+ hg help
hg commands:

 add         add the specified files on the next commit
 addremove   add all new files, delete all missing files
 annotate    show changeset information per file line
 cat         output the latest or given revision of a file
 commit      commit the specified files or all outstanding changes
 diff        diff working directory (or selected files)
 export      dump the changeset header and diffs for a revision
 forget      don't add the specified files on the next commit
 heads       show current repository heads
 help        show help for a given command or all commands
 history     show the changelog history
 init        create a new repository or copy an existing one
 log         show the revision history of a single file
 manifest    output the latest or given revision of the project manifest
 parents     show the parents of the current working dir
 patch       import an ordered set of patches
 pull        pull changes from the specified source
 push        push changes to the specified destination
 rawcommit   raw commit interface
 recover     roll back an interrupted transaction
 remove      remove the specified files on the next commit
 serve       export the repository via HTTP
 status      show changed files in the working directory
 tags        list repository tags
 tip         show the tip revision
 undo        undo the last transaction
 update      update or merge working directory
 verify      verify the integrity of the repository
+ hg add -h
hg add: option -h not recognized
hg add [files]

add the specified files on the next commit
+ hg help diff
hg diff [-r A] [-r B] [files]

 -r --rev 
   revision

diff working directory (or selected files)
+ hg help foo
hg: unknown command foo