

The following things could be useful:

• $stash for the names of Git stashes, e.g. stash show $stash
• $tag for the names of Git tags, e.g. log --tags $tag
• $dir_path for paths that should always be a directory not a file, e.g. :cd $dir_path
• $branch for revisions that should always be a branch name, e.g. branch --delete $branch
• $var_name for the names of gitsh variables, e.g. :set $var_name $anything
• $config_var_name for the names of Git config variables, e.g. config $config_var_name
• $author for names or emails of contributors to the repo, e.g. log --author $author
• $modified_path for paths that have uncommitted changes, e.g. add $modified_path
• $ctag for program symbols defined in a ctags(1) file, e.g. log -S $ctag

[benknoble]

Not sure if this is the right place to ask, but could gitsh also support completing the single- and double-dash option names? I get this in bash (can't seem to pin down from where though--could be the git completion that ships with homebrew git, or from homebrew bash-complete).

[georgebrock]

@benknoble The currently released version doesn't, but the master branch does. It will be included in the next release.

[georgebrock]

I think $branch and $tag were the most important items on this list. Now they're done, I'm going to move this issue from v0.14 to v1.0.