Help: Right-align command names

To aid the readability of the help output, align the dashes vertically
so the descriptions are in a uniform place.

The resulting output now looks like this:

                    <git_sha> – Generate a commit URL based on the given SHA.
    git remote set origin URL – Set the git remote URL for this channel.
                         help – Show a list of available bot commands.

1 files changed, 6 insertions, 1 deletions

diff --git a/src/Plugin/Help.hs b/src/Plugin/Help.hs
index 470dd33..a141745 100644
--- a/src/Plugin/Help.hs
+++ b/src/Plugin/Help.hs
@@ -19,7 +19,12 @@ help = Plugin
 helpAction :: PluginAction
 helpAction _ = do
     return $ Right $ T.intercalate "\n"
-        [command p `T.append` " – " `T.append` description p | p <- plugins]
+        [T.justifyRight longestCommandLen ' ' (command p)
+            `T.append` " – "
+            `T.append` description p
+        | p <- plugins]
+  where
+    longestCommandLen = foldr (max) 0 (map (T.length . command) plugins)
 
 plugins :: [Plugin]
 plugins = PL.plugins ++ [help]